Het verhaal achter de motorrevisie van mijn E28 M5

[raymondw]

I have started making preparations to lift the engine block. First, I removed the exhaust headers to gain some clearance.



These headers are a nice piece of art. Safely stored away.



Tapping of the old fluids (in this case the less then 1500km old Castrol TWS 10W60.



Next step is the removal of some heat shields and the remaining auxiliary parts.

[raymondw]

Some would argue that it didn’t make sense for a 378km single distance trip to inspect a cylinder head with an asking price that is lower then the net-cost of the trip. If I would have to use my E34S M5 that would certainly have been the case, but I didn’t want to risk the chance that the cylinder head is nothing more then scrap metal. The seller (Andreas Heuer, owner of ‘E28 power’) did send me a few digital still images, but their resolution and quality were too low to make a decision so I took the plunge and decided to inspect it on site. We used my fathers Audi A6 2.5TDI for this trip, saving a few pennies on petrol cost. As I wrote in a previous post, I didn’t buy the cylinder head directly as it did show some faults and I wanted an expert opinion about two of the artifacts. Andreas did describe the artifacts on the phone beforehand, so they didn’t come as a surprise. Let’s zoom in onto two of the defects.



The red arrow points to a groove around the intake side of the combustion chamber for cylinder number three. The green arrow points to bubbles in the casting. It is unknown weather these are caused by the casting process or by another phenomenon.

This groove itself has a depth of roughly one millimeter. This is too much for machining down the cylinder had as there is no oversized head gasket available because of the unique construction of the valve train due to which it is impossible to re-torque the head bolts once the engine is assembled. To allow such a construction, the head gasket is made from high-grade steel [1], hence why it costs so much more then the normal head gasket of the SOHC M90 engine (E12 ///M535i) that uses the same engine block as the M88/3 engine.

The most plausible explanation for this groove is coolant that escapes through a leakage path between the cylinder head and the cylinder head gasket where it changes into a gaseous state and explodes under high temperature. The bubbles (green arrow) could be the result of the casting process during production. According to the machine shop, both faults can be restored by routing out the damaged spots, fill them with new alloy and skim it to specs.

This cylinder head does not suffer from the cracks between the intake-and exhaust ports as is the case with so many M88 / S38 heads. But if one takes a closer look on the following picture, a small hairline crack can be seen between the exhaust valve-seats (purple arrow).



Normally, such a small hairline crack is nothing to worry about, but not to my requirements. Although I still prefer a new cylinder head, BMW’s policy to declare the M88/3 heads as no longer available forces me to rely on craftsmanship instead of process control. Maybe (and I hope) they will change that policy in the future. If the BMW Classic department (formerly Mobile Tradition) want to reach the same level as the Classic center from ‘Das Haus’ they have to reconsider their policy. Nuff said.

Based on above pictures, the machine shop that I will use for overhauling the engine thinks that the cylinder head in Schöningen is usable so I agreed to buy it. A week later, the parcel with the cylinder head was delivered on my doorstep and after a visual inspection moved to my workshop where it resides in the same rack that I use for storing engine parts on.



In any case, both cylinder heads need a significant amount of work and if I will use the cylinder head that I bought from Andreas, I assume that I need an oversized head gasket as well. According to member Stevie, these can be custom made from a third source. Another option is to use the solution that member jrobbo used when he had to rebuild the engine of his E34S ///M5 in 1999 [2]. He used a laser cut steel shim as compensation for the machining losses to straighten the cylinder head in combination with an OEM head gasket.

To make this project work, I will need short lines to the machine shop, hence why I have decided to do business with one in my near vicinity. When some engineering decisions need to be made, I can convince myself without the need for long distance traveling.

References:

[1:] M88 engine description by BMW Motorsport Gmbh (page 5)

[2:] Engine rebuild description written by member jrobbo as published on the M5 springboard and later on the [url=http:bmwe34m5.com]E34 M5 FAQ’s[/url].

[raymondw]

I proceeded with the removal of ancillary parts last Monday evening to prepare the short engine block for lifting. The cranckshaft sensor came off rather easy, but my attention was put to the patch close to the connector.



I removed the insulation tape to inspect the wiring. The two signal wires and the shielding braid have been damaged in the past and very poorly repaired. I will have to replace this sensor with a new one at a cost of over 200 Euro's for the part alone.



