Bericht: Motoruberhohlung E28S M5

Dieses Bericht beschreibt der zerlegung und ausbau von dem Motor meines E28 M5 nachdem anfang Juni 2008 ein verbrenntes Ventil festgestellt wurde. Weiterhin beschreibt dieses Bericht der fehler-analyse und der neuaufbau zwischen Marz und September 2009.

Diese bericht ist primar geschrieben fur http://www.m5board.com, weswegen es in die Englische sprache geschrieben ist. Leider fehlt mir der zeit um dies auch in Deutsch zu tun, aber die bilder allein sind schin die muhe von das anschauen wert.

Viel spass.

E28S M5’s are like a good glass of whine. For the right occasion that is. I had one for last Sunday when I had to travel to Wittlich in Rheinland-Pfalz, a state in the West of Germany. Also the Nurburgring is part of this state that has long since been governed by leftist politicians. Left does not necessarily mean green, especially not with the smell of money.

My main goal were the returning participants of the Europarit who have to follow a strict route during which they have to carry out tasks that determine the overall classifications. This event is not about speed, but more about regularity, precise navigation and a sharp eye for objects that have to be recognized. Since 1994 I have been an official for this event, up until 2001 for the full five days and after 2002 for the first or the last day only. I have used my E34S M5 for my Europarit related trips since 1999, but this year, I preferred the E28S provided the weather is stable and dry. One doesn’t want to mix a good whine with water after all.

With the weather forecast all showing green lights I drove off at around half past seven. The first forty kilometers over the speed limited Dutch highway were used for a gentle warming up before entering Germany where I filled the empty fuel tank in Gronau, just across the border near Enschede. With a working water-temperature gauge, I drove off towards the Oberhausen straight (A31) towards Bottrop. Traffic on this Sunday morning was low, and I could cruise easily between 190km/h and 200km/h. A Dutch registered Volvo V70 tried to follow me during the last few kilometers on the A31, but lost on acceleration.

The A3 towards Cologne went rather uneventful; a few small surprised faces in a Swiss registered Audi A6 3.2FSI when they discovered that they could not shake off that old BMW behind them, but that was about it. For the rest, I cruised between 4500RPM and 5000RPM until closing in on Leverkussen were I turned southwest towards Koblenz. I took it easy up until passing Cologne after which the speed limits were lifted and I entered a lovely highway section were I could cruise at roughly 200km/h for a prolonged period of time. Just before Euslichen, I approached an E46 320d from behind and we both had to brake for another car that changed lane with 140km/h. The driver in the 320d apparently thought that he could shake of that old E28, but he probably missed the M5 badge in the grille as he kept driving in front of me. When the 320d finally reached 180km/h, it moved to the right, after which I passed him with an intimidating soundtrack from the screaming M88/3. I just had enough time to see a glimpse of three very surprised occupants in the E46.

I had a rendez vouz with member Stevie on the B258 between 10:00 and 10:30 so I turned west on the A1 towards Blankenheim and Trier near Bliesheim. Up until now, I just took it easy with two or three full throttle bursts into the 200km/h range. Unlike the E34S, the E28S has a longer diff with a 3,73:1 ratio, and thus does not have the need to rev as high as many S38 engines with the 3,91:1 differential. When I drove through the long right autobahn curve towards the A1, I suddenly noticed a small surge in power at roughly 3200RM. It quickly disappeared once accelerating towards cruising speed of 180km/h till 200km/h when I approached another Audi A6 from behind. Its driver didn’t fancy an old E28 tailing him, but he had no choice other then moving to the right in the end.

Up until so far, everything went well and I almost forgot about the small power surge at Bliesheim. When I left the A1 and entered the B258, the engine still ran fine with the water-temperature gauge just a little left from the middle. But when I approached the rendez-vouz point on the B258, I noticed a slight hesitation between 2000RPM and 3000RPM.

To be continued.

It was just 9:50 when I arrived at the rendez-vouz point alongside the B258. I let the engine idle and opened the hood to investigate the hesitation that I just noticed a few moments before. The symptoms can be described as coughing, as if one cylinder didn’t work anymore. I checked the exhaust, but could not find anything wrong. The color of the factory new exhaust had a light brown tint in it, but fortunately no black sediments so it looked OK. I manually operated the throttle lever to increase the engine speed after which the hesitation could not be noticed. I could hear a slight tick tough and thought of an ignition problem.

I decided to turn the engine off to cool it down and wait for Stevie who just had called to inform me that he just had entered the A1 at Bliesheim. I took a cup of coffee and used a sandwich and waited. After a while, I checked the oil in the engine; level and color were OK. I also did not see oil residue in the coolant. I started the engine once again and confirmed the problem.

