Het verhaal achter de motorrevisie van mijn E28 M5

[raymondw]

The cracks between the valve seats are not uncommon to cylinder heads of the S14/S38 and M88 engine families, but in most of the documented cases, these cracks appear only between the exhaust valve seats. In that respect, the condition of #231’s cylinder head is more serious with cracks between the intake-and exhaust valve-seats and cracks between the exhaust valve-seats and the spark plug holes. I have doubts about the maintenance being carried out by the previous owners before I took over ownership of #231. Already in the spring of 2001, I had to replace two expensive parts that were manually modified for some reason.





Both facts combined led me to believe that the condition of the cylinder head is not necessarily related to the piston to cylinder wall clearance being out of specification. The cause of the cracks between the spark plug holes and the exhaust valve seats may be over tightening of the spark plugs combined with high temperature rises in a short period of time (dT/dt) or with other words, plain abuse by ignoring a proper warm up phase.

With the valve seats affected by these cracks, their stability is lost and valve clearance affected. Even if I had adjusted the valves in between, an engine failure could not be avoided and would have occurred sooner or later. With the removal, disassembly and failure mode analysis, the second phase of this project is almost completed. The third phase, the actual rebuild will formally start next week after I have given the approval to proceed. The third phase will start with determining the usability of the cylinder head. After the visual intake inspection, Thomas Hoop from the ‘Twentse Motoren revisie ‘ gave the preference to using my original cylinder head, as it had not machined before. The overhaul of the cylinder head is a difficult route, but necessary as using the cylinder head ‘as-is’, is not an option and replacement cylinder heads are not available through the BMW dealer network anymore. This is my main worry so my project planning is as follows:

1: Confirm the usability of the cylinder head.
2: Purchasing the parts that have a time-critical impact.
3: Machining and overhauling the cylinder head with new valve guides and valve seats.
4: Machining the engine block.
5: Assembly of the engine with new oversize pistons (93,55mm), matching piston rings, intake-and exhaust valves, new timing chain and associated parts etc.

With step one being confirmed, I placed the order for six new pistons today. My planning of the completion of the third phase by the end of Mai still stands, but this depends on Thomas and Javier’s operational planning. I’ll try to post some updates from time to time.

[raymondw]

Before installing the revived subframe , I had to do something about the surface rust on the front chassis beams. Member 'richardbaxter' brought an American marine product to my attention, which is known as POR15. POR stand for Paint Over Rust and is a primer coating that can be painted over rusted surfaces. It goes to far to describe the differences to other etching coatings in detail; for that I refer to the POR15 website .

Since I wanted to try it out first and don't need a large quantity, I was seeking for a starter kit that contained all the substances. It was available on the US website, but not from the Dutch resellers who prefer to sell the normal containers for way too much money. I couldn't order the kit directly in the States, but was refered to their German distributer, Ronald Hoeseler who offered the starter kit for 18 Euro's which is very reasonable compared to the US$ price. The DHL shipping cost almost outweighed the value of the kit itself, but the kit was delivered in four working days.



The kit contains a bottle with 'marine clean', which is a highly concentrated degreaser that can be dilluted with water up to a 1:10 rato. The second bottle contains 'metal ready' fluid, which leaves an etching layer on the cleaned metal. The metal container contains the POR15 primer coating. It is available in black, silver, grey and transparrant, but since #231 is salmon silver, I ordered the silver primer coating. Two latex gloves, a pencil and an instruction leaflet are included as well.

Since I already cleaned and degreased the affected areas some time ago, I only used the 'marine clean' to remove the last contaminations. I mixed the 'marine clean' with water in a 1:10 ratio. It takes some time to dry, after which the 'metal ready' can be applied.



The last step is the application of the primer coating.



I added three thin layers which is recommended for industrial applications. The curing time is two to five hours. I'll leave it for overnight so that will do.

[raymondw]

The cylinder head has been blasted to remove the debries and get a full insight in the depth of the cracks. Clearly visible is that the crack (indicated by the green arrow) runs deep into the exhaust port. The true extent of these cracks was only reveiled after the blasting process. The other exhaust valve port (yello arrow) has similar damage, although not that bad as the crack is limited to just underneath the valve seat itself. The other exhaust valve ports have similar damage. It was only a matter of time before these extended to the water galeries.



The last step for preparing the cylinder head for the metalurgist (alloy specialist) is the removal of the valve seats. The first one was done in my presence.



With a dremel tool, an incision is cut in the valve seat to relieve the tension so it can be removed.