[FONT=Times New Roman]The alternator is the next part that came of.[/FONT]

[FONT=Times New Roman][/FONT]

To avoid further damage to the DME wiring loom, I removed it fully. This will allow me to inspect it more closely and repair the poorly repaired patches that have been described in this thread earlier.



I have to disconnect the oil lines from the oil filter house, but when that is done and the engine is unbolted from the gearbox and the engine mounts, the engine is ready to be lifted.

[raymondw]

It doesn’t make much sense to buy an engine-crane just for this occasion, so I borrowed one. The downside is that I had to wait for it becomming available. We first gave it a try on Wednesday evening 3-December.

With most of the preparations done, we ‘only’ had to unbolt the gearbox und engine mounts. I had a distinct preference for keeping the gearbox in place. It is bolted to the engine with eleven bolts of different lengths and sizes, but all of them require a so-called inverse TORX nut. Stahlwille, a German tool manufacturer, offers these in a few sizes as special tooling for BMW.

I don’t really know how it is possible to remove the gearbox without removing the engine, as four of the bolts are almost impossible to reach. Maybe there is a special tool or the engine needs to be lowered, but even so, three of the upper bolts have to be removed without seeing them. Better make sure you have the right high quality tools for that and don’t over torque these bolts as you’ll regret it when having to remove the gearbox again.

I suspect that this was my problem, as I doubt that #231 still has the original clutch after 23 years, but that can be investigated later on. With little space to work, removing these bolts is a serious challenge, even with the cylinder head out of the car. The following picture shows two of the upper bolts that were really tight. We managed to unbolt the right bolt on Wednesday evening, but no such luck for the more accessible bolt on the left.



This bolt can be seen from underneath the car and with some halve inch extension tools it can be reached, but even with the right nut, it didn’t turn. By that time, it was already 11:00PM so we called it a day and my acquaintance who helped me with this stage thought he had access to suitable tooling. We agreed to give it another try again on Thursday evening Wednesday the fourth but something came up in between so we postponed it to last evening (8 December).

My acquaintance brought a few nuts that have the distinct function of finding grip in damaged heads. I don’t know how these are called, but these nuts have a few sharp blades that penetrate the bolt surface in perpendicular direction to allow a fair amount of force to be applied without loosing grip to the head. Fortunately, my halve inch ratchet has a very small pitch, which came in very handy in the crowded working space. It didn’t take much time before the troublesome bolt came off.



I don’t want to reuse the bolts anyway so I don’t care. With nine bolts removed and no other bolts in sight, it was time to position the engine-crane and attach the chain to the lugs on the engine block. But the engine didn’t move forward. Also disengaging the clutch didn’t help. We then removed the starter-engine and the alloy engine mount on the exhaust side to get some more clearance when we discovered two more bolts sitting in the way. Problem was that these are even more difficult to access. Blunt said, there is no room to put on a halve inch nut. We tried of course, but to no avail. I finally decided to remove the engine and gearbox together, so we unbolted the gearbox support, removed the slave cylinder, gearshift, disconnected the propeller shaft and some wiring. Before reattempting to lift the engine, we first installed some of the bolts between the gearbox and engine to prevent the remaining bolts being overstressed.

This time, everything worked like a charm and the gearbox/ engine assembly was ready to be lifted.



Even though the radiator had been removed, the clearance is very tight (less then halve a centimeter). I needed to place the hood in a close to vertical position to gain enough clearance for the engine to be raised high enough for the gearbox to be maneuvered over the front nose but other then being hard work that was not really difficult.



Before calling it a day, we separated the gearbox from the engine. The two remaining bolts were very tight and could only be released with air-powered tools. With other words, the gearbox had to come of anyhow.



I have to strip the engine a bit further to prepare it for shipment to the machine shop. But with most of the removal work being done, I can focus myself on restoring functionality.

[raymondw]

I have stripped the engine block from all the removable parts.



The pulleys and the harmonic balancer are for the machineshop as I don't have a breakerbar for the 36mm hub nut. Also not advisable with the engine hanging on the crane. The only other part that I could not remove is the bracket for the A/C pump because two of the 13mm bolts are only accessable after removing the harmonic balancer.

We removed the clutch shortly after seperating the engine and gearbox.



The gearbox with the release bearing. Looks rather messy. It appears that the seal of the prise-shaft is leaking. I think that most cars suffer from this.



Damn, what do I hate this. A dealer replaced waterpump with less then 3k km on it. This should not have happened if the cooling system has been run on low mineral coolant (glycol). Just replacing the waterpump and topping up the coolant clearly is not enough. Looks crap to me.