Shortly before 10:30 I heard the typical scream of BMW’s most efficient products. A few moments later Stevie and Pieter arrived in a client’s CSL that had just been fitted with new performance brakes that needed to be braked-in first before entering a driving course. Upon arrival, I briefed Stevie about my problem that he investigated. This gave me the opportunity to check the exhaust whilst he raised the engine speed. Exhaust emissions were close to absent, but Stevie’s analysis was a leaking exhaust-gasket and or a broken shim in the valve-train.

Basically, I had two options. The safest would be to call one of the participants of the 2007 Alps tour who lives nearby. However, this meant that I could not make my appointment in time. That was not really an option unless the facts proved otherwise so I did weigh my options and decided to take a calculated risk. As long as I kept the engine speed above 3500RPM, the engine ran fine. I avoided full throttle conditions and kept engine speed below 4200RPM to avoid lean running conditions.

We arrived at our destination in Esch at around 11:30 in the morning. I asked Stevie and Pieter if they had seen any smoke coming from the exhaust, which they both said was not the case. I setup the checkpoint for the Europarit after which we waited for the participants. Our checkpoint was opened between 12:04 and 13:41, after which we could close it and those who have missed it will lose significant points for their ranking in the official classification. It’s a nice game between officials and participants, some of which know exactly when and were they are and how far they are of their ideal passing time. It’s not a speed contest, but more a regularity drive in combination with specific route tasks.

At roughly 13:30, most of the participants had found our checkpoint and it was time to investigate a little deeper. Stevie checked the spark plugs one by one, but gave all of them the all clear. There was not much what we could do, but after some deliberation, we decided that driving home was too much of a risk so I called the E34S heritage center in Meuspach to ask if I could leave my car in their workshop pending it to be transported back to Holland. Marion was very kind and offered that Mark would look at it. With Stevie leading the way, we drove off towards Adenau. We wanted to avoid that at first since this was the weekend of ‘Rock am Ring’, a rock festival that attracts 180000 partying visitors due too which the entire Nordschleife region looks like a war zone. Stevie knew a small country road from the A48 towards Meuspach, but even then, we had to drive through dozens of camps with drunk and comatized people. We arrived at Meuspach shortly after half past four. Mark quickly took a look and diagnosed ignition problems. Marion and Mark even attempted to find the fault on the spot, but eventually we said that it could wait until Monday.

As one of the other officials of the Europarit accompanied us, I could hop in and return to Holland, leaving the E28S in the good hands of Marion and her team (Mark and Guido).

To be continued.

Every classic M5 enthusiast knows what a factory replacement engine for these cars costs but it was a bit of a deja vu when I had to leave the E28S behind to avoid ruining it’s M88/3 engine. But I already had risked enough for wanting to fulfill to my obligations to my auto club.

In retrospect, this only was the second time that any of my BMW’s got me stranded and both times with ignition related problems. The E34S once broke a distributor cap in autumn of 2000 and now the E28S with similar problems, if only the distributor cap-and rotor is less then 2000km old. I did replace the ignition wiring on the E34S in the summer of 2004 as part of another ignition related problem that eventually turned out to be the distributor cap-and rotor. I did plan this for the E28S as well, but for a scientist approach not before I had found the source of the slight surging between 2000RPM and 3000RPM that the car always had suffered from, but that I managed to reduce to less then five percent of the original magnitude by replacing many parts, amongst others the ignition coil in 2005 and the airflow meter (AFM) in 2007.

The remainder of the power-surge proved difficult to find. I last checked the spark plugs last April and they were fine. I recently found the patches in the engine-wiring loom towards the temperature sender and temperature sensors and wanted to address that first before ordering new expensive parts for exclusion purposes only. With other words, I didn’t really mind someone else to take a look at this so after some thoughts I accepted the offer from Marion (Werner Bluhm Sport auto Gmbh) to investigate this.

When I walked into my office yesterday morning, I saw a note from Monday that I had to call back Marion. That note was left on a place where I would hardly find it hence the delay of me returning Marion’s phone call. She informed me that all was fine, but that it was a good decision to leave the car behind. She then forwarded me to Guido, her mechanic who briefed me the technical details.

It turned out to be an ignition problem after all. The individual leads between the distributor and the six spark plugs where all fine. They all measured identical with a series resistance of 5700Ohms plus or minus an insignificant tolerance. Also their insulation was OK. This confirmed the test results that Mark and I had achieved last Sunday. The problem was caused by the seventh lead between the ignition coil and the distributor cap.

Normally, the electrons flow from the negative potential (engine ground) to the high potential voltage source (ignition coil). When the engine is at TDC, the distance between the spark plug and the piston is at its smallest due to which the already highly compressed fuel/air mixture can ignite fully. The impedance of the HV leads functions as source impedance and thus limits the maximum peak current to roughly 5,5Amps with a 30kV ignition coil.