After the removal of the valve seat, the crack can be seen in its entity. The crack extends from the combustion chamber, alongside the mating surface of the valve seat, well into the exhaust port.



The valve seat from another exhaust port. The purple arrow points to a similar crack of cylinder #2. Also visible is the difference wear inflicted difference in the valve-seats slope. Due to this, the valve seat does not seal off properly and affects valve clearances as well.



The remaining twenty-three valve seats will be removed today after which the cylinder head will be dropped of at the metalurist's. The following picture shows a cylinder head from an Opel/Vauxhall Ecotec engine that suffered similar damage after a mere 150k km on Liquid Petrolium Gas (LPG). The valve seats have been renewed, but need to be machined before installing the valves.

[Casper]

Respect!

[InjectTheVenom]

Dat compressiekaartje ken ik ergens van Goed balen van dat slechte reparatiewerk zeg... altijd leuk als mensen nalatig geweest zijn, ik ben zelf tot nu toe al zo'n 3000 kwijt geweest aan het najagen van diverse dingen en NOG blijven er dingen naar boven komen. Dacht kwa aandrijflijn klaar te zijn en de normale dingen zoals distributieriem en grote beurt te kunnen gaan doen, klapt er ergens iets in de aandrijflijn waar de komende tijd een diagnose van gemaakt moet worden.
Maarja, we gaan vrolijk door en gaan uiteindelijk gewoon genieten van de beloning voor al het harde werk.

[Chris van S.]

Raymond, wat een verslag zeg he... Succes met het verdere werk.

gr Chris

[Auke M535i]

Fraai stukje werk!

[raymondw]

Last thursday evening, I painted the lower front cross member with POR15 to neutralise the corrosion underneath. The primer paint fills the gap between the spotwelded plates rather nice.



I also installed the front subframe earlier this evening. As I have no complaints about #231's handling and the visible inspection of the bushes and control arms reveiled no defects, I decided against replacing the control arms and bushes. I did use new nuts and bolts though.



I also did not replace the pitman arms as there is no need to do so.

[raymondw]

About two weeks ago, a small parcel, containing six pistons, twelve intake valves and twelve exhaust valves arrived at my dealer.



The six boxes with pistons. To reduce the damage risk, I only unpacked one to make some detailed pictures.



The inscriptions on top. With a 93,60mm bore, the piston to cylinder wall clearance will return to 0,05mm (the last 0,005mm is for the honing pattern). Please note the S38 inscription; it appears that BMW does not distint the M88/3 from the S38 anymore. Judging from the date code, these pistons have been manufactured 12 years ago. By the time I enquired about the availability, BMW had an inventory of twenty-three of these pistons; now just 17.



Comparison between one of the new-and one of the old pistons.



The piston crown!



The bill.



One of the intake valves.



One of the exhaust valves.

[Niels]

Dure maar wel erg mooie pakketjes

[Paul]

1400 euro voor standaard zuigers tering... voor minder heb je gewoon gesmeede zuigers van een goed merk, alla JE pistons.. en die zijn wat beter dan de standaard... waarom niet zoiets erin?

[raymondw]

voor minder heb je gewoon gesmeede zuigers van een goed merk, alla JE pistons.. en die zijn wat beter dan de standaard... waarom niet zoiets erin?

Hoi Paul,

Ik ben bekend met merken als JE en Wiseco, maar deze fabrikanten zitten over de grote plas en hebben zuigers voor een M88/3 niet als een standaard product liggen. M.a.w, ze moeten op maat gemaakt worden. (1) Bij de communicatie om de randvoorwaarden duidelijk te rijgen zie ik te grote risicos; (20 bij problemen heb ik te maken met leveringsvoorwaarden gebaseerd op VS recht; (3). Bij plaatsing van de order moet veelal vooraf betaald worden; (4) levertijd is vaak lang; (5) Garantie van het revisiebedrijf wordt een probleem indien de zuigers niet goed zijn.

Eventuele distributors binnen de EU zie ik dit risico ook niet afdekken en als door een kwaliteitsprobleem van een after market leverancier mij de motor weer in de soep loopt heb ik een groot probleem, vooral als ik de keuze daarvoor aan het revisiebedrij op ga leggen om goedkoper uit te zijn. Ik ben bang dat het risico dan volledig bij mij ligt en voor wat betreft de assemblage van de motor wil ik dat niet. .