With the engine out of the car and the wheels a few inches higher there is much more work to do some simple work of cleaning up the engine bay and do so cosmetic work.

[Michel P]

Mooi leesvoer voor de kerstdagen.

Succes met de rebuild.

Michel

[MartijnGizmo]

Net alles gelezen, vind het persoonlijk altijd heerlijk om van die uitgebreide verslagen te lezen...

[Hans]

Mooi verslag.

[Bert ///M3]

Leuk topic.

Valt mij op dat een hoop motordelen er nog heel goed uit zien na zoveel jaar

[G Kolkman]

Leuk topic, zie bekende onderdelen voorbij komen ! Zo'n E28 ziet er qua engine bay echt vergelijkbaar uit met een E30. Ik mag je grondinge en georganiseerde werkwijze wel. Helaas vergt deze wel veel ruimte, maar je hebt er bij het terugbouwen véél gemak van.

That said: wees súper voorzichtig met het vervangen van de seals van de bak. Je hebt het metaal in no-time beschadigd .

[Marc R]

RESPECT KEREL!


Veel succes met je rebuild......gaat helemaal goedkomen denk ik.

[HSR]

Prachtige Rebuild!

Als ik tzt weer in Twente ben zou ik de wagens wel eens willen bezichtigen.

[G Kolkman]

Minimeet !

[steve smith]

Maestro, je bent nog een bewerkt fototje vergeten te kopieeren uit die andere draad

[raymondw]

I received a small update from the engine rebuilder who just started working on the engine by taking it apart and measuring the bearings, cranckshaft, pistins etc.

I have to wait untill Monday before I can take detailed pictures, but he informed me that the cranckshaft and bearings are OK, but the clearance between the pistons and cylinders is between 0,12mm and 0,16mm. According to him this is twice as much as regular.

I did call my dealer for factory specifications, but they have no such data for the M88 engine, only for the S38 that apart from the B38 engine has the same bore. The chief-mechanic send me the data by fax so will compare them with the obtained results before drawing conclusions.

According to the engine rebuilder, the measured wear is twice as much as what is normally accepted. He suggests going oversize and use new oversize pistons.

[raymondw]

I had the subframe bead-blasted and powdercoated. Looks much better then before.

[raymondw]

The TIS specs for the S38B35 are:

Bore: 93,40mm (+0,01/-0,00)
Bore-midsize: 93,45mm (+0,01/-0,00)
First oversize: 93,60mm (+0,01/-0,00)
First oversize: 93,80mm (+0,01/-0,00)
Surface roughness: 0,2 ... 0,4 (Ra [mu])
Max allowable ovality: +0,005/-0,005 (mm)
Max allowable conicity: +0,01 (mm)

[raymondw]

Whilst on my way to work this morning, I made a small detour to see the fully disassembled engine from my M88/3 which was carried out by member Javier who coincidentally works for the engine shop that we selected to carry out that work.



The engine block in disassembled state.



The six pistons.



The internal parts layed out on a table.



Just a randomely selected cylinder (this case #6). clearly visible is the machining pattern (grooves). Clearly visible is [d1] The brown tinted surface on top of the cylinder and [d2] the cleaner looking surface from the bottom up until one third of the height. The surface in between [d3] is used by the piston-springs and wear out over time. With other words, there diameter of the bore that is 'used' by the piston springs wears out in time and with heavily worn engines, a ridge can be felt on the cross-over points between these surfaces that may prevent the removal of the piston without damaging the cylinder walls. If that is the case, the cylinder needs to be bored anyway so that doesn't matter. Javier did make a report with measurements that he carried out to determine the wear of the engine.

Javier was not present this morning so I had to do with the measurements for [d3] that he wrote down.

cyl #1 [d3] = 93,48mm
cyl #2 [d3] = 93,47mm
cyl #3 [d3] = 93,47mm
cyl #4 [d3] = 93,48mm
cyl #5 [d3] = 93,48mm
cyl #6 [d3] = 93,48mm

I discussed these results with his collegue and additionally measured [d2] that turned out to be 93,45mm for all six cylinders. The bore wear is determined by substracting [d3]-[d2] or 20umtr to 30umtr for all six cylinders. The original diameter is what is strange. According to the BMW specifications this must be 93,40mm ('size 0'). Coincidentally, 93,45mm matches the so called 'size 00' in the technical information. Above 'size 00', there is 'size 1' and 'size 2'. Both are oversize (93,60mm resp 93,80mm). Unknown to me is were 'size 00' is used for but it does list a matching piston sized 93,40mm.