The seventh lead was broken at some point close to the connector shell of the ignition coil. It had developed an open contact that was small enough to break down under high voltages. This not only causes phase delays, but also adds a second order point in the system. In the time domain, an ignition pulse is small and may be considered as a dirac-pulse. Converted to the frequency domain (fourier analysis), this pulse has a wide spectrum with a small negative slope into the high frequency range. With other words, the frequency spectrum is likely to contain a point that matches the resonance frequency of the second order system due to which the ignition spikes rises to a value above the source voltage of the ignition coil. Granted, the 5700Ohms series resistance damps the Q-factor a bit, but even when only two, this equates to amplitude of 40-60kV, far to high for the insulation of the aging HV wiring, hence why Stevie could feel a discharge when touching the leads in Esch.

I did ask about the exhaust manifold gaskets, but according to Udo these were fine. Mark already thought so as his analysis was that they are not that old. I know the cylinder head has been replaced at some point in the cars life before I acquired it in April 2001 so this didn’t really surprise me. Ultimately it came down to that single wire that caused the break down. Fortunately this part was stocked by BMW AG so it only has to arrive, installed and tested.

However, I just had drafted the above summary when I heard some dreadfull news. Later more.

Oh well, Things got an opposite turn right now. The new HV lead didn't solve the problem so they started to fear for the worst and used an endoscope to check the combustion chambers.

To make a long story short:
1: cylinder head torn near cyl #6
2: burnt exhaust valve at cyl#4

An analysis doesn't make sense at the moment as this is just a summary that has been passed to me through my father, but this is bad news. Anyhow, I would like to thank Marion, Mark and Udo from Werner Bluhm sport auto Gmbh for their help and assistance.

In the mean time, I called a German BMW dealer just accross the border. I suspect they have shorter leads to BMW AG in Munich as my own dealer who has to use the Dutch dealer network. What I have been told is that all M88/3 engines have been sold, but demand is such that a new batch is currently in the make and just awaiting a few parts to complete. Estimated delivery time is five to eight weeks. Price will go up to 8580 Euro ex VAT. Core charge remains the same at 1600 Euro's for the old engine. The parts representaive could not mention a discount rate, but was prepared to give some when placing the order.

I just called my dealer. I did not tell about my own enquiry. Lets wait and see if these match. For 8580 Euro's, I will reinvestigate if a rebuild does make sense after all.

Update:

My dealer just confirmed the above information with exception of the delivery time:

Teilenummer: 11 00 2 149 425
Benenning: Austausch triebwerk
LO: 02/
Zusatz benennung: 356ED
Price: 8580 Euro ex VAT
Core charge: 1600 Euro
Estimated delivery time: two to three weeks

Knowing now that I have to allow five to eight weeks for a new engine to arrive, I have decided to step back for a while and remove the engine before the summer holidays. This has to be done regardless of my choice; rebuild or RMFD engine.

I am not blindfolded towards a RMFD engine as this choice also has its con's, but at the moment, a RMFD engine offers best best value in #231's current situation. I am not prepared to spend labour hours in a rebuild when I verify Udo's findings. According to him, the crack in cyl #6 has been there for a very long time. That statement may be seen as proof for my fears that the engine has been cost effectively rebuild by the PO.

One might argue that I should have removed the cylinder head after I have found the breakers inscriptions on the cyl-head. Very true, but on the other hand what would that have changed? The crack at cyl #6 is isolated from the loss of compression on cyl #4 (Udo confirmed that) so already long before Sunday the eight of June, the head was scrap metal.

I have avoided high revs throughout most of the trip. A M88/3 powered E28S M5 does not really need it with its low weight and 3,73:1 final drive allowing for up shifts at 6000RPM maximum. Even 250km/h true speed (what I did not achieve), means 6500RPM in fifth gear. I saw 6200RPM in fifth gear for a short moment at roughly 250km/h on the speedo. This is roughly 238km/h calculated true speed (5%).

Stevie suggested lean running conditions as well. During the last emissions check the value for hydrocarbons was on the high side and with that in mind, I now suspect that one or more valves were not OK. Maybe that the cleaning additives in the V-Power (100RON) have removed some of the contamination in the head exposing the bare metal on some already weak spots. With that in mind, I doubt that the last valve adjustment (3000km ago) has been performed properly. I will measure the valve clearance before removing the head to prove or reject that.

Maybe I will go for a rebuild, but it depends on the cost and benefits. I will compare cost of both variants and will not put blind faith in a BMW RMFD engine, but the basic principle remains that the cost of a rebuild should be less then the cost of a RMFD engine, regardless of who carries out the rebuild.

The expected delivery time is around September. Gives me plenty of time to remove the engine and strip it for a forensic analysis. I also enquired about the fuel that must be used since the M88/3 does not have a catalytic converter and must be run on Super leaded 98RON. I have received a TIS document that states:

Group:13: 13 01 98 (298)
Date: 04/1998
Region: Worldwide with exception of the USA and Canada.