Verder vindt ik originaliteit een belangrijk gegeven voor een zeldzame auto als een E28 M5. De onderbouwing daarvan is een rode draad in dit gehele project en komt bij elke beslissing weer naar voren.

Raymond

[Casper]

Mooi spul die zuigers en kleppen!

Watvoor werk doe je, dat hier al deze kennis in huis hebt om zo'n speciaal blok te kunnen reviseren?

[Adwo]

Mooi spul die zuigers en kleppen!

Watvoor werk doe je, dat hier al deze kennis in huis hebt om zo'n speciaal blok te kunnen reviseren?

Niets afdoend aan het werk van Raymond, maar een blok is een blok.. De M88
(dat is het type toch?) motor zelf is an sich niets bijzonders.. Dus revisie is dan gewoon standaard..

Groet,

Adwo

[raymondw]

Niets afdoend aan het werk van Raymond, maar een blok is een blok.. De M88
(dat is het type toch?) motor zelf is an sich niets bijzonders.. Dus revisie is dan gewoon standaard.

Adwo,

Helemaal mee eens.

[Adwo]

Niets afdoend aan het werk van Raymond, maar een blok is een blok.. De M88
(dat is het type toch?) motor zelf is an sich niets bijzonders.. Dus revisie is dan gewoon standaard.

Adwo,

Helemaal mee eens.

Dat overkomt me ook niet veel!

[raymondw]

Whilst we are waiting for the cylinder head being returned from the metalurgist, the engine shop started with the engine block. The bores have been enlarged to 93,60mm to obtain a clearance of 0,05mm with the new pistons. In the mean time, the bores have been honed as well.



An important part of a bottom end overhaul is the selection of the bearings. These are available in standard size (60,00mm) and three oversizes (59,75mm, 59,50mm and 59,25mm) in case the crankshaft needs to be machined. As this is not the case with my engine, the recorded measuremets determine the required bearing size.

However, the bearings are avalable in two color codes (red or blue). This is a classification that depends on the production tolerance from crankshaft and crank-case. With other words, a cranshaft is supplied with matching bearings. This is determined by the colored dots on the crankshaft that in this case is red.



Fortunatelly, the colored dots were still visible on this particular crankshaft. If they weren't the BMW repair instructions state that the crank-case determine the required bearings type. In my case, the crank case has red dots as well, thus matching those on the crankshaft.



With other words, the main-bearing selection is unambiguously determined by the crankcase, cranshaft, but also the markings on the old bearings. This is a bit more difficult for the piston rods. As clearly can be seen, these have red color dots as well. However, matching bearings are not available anymore.



Only rod-bearings with the yellow color code can be bought. This is worrying, but I don't have a choice so I have to do with these. Given the fact that the tolerance of these bearings is less then 1/1000 of a millimeter and the recorded journal diameters indicate the clearance ending up within specification, plastigage measurements must provide the empirical proof.

In the mean time, I have ordered all the parts that are needed to finish the short engine block. This includes the gasket sets, sprockets, guides, timing chain, bearings and all the bolts and nuts to complete the short engine. I also am preparing three scientific documents that decribe the failure mode analyses and the rebuild with underlying proof of all the choices that have been made, including the overhaul proces.

[raymondw]

After boring and honing the short-engine in the week before, the machine shop removed the water-channel coverlids and cleaned the engine thoroughly, after which it received a finish with application specific black paint. In the mean time, my dealer received the three separate batches of parts that I ordered for the assembly of the short engine.



To manage this project successfully, I have decided to separate the parts ordering to match the different rebuild stages. This not only gives a better overview of the deliveries, but also reduces the risk of mixing up parts between the few stages. Fortunately, BMW still offers gasket sets for the M88/S38 engine family. Two sets are required; one for the cylinder head and one for the short engine. The gasket set for the short engine is relatively cheap. The stealer wants ~65 Euro ex VAT for it which is a bargain if one considers that both crankshaft seals are included.



Much more expensive is the cylinder head gasket seat that retails for around 320 Euro ex VAT. But it contains all the required gaskets including the cylinder head gasket (120 Euro ex VAT) and the valve stem seals (45 Euro ex VAT).



Clearly visible are the two valve stem seal repair kits. In total the cylinder head gasket contains 62 separate parts. Many of the O-rings have a minimum order quantity (MOQ) when ordered as single parts so the gasket set makes a lot of sense.



The sump has been cleaned and painted in application specific silver paint.



The same applies for the timing chain cover. Clearly visible is the front crankshaft seal.