The pistons in my engine measured.

piston #1 [d] = 93,35mm
piston #2 [d] = 93,33mm
piston #3 [d] = 93,31mm
piston #4 [d] = 93,32mm
piston #5 [d] = 93,32mm
piston #6 [d] = 93,35mm

There are no inscriptions anymore what the original construction size is, but I assume it is 93,35mm, the matching piston for 'size 0' since for 93,40mm the wear must be visible on the piston. So someone must have decided in the past to machine the bore according to 'size 00' whilst using the pistons for 'size 0'. This equates to 50umtr or 30% of the allowed piston-to cylinder wall clearance (0,15mm) !! I have no clue who is responsible, but it sure is strange. Sounds like some cost cutting measures by a dealer who had a warranty claim (or something like that).



A randomely selected main bearing journal on the cranckshaft. Their diameter measured 59,97mm for all but one that measured 59,98mm.



A few (lower) main bearings still in the main bearing caps. After 155k km these still look excellent.



Some other (upper) main-bearings. Also these are still excellent.



A randomely chosen piston rod with the rod-bearings still installed. Also these bearings didn't show a sign of wear. Their journals on the cranckshaft measured 47,98mm for all six.



One of the chain guides. Well worn and thus in need for replacement.



The timing chain sprocket on the cranckshaft. The tooths are a bit too sharp so also these will be replaced.

[steve smith]

Goed bezig Ray!

[raymondw]

The disassembly and analysis of my M88/3 engine is almost complete, so it is time to draw some conclusions. The facts at a glance:

1: The valve clearances for all intake-and exhaust valves were to small.
2: The cylinder head gasket has S38 printed on the topside.
3: The engine wiring loom has been damaged on two spots.
4: The original bore diameter of all six cylinders is 93,45mm, matching ‘size 00’
5: The pistons in diameter are close to the value for ’size 0’

Facts 4 and 5 combined led me to believe that the engine needed serious repairs at some stage in the cars life. Normally, if an engine needs to be bored, a matching set of pistons must be used as otherwise a significant part of the engine-life is wasted. From the factory, BMW manufactured the M88 and S38 engine with a 0,05mm clearance between cylinder wall and pistons. As maximum clearance BMW specifies 0,15mm for a worn engine. This has not so much to do with oil consumption, but more with the maximum tilt of the pistons during cold start.

I rule out excessive piston wear, as these are not designed to come in contact with the cylinder wall. There are no (visible) signs of scoring either, so I can safely conclude that the pistons are originally 93,35mm in diameter, matching the criteria of ‘size 0’ in the TIS. The difference in measurement recordings can be explained by measurement tolerances and metal expansion / retraction due to temperature cycles.

The main question is: What caused the 93,45mm bore size what should have been 93,40mm? The difference seems to be minor, but bare in mind that the maximum specified piston-to cylinder wall clearance is 0,15mm. Subtract the initial manufacturing clearance of 0,05mm (the tolerances are ignored for simplicity) results in a mere 0,1mm as maximum wear. As a rule of thumb, one can assume that an M88/S38 engine lasts 300k to 350k km before needing a rebuild (abuse excluded). With these figures, the slope of the engine wear can be determined to a value between 0.00000029 and 0.00000033 mm/km.

Compared to the original bore size, the cylinder wall wear on my engine is determined at 0,03mm. Combined with the very good condition, i.e. minimal wear on crankshaft, bearings, camshafts, the true life of my M88/3 engine can be assessed to between 91k km and 104k km. Granted, this is an educated guess, but I can safely assume that this is within a ten percent accuracy, setting the limits to 82k and 115k km. However, the mileage indicator on #231 shows 155k km, meaning that the engine must have been opened once before. Corrected for the calculated true life, this must have occurred between 40000km and 73000km. Chances are that the factory warranty had already expired and that #231 was still in the hands of the first or second owner and the repair was covered under goodwill or a used car warranty. In that case, it was the seller’s responsibility, most likely a main dealer.