1: All M10, M20, M30, M88 and S14 engines without cat or cat preparations:
(manufacturing date series-start until August 1984)

These can be used on Super unleaded provided that they have been run on Super leaded for a minimum of 60k km. In these cases, there is enough lead(-tetraethyl) on the valve seats that there is enough protection (memory effect) for the remainder of the cars service-life .

2: With less then 60k km and a more sportive driving style (high revs etc.), it is recommended to add an suitable additive for protection of the valves at refueling.

3: If on the engine subject to point 1, the cylinder head has been replaced by a part that is obtained through the BMW network after August 1984, unleaded fuel can be used without restrictions. The reason is that BMW changed the valve-seats to a ‘hard type’ for all production engines. This also applies for BMW RMFD engines.

4: As long as the valve seats of the cylinder heads of engines subject to point 1 have only been slightly grinded, the ‘memory-effect’ of the existing lead-oxid supply provides for a sufficient protection of the valve seats. In all other cases of a cylinder head overhaul, points 1 and 2 apply.

5: Exchanging the valve seats to the ‘hard type’ is not recommended by BMW because of the required tooling and cost compared to a new OE cylinder head.

6: With or without additives, the minimum octane rating of the engine specifications must be obeyed. If not, knocking can cause severe engine damage.

Udo from Werner Bluhm sportauto Gmbh was so kind to keep the broken parts and provide the results of the Compression test. Ironically, 13-6-2008 was on a Friday so I have received my portion of bad luck for a long time coming. :hihi:

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img252.jpg]

The broken connector of the HV-lead between the inition coil and distributor. This connector was connected to the distributer.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img250.jpg]

The black coloration is caused by the spark that occured after the entrapped air between the open wire and the connector ionised due to the very high dV/dt of the generated ignition pulse.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img251.jpg]

For the record. I inspected this wiring just a few weeks ago when I checked the condition of the spark plugs. At the time of that inspection they were all fine with the connector shell intact and an impedance of close to 1kOhms, thus matching the nominal specification. I am glad that I did replace the HV-wiring loom of my E34S M5 with a factory new part some time ago (August 2004). With the E28S M5, this joke will cost me a new engine.

I would like to express my gratitude to Marion Bluhm and her mechanic Udo from Werner Bluhm sportauto Gmbh on the 'gewerbepark Nurburg' for helping me out on that particular Sunday. They diagnosed the problem and tried to solve it by replacing the HV wire, but to no avail. They then carried out the compression test and inspected each cylinder with an endoscope. It was then concluded that the engine was broke and possibly beyond repair, at least compared to the nett cost of a RMFD engine.

Yesterday evening, I started with the removal of the auxiliary parts of the engine block, starting with the air-filter cabinet, intake plenum, buttervly valves and last but not least the valve cover. When carrying out such a complex job, it is important to work accurately and well organized. The basis for that are a lot of digital still images and ACDSee, an image browser that allows comments to be added to each and every picture.

Since an engine removal is much more work then for instance a plenum replacement, I use (re) closable plastic bags for all the bols, nuts and associated small parts. These bags are the redline in this little project. Each bag is labeled with a date, a number and a description of which function block it came from. Each bag is pictured and together with the precluding pictures is the basis of the documentation.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img255.jpg]

The removal of the air-filter cabinet and the intake plenum is rather straightforward. Also the throttle bodies is more or less routine so after roughly ninety minutes, the entire inlet-side was out of the car after which the inlet ports are exposed and visible.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img256.jpg]

I have seen many pictures of a rebuild and what strikes me most is the way the parts are being stored. I see pictures of parts in the car or on the floor, often without organization. I admit this is not always easy, but storage racks are relatively cheap and keep your project well organized.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img257.jpg]

Last but not least; I removed the valve cover to inspect the camshafts and measure the valve clearances.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img258.jpg]

To be continued.

I measured the valve clearances today, a procedure that is part of the forensic analysis. The engine is being stripped slowly but steadily. I also removed the viscous fan, the ignition distributor-and rotor, fan-shroud and the mounting flanges for the ignition part on the camshaft housing.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img261.jpg]

The engine has not been running since Friday the 13th, now three weeks ago. There still is a healthy oil-supply left on the cam lobes (Castrol TWS 10W60).

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img260.jpg]

The valve clearances for the inlet-side recorded:

[0.24;0.25] @ cyl #1, [0.29;0.27] @ cyl #2, [0.28;0.28] @ cyl #3,
[0.25;0.25] @ cyl #4, [0.29;0.29] @ cyl #5, [0.29,0.30] @ cyl #6

Apart from cyl #1 and cyl #4, these are OK, but despite the out of spec values for #1 and #4, this could not have caused the engine failure.

The valve clearances for the exhaust-side recorded:

[0.18;0.26] @ cyl #1, [0.21;0.14] @ cyl #2, [0.18;0.20] @ cyl #3,
[0.25;0.15] @ cyl #4, [0.21;0.21] @ cyl #5, [0.21,0.21] @ cyl #6

These are all out of range, but a closer look of the values of cylinder #4 results in a deviation of 0,1mm!! One of the valves of cylinder #2 even has a narrower clearance, but a smaller deviation (0,07mm). The large deviation for both exhaust valves of cylinder #4 matches the compression test results, but so does the to narrow valve-lash.

This leads to the question why these are so far out of range. I never checked them, but had this done as part of an inspection II service less then 3000km ago (Service records to proof). Admittedly, six years have past since then, but with moderate use these could not have changed so much in such a small mileage.

One may argue valve clearances changed due to one or more valves hitting into the overheated valve seats. Assuming that a deviation of more then 0,02mm indicates this, it is safe to assume that cylinders #3, #5 and #6 haven't suffered that much. Nevertheless, 0,21mm still is 0,09mm short of the minimum specification (0,30mm). I am going to check the service records to see if it specifies that shims have been replaced.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img262.jpg]

With other words, more questions arise. Maybe I get some when I have removed the head. But before I can reach the cylinder head, I have to remove the camshafts and their housing.

My goal for Monday evening was the removal of the camshaft housing. In order to do so, both camshafts need to be removed, which in itself is not that difficult. First, the upper chain guide has to be removed.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img280.jpg]

The removal of the upper chain provides for enough clearance to access the chain and the intake sprocket that needs to be removed first. As I am stripping the entire engine and anticipate on not using it again, there is no need to mark the timing positions.

Important though is to place the engine at TDC and loosen the six 10mm bolts of both camshaft sprockets with the tensioner in place as otherwise the cams will change position causing the valves to move.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img281.jpg]

The 10mm bolts on sprockets are secured with a locking plate that unfortunately was molested by the mechanic who replaced (Ahummm) the cylinder head a few years before I took over ownership of #231. Nevertheless, after roughly twenty minutes (ten of which needed to preparing the molested locking plate) the intake cam sprocket was out and in the labeled bag together with all the applicable parts.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img282.jpg]

To get access to camshaft-bearing shell of cylinder #6, camshaft housings’ back plate needs to be removed by unbolting the six 10mm bolts. Access is tight, but possible with a half open 10mm wrench. The four outer bolts were rather tight in contrast to the two bolts on the bottom side close to the middle line. These should have been torqued to spec, which is impossible with the engine still in the car.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img283.jpg]

Engine rebuilders have special tooling to lock the camshafts while loosening the 28 13mm bolts of the camshaft bearing shells. This is not required to strip the engine, but to avoid damaging the (long) camshafts due to the force of the compressed valve springs, it is important to loosen the nuts evenly over the entire length of the camshaft first. After the tension is gone, the bearing shells can be lifted and the camshafts removed. I kept the exhaust cam sprocket in place untill after removing the exhaust cam. This to achieve the required clearance for the mounting flange for the ignition rotor.

The bearing shells are marked by the manufacturer, allowing them to be identified when the engine is being reassembled.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img284.jpg]

With the camshaft out of the engine, the cam-housing can be removed.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img285.jpg]

To remove the cylinder head, the coolant must be tapped of first. I first placed a canister between the coolant reservoir and the engine block to drain the coolant from the reservoir and. This allows air to enter the system and thus levels out the pressure. This allows me to drain the coolant from underneath gently reducing the spill.

My coolant reservoir dates back to 2005 when it replaced the old unit that colored dark brown. After the reservoir was drained, I saw the same brown-dark coloration on the lower halve of the reservoir that is less then 2k km old. It definitely is not coloration, but more a residue of coolant reacting to an unknown substance.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img274.jpg]

With most of the coolant in the bucket, I removed the water pipes on the exhaust and front side. The piping on the exhaust side is bolted to the cylinder head with twelve M10 bolts that are not that difficult to reach.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img273.jpg]

I already measured the chain lash before checking the valve clearances. This can be done by measuring the distance between the TDC marks on the vibration damper and the timing-chain cover. Note that the camshafts must be positioned at TDC first.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img275.jpg]

The distance between both TDC marks measured ~1cm, not ideal, but according to one of the members of the German E34 M5 forum this is within tolerance. I can’t tell as I haven’t found any info from BMW for that matter.

With the removal of the water pipes, one gets access to the M88/3 exhaust headers. Each header is bolted to the cylinder head with four 9mm copper nuts, some of which are difficult to access with the engine in the car. Not that this is impossible, but it is time consuming and requires some creativity with sockets, extensions, ratchets and wrenches.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img276.jpg]

The upper twelve nuts are not that much of a problem. The lower twelve are a serious challenge, especially those from cylinders #2, #3, #4 and #5. I managed to remove all but one. The last one, from cylinder #4 seems impossible, but I suspect that with a half open 9mm bended wrench this is possible from above.

I also noticed that the lower twelve 9mm nuts where significantly less tight that the upper twelve nuts. From a disassembly point of view, this is an advantage, but not so for the overall quality of the work.