The logic is that if the pistons are original, they measure 93,35mm nominal. By increasing the bore to ‘size 00’, the piston to cylinder wall increases to 0,10mm! Although still within limits (0,15mm max), roughly halve of the engines operating life expectancy is wasted, meaning the engine wear reflects that of an engine with 150k to 175k km. A dealer would call this a successful repair with the problem shifted outside their liability or possibly outside the cars technical and economical life. The customer would not notice that the trade-off in engine life is at least 77000km just to save on a new piston set!

One may argue that this occurred at the factory already in 1985, but I think that is unlikely for a variety of reasons. First, if this engine block has been rejected initially due to a tolerance issue, it is very unlikely that the engineers would have enlarged the bore to ‘size00’ without using a matching piston set. Second, the engine wiring loom has been damaged and this would not have occurred at the factory. Lastly, the cylinder head gasket that came out of this engine has S38 printed onto it. This designation did not exist at the time #231 was manufactured in October 1985, let alone the manufacturing date of the various single parts some of them being stocked months before.

[Robert Campbell]

Dus met andere woorden: Hij is uit mekaar geweest en slecht gerepareerd. Wat ga je nu doen?

Rob

[Niels]

Tegenvaller dus Gaat een hoop geld kosten om het naar de zin krijgen maar goed, kost zowieso al genoeg

[raymondw]

Tegenvaller dus Gaat een hoop geld kosten om het naar de zin krijgen maar goed, kost zowieso al genoeg

Hoi Niels,

Ik hield er stilletjes al een beetje rekening mee dat uit het onderblok nog een verborgen gebrek kwam. Op zich vallen de exta kosten wel mee, t.w zes nieuwe zuigers met wat machine-uren. Het extra werk zal met 1700-2000 Euro te begroten zijn. In zijn geheel kom ik dan op 6700-7200 Euro ex BTW. Is nog steeds 1300 Euro minder dan een nieuw AT blok. Economisch gezien kan je je afvragen of het zin heeft te reviseren, maar ik wil graag 'matching numbers' houden.

De technische keuze is beperkt. De kosten zitten in zes nieuwe zuigers, dus het heeft geen zin om op de boring-tussenmaat te blijven zitten. Via Mahle direct is de tweede overmaat verkrijgbaar (+0,4mm). Bij BMW kan ik ook de eerste overmaat krijgen (+0,2mm). Prijstechnisch is er geen groot verschil tussen beide opties. Ik neig zelf naar de eerste overmaat (+0,2mm) omdat het dan nog steeds mogelijk is om naar de tweede overmaat te gaan (+0,4mm). Ga ik in een keer naar de tweede overmaat (+0,4mm) is verder opboren onmogelijk en zit je aan cyl bussen. Maar goed, daar zal ik bij de E28 als alles goed gaat nooit meer wat mee te maken krijgen.

Er is nog een andere mogelijkheid; Niets doen aan het onderblok. Dan blijf ik op een zuigerspeling van iets meer dan 0,16mm zitten. Het blok zal er niet van stuklopen, maar het risico op kantelende zuigers gaat toenemen. Is m.i geen echte optie, maar ik sta open voor argumenten.

[Niels]

Tja een uitvoerige deelrevisie voor 5K of een volledige voor 7K dan wist ik het ook wel weer. Natuurlijk veel geld maar dat is 5K ook Ik zou er absoluut nieuwe zuigers in willen hebben in jouw geval. Een vriend van me heeft ooit een kantelende zuiger gehad en op zich waren de kosten voor het materiaal niet dramatisch maar de schade viel in zijn geval ook mee(honen, nieuwe zuiger) maar vergeet niet dat het allemaal weer los moet en er ook nog weer een pakkingset bij komt. Daarnaast valt niet te leven met een inverstering van 5K met de wetenschap dat het niet 100% is. Dan geniet je er nog niet van Die auto wordt alleen maar meer waard. Misschien nu niet meteen de inverstering maar met de jaren schrijft ie toch niet af, integendeel! Matching numbers zou voor mij ook een pre zijn

[raymondw]

This evening, I started with one of my secundary goals that is so easy with the engine out of the car. When I removed the subframe, the mating surface of the chassis-beams were a bit corroded. Just some 'fly-rust' and nothing serious, but something that needs attention.



With some light sanding, I could remove the corrosion and the old primer coat.



More serious are some welds deep in the engine compartment. A dremel came in handy and allowed me to remove the rust between the sheet metal plates on the borrom of the following image. The weld right next to it was attacked by corrosion as well, but nothing serious.



P.S: The bracket for the AC condensor will be replaced.