Some of you may have recognized similarities between my working-method and that from Eric Christie during the engine rebuild of his E34S M5 HC91 model back in 1999. He also removed the head prior to lifting the engine out of the car. I haven’t reached that point (yet).

I still had to remove the last of the twenty-four nine millimeter nuts from the exhaust-header. As said, these are a real PITA; I needed 2.5hours to get them all off.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img291.jpg]

After the exhaust manifold nuts, I removed the two 5mm inside hex nuts at the front of the engine and last but not least the fourteen head-bolts. I used a torque wrench to limit the force to 150Nm, but what surprised me was the variance in the force that I needed to apply for all the head bolts. Some where pretty tight, whilst one in particular was rather loose.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img290.jpg]

The fourteen head bolts before storage in a sealed bag. These are special bolts that only need to be torqued to spec once, so there is no need to remove the camshafts and the cam-housing after the engine has been reassembled.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img292.jpg]

After I disconnected the last two coolant hoses, I lifted the cylinder head out of the car for a closer inspection.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img293.jpg]

Some coolant had leaked into the fifth cylinder, but I quickly removed the spill.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img294.jpg]

The condition of the cylinder head gasket surprised me as it came out in one piece with no damages at all. A visual inspection of the pistons and the cylinders also didn’t yield any defects. No scores, no molten pistons, no signs of the valves hitting the pistons. Only some carbon build up, but that is all.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img295.jpg]

I don't think that the footprint on the pistons is caused by a physical contact betwene the intake valves and the pistons. The valves themsleves also show no sign of any impact so I assume that this is the cleaning effect of additives in high quality fuel types that must be used for running the M88/S38/S14 engines.

To be continued.

With the cylinder head on the bench, it was time for a closer inspection. Prior to placing it upside down, I first removed two hose brackets on the inlet side and the water-pipe on the back, both of which are straightforward.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img300.jpg]

I anticipated for a mess in the combustion chambers and as expected we spotted the problem at first glance. Let’s zoom-in on cylinder #4, the one that lost compression.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img301.jpg]

Looks obvious to me. Strangely, the exhaust valves from cylinder #4 show the same tint and coloration as those from cylinder #1, #2 and #6. Particularly cylinder #3 looks very much different then the rest.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img302.jpg]

The exhaust valves of cylinder #3 have colored almost white and not the brownish tint like the rest of them. With other words, especially these valves have been far too hot. We decided to remove the burnt exhaust valve of cylinder #4 and one from cylinder #3.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img303.jpg]

Both exhaust valves show a significant amount of carbon deposits alongside the valve-stem. This also applies for the other ten exhaust valves still in the cylinder head (inspection through the exhaust ports).

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img308.jpg]

The exhaust valve of cylinder #4 doesn’t seem to have been broken off so I assume that the missing part fully burnt and left the engine through the exhaust-ports. I could not find any traces inside the cylinders or on the pistons. Let’s take a closer look to the valve-seat of the removed exhaust valve of cylinder #3. Its exhaust valves are significantly more white then the rest and thus had to endure much higher temperatures.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img304.jpg]

Clearly visible is the difference in contrast on the valve seat. I expected a monotone light-tint with little variation in contrast. Instead roughly halve the surface area is dark increasing the thermal resistance of the valve seat. This significantly reduces cooling capacity and thus the valve runs significantly hotter. I suspect that the exhaust valves of cylinder number #3 have been replaced before and that the valve and seats where not grinded properly. The valve seat of the broken valve from cylinder #4 looks very different with almost no difference in contrast. And just this one has been burnt.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img306.jpg]

A closer inspection of the combustion chamber from cylinder #6 reveals the cracks between the exhaust valves and between the exhaust-and inlet valves.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img307.jpg]

All the combustion chambers show these cracks, albeit one is thinner then the other. I know that some people don’t object to these cracks, but I for one am critical.

It is time to reflect back and line up the facts:

[1]: Ignition wiring loom failed
[2]: OT mark on the vibration damper is ~1cm of from the OT mark on the timing chain cover.
[3]: Brown residue got in the coolant reservoir
[4]: Valve clearance of the exhaust valves significantly out of specified range.
[5]: Valve clearance of the intake valves partially out of specified range.
[6]: Exhaust valve of cylinder #4 burnt
[7]: Exhaust valve of cylinder #3 overheated.
[8]: Cracks in the combustion chamber
[9]: Lot’s of carbon build-up on the exhaust valve stems and the exhaust ports.

Given the fact that I have not seen impact damage on the valves and pistons, I rule out [2]. I also rule out [1] as a main cause, although it may played a minor role with [4] ad [9].

I think that [9] is the cause of [6] and that a glowing carbon particle was too much for the exhaust valve. When looking back to the 8th of June, I suspect that the valve collapsed whilst entering the A1 towards Blankenheim when I noticed the power surge. Given the fact that the exhaust valve stems of the other exhaust valves except those from cylinder #3 looked identical to the broken exhaust valve of cylinder #4, I now think that the others would have collapsed sooner or later.

Although it may seem strange that the exhaust valves of cylinder #3 didn’t break down earlier, I suspect that these have been replaced by the previous owner as part of a cost effective repair with the intention of selling the car. I also think that the cracks date back to that era (1995-2000).

Let’s play advocate of the devil and reflect back on the options.

1: New RMFD engine.
2: Full rebuild.
3: New cylinder head on the current engine block.
4: Repair cylinder head on the current engine block.
5: S/H engine.

engine block

Given the fact that I could not see any visual damage during the inspection of the block, it may very well be possible that it is in a fine condition. I am not that naïve to think that a visual inspection is enough to determine usability. With other words, that can only be decided after a specialist inspection. IMHO, measuring the M88 engine block is what any machine shop can do.

If the pistons measure well within specification and the bores are OK, I can do with replacing the main-bearings and con-rod bearings including the required machine work of the crankshaft (if necessary). If any of the pistons measure out of specification, IMHO all six of them have to be replaced.

cylinder head

I have summarized the visual damage rather well I think. Add to that; I have the advantage of knowing that member Robinson bought a S/H head from a well-known Dutch breaker to repair the engine of his E34S HD91 model a few years ago. I hope Robinson doesn’t mind that I post a picture of that cylinder head that was taken shortly after he received it.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img299.jpg]

I knew that he complained about the condition of that cylinder head and tried to get his money back or at least have it replaced with a good cylinder head, but to no avail so he decided to use it nonetheless. He recently attested in this thread that that head failed and needs to be replaced after 40k km.

With other words, leaving the cracks unattended is naïve and stupid. A befriended mechanic helped me with removing the valves using his special tool and he said that he has seen a lot of such damage on a wide variety of road cars and that the machine shop doesn’t object to them. Well I do, at least for this engine.

Let’s revert back to the combustion chamber of the cylinder head of my E28S. The green arrows point to the cracks that are similar to Robinsons example. The yellow arrow doesn’t point to a crack, but the combustion chambers of cylinders #2, #3, #4 and #5 have a crack at that point. Only the combustion chambers of cylinders #1 and #6 doesn’t have them. I assume that the coolant channels are larger at the front-and rear side of the engine.

The red arrow points to a crack that I just discovered during the analyses of the high-resolution version of that picture. Given the fact that Udo specifically mentioned cylinder number six and all the other cylinders don’t have any damage at the same spot, I think that this is the crack that he meant in his phone conservation. But when looking at the detailed pictures, I must admit that all combustion chambers have this damage to a more or lesser extent. Although the high resolution pictures provide some detail, my Sony DSC-F717 is not an adequate tool for doing so. It simply lacks the capabilities to capture microcontrast level such as a DSLR with a decent lense can do. Retaking these pictures, but then with my Nikon D70 and 70-200VR/2.8 lense will provide for much more detail into the microcontrast level, but may be academic. Would be a nice experiment though. It certainly has a usable macro range.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img307a.jpg]

I am playing with the thought of having it send to the machine shop to have it analyzed and pressure tested. This doesn’t break the bank and will achieve objective results. Provided that it tests OK at that point and ALL the cracks can be repaired reliably, why not repair this head, and fit a complete new valve train ?

If that particular crack cannot be repaired reliably to my terms and conditions, then it is off course game over. A new head with a new valve train (option [3]) still is significantly cheaper then a RMFD engine [1], but only if the current engine block can be reused. Off course, I need to budget for bearing replacement etc. I have the feeling that this will end in an investment that comes close or exceeds the cost of a RMFD engine, the worst case scenario.

Camshafts are visual OK and resemble that of what can be expected for a 95k mile engine. The Timing chain, the sprockets, the guides and the oilpump for instance must be replaced, but those don’t determine the cost. The chain guides are worth zooming into though.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img309.jpg]

The chain guide in the head is hardly worn at all. I assume that it has been replaced.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img309a.jpg]

The wear patterns in the lower chain guide (engine block) are much deeper. This probably is the cause of the distance of the OT mark on the vibration damper and the OT mark on the timing chain cover. More importantly, this proves that the lower chain guide has never been replaced and the chain also not.

There is a thread on the German forum in which member JackMoore is documenting the engine rebuild of his S38B36 engine. In particular the following picture triggered my attention.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img310_jackmoore.jpg]

Now, compare that with the picture of above mentioned cylinder head from member Robinson that he bought from a Dutch breaker some years ago.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img299.jpg]

It was sold to him as a usable cylinder head from an S38B36 engine, but notice the difference in the combustion chambers. If that head is indeed from an S38B36, it must have been machined. It is widely known that machining an M88/S38 head is NOT allowed. Since that particular Dutch breaker was focussing on the E34S M5 those days, he must have known about that. It surprises me that Robinsons engine managed to run 40k km with that cylinder head.

These pictures visualize my argument against using a S/H head as has been suggested by some members.

It’s great to have choices. As long as one doesn’t make a decision, it is easy to live with them. They offer a great opportunity to gain knowledge and that is why I love choices. But after a decision has been made, the opportunity to gain a wide knowledge has gone.

I have reached a point where I don’t have the knowledge to make any decisions. The only decision that I can make is between a RMFD engine and a rebuild. For the latter, I need specialist assistance, in this case of a machine shop. But the question of repairing the head is more a metallurgical issue of the used method and for that I lack the specific knowledge. Maybe I can gain some.

In any case, I also have posted a much shorter summary on the Dutch ‘driving-fun’ forum. One of the members that reacted owns an E30 M3 with an S14B23 engine. He also had to remove the cylinder head for some reason and discovered similar cracks between both exhaust ports. He didn’t describe them accurately enough, but quantified a repair (weld) cost between 500 Euro and 600 Euro. He weighed that against the cost of a new head that for his car was in the 1000 to 1100 Euro range. I checked the *** and found this out to be true for the early 200hp version of the S14B23. The later 215hp, 220hp and 238hp versions including the S14B25 (E30 M3 sport evo) require an investment of between 2385 Euro and 2505 Euro ex VAT. Anyhow, he decided that the difference between repairing the cracks and a new head is too small to consider a repair.

He also added that he learnt from various sources that the repair method is critical. Some say that welding can affect the water galleries underneath the welding spots; some others say it can definitely be done provided one does know what he/she is doing.

Then off course there are the metallurgical and temperature issues to consider. Another member pointed me towards the homogeny of the weld and the effect of the repair method to the flatness of the head. This is an important issue since it is not allowed to machine let alone skim the head [1]. When I extrapolate the repair cost of the above-mentioned S14 head with four cracks to my M88 engine with about twenty of those, I anticipate a repair cost of 2k to 2k5 Euro for my cylinder head, but even then, it will be very tricky. Despite my best efforts to see another point of view, I still believe a new RMFD engine is the best way out of this mess. I am not ruling out a new cylinder head and thus keep the short engine, but the difference with a RMFD engine will be very small. At least it saves me from the hassle of rebuilding the engine, which is also worth quite a lot. In the mean time, I have stripped some more parts of the engine. The thermostat house, the radiator and all the coolant water hoses have been removed.

[Blockierte Grafik: http://rwoe.150m.com/tmp/20080301/img311.jpg]

The next step is the removal of the engine-wiring loom so I can restore the connections towards the coolant temperature sender, the coolant temperature sensor and the temperature switch. I am close to the removal of the engine, but that will not happen untill after my holidays.

It has been two months since my last update. The main reason is that I was busy with the extension of my house. Well, I didn't do that much personally as I ousourced most of the work to a contractor but such jobs take time and I was not able to manage two large projects at the same time so the E28S had to wait.

I did make some time for the annual E34S Alps tour ( some teaser pics ) during which I discussed this subject with member Konstantin and Dominik. They revived the idea to maintain matching numbers. This is an important criteria for enthusiast cars, especially since they have a significant value. E28S M5's have seen a 47% value gain in the last year according to the German Classic Data institute that maintains a 'blue book' for classic cars and young timers.

Besides, Konstantin added the argument that the 2year warranty on new engines does not make much sense given the low annual mileage that youngtimers like my E28S are being used.

With other words, the rebuilding option emerged from the deep. However, I need a new cylinder head for that. Whilst dining in Berchtesgaden on Friday the 19th, we tried to find out if a new cylinder head is delivered as a complete assembly, thus including valves and valve springs. If that is the case, a rebuild does make sense financially after all (compared to buying a RMFD engine from BMW that is).

Last Monday, I called my dealer to inform about the availability of M88/3 cylinder heads. I was told that the last known prices was somewhere close to 2k5 Euro ex VAT, but that these are NLA. Complete RMFD M88/3 engines are still on backorder with an unknown delivery time. I asked my dealer to confirm that from BMW AG, but since their network is limited to that the Dutch dealer system, I am doubtfull that I will receive accurate information. I can use my contacts in the German dealer system, but that is something for next week.

In the mean time, I am contemplating the purchase of a used cylinder head and maybe a complete engine. I did track down a used head in Germany last week for an interesting price and when this part turns out to be usefull I may buy it. Usefull means no cracks and that valve guides and seats can be replaced.

New valves, both exhaust and intake, valve springs etc are stocked in Germany so that should not be a problem. Also a piston ring set and pistons are stocked. It's just that the cylinder head itself is a problem.

I received some pictures from the used head that I found in Germany earlier this week. They look promising, but I want a visual inspection on site so I am planning an 800km trip to Germany in the upcomming week. A nice job for the diesel powered A6 workhorse