The new pistons have already been installed on the piston rods awaiting the delivery of the new bearings shells.



All the timing chain related parts will be replaced with new parts. The following picture shows the new crankshaft sprocket for the timing chain and the oil-pump chain.



The following picture shows the rear crankshaft seal. It is mounted in an alloy cover that is bolted to the short engine. The bolts and washer plates are replaced as well.



I ordered a new hub as well. The old one contained a small groove, that could be removed by machining, but who bothers at 75 Euro ex VAT. Actually, this is an obligatory part when performing a full engine-rebuild.



The remaining parts needed for assembly of the short engine have arrived at the dealer today. Monday morning, the engine shop will continue with the assembly of the short engine. The cylinder head has not yet been returned from the metallurgist. The expected delivery time will be three weeks, thus the second week of July. This delay means that I won’t be able to install the engine before my summer holidays at the end of July.

[Niels]

Prachtig verslag Erg mooi om zo'n blok opnieuw opgebouwd te zien worden

[raymondw]

The following picture shows the old and new chain guide-rail (tensioner side). The upper part is the original part, presumably 23-24years old. The lower parts shows the replacement part. Clearly visible are the wear patterns caused by the timing chain.



A close up of the cracks in the rubber lining.



The old crankshaft sprocket (left) with the replacement part (tight). I now see that the hub-side of the old sprocket appears to have some damage, but I am not sure about this as the picture only shows a 2D perspective.



The old parts will be kept for the time being. Clearly visible are the dismissed main crankshaft seal (flywheel side), the old chainguides and the timing chain.



One of the old main-bearing shells with a date code that prooves that they were manufactured before #231 left the assembly line at the Preussenstrasse in 1985. This also prooves that the crankshaft still is the original part (new crank comes with new bearings). This unlike a statement from a BMW representative who doubted that this was the case for this particular car.



Suffice to say that the chain tensioner will be sourced from the S50B32 as is described in this reference article.

[steve smith]

Spannerupgrade op een singlerowduplex ketting zou ik NIET doen tenzij je heel erg zeker weet dat de totale belasting niet vergroot. Op de latere dual row ben ik volledig met je eens dat het een must-have is.......

[raymondw]

Steve,

Goed punt i.d.d; ik zal de berekening opzoeken waaraan ik een paar jaar geleden aan heb meegewerkt op de mailinglist en dit punt opnieuw bekijken. Als ik niet 100% zeker ben zal ik alsnog de standaard spanner bestellen.

[raymondw]

With the arrival of the last missisng parts such as the rod bearing shells, the short engine is now in the middle of the reassembly phase. The six pistons and rods have been installed as can be seen on the following picture.



Last week, Ronals used the old crankcase bolts, but with the arrival of the new parts he could complete that part yesterday as well. I am not that keep on the black paint on the pipe for the dipstick, but since I want to replace that part as well, I don't care.



The number of replaced parts increases slowly but steadily.



By advise of member Stevie, I asked Ronald to soak the new chains in a bucket with oil for a week or two. This will allow oil to creep alongside the pins between the shackles for proper lubrication. This will significantly reduce the start-up wear. If all goes well, TMR can complete the short engine assembly soon after.

[raymondw]

In post #275 of this thread, I shared a theory about the engine of #231 being repaired before for some reason. Whilst I was doing some research in the past few weeks, I discovered that the early E28 M5 and E24 M635CSI's were originally assembled with single valve springs that have an realistic chance of failing. This design problem is discussed in detail in a seperate thread about the M88 valve spring risk. When I removed the cylinder head, I found out that the valve springs are of the double spring design so this issue has been addressed on #231 a long time ago.

Furthermore, I have found the conclusive proof that the 93,45mm bore diameter has been determined during the production process. The proof is a '00' inscription in the top-side off the short-engine. This matches the same coding that the TIS uses for an intermediate bore size. The measurements report from TMR confirms this as well.

With other words, the bore-wear is limited to 30um max that is the result of 155k km. Extrapolated to the max pistin to cylinder wall clearance, this means that the short engine could have lasted 510k km before needing a rebuild. However, the piston to cylinder wall clearance has exceeded the maximum value. This simply contradicts so there has to be another explanation.

It is my theory that #231 suffered from a failing valve spring in the first year(s) of its life and that this failure caused one or more valves that dropped and damaged the pistons. In the repair that followed, it is likely that the mechanic missed (or was not aware) of the '00' code on the short engine and just ordered the standard piston set (for size '0'). TMR's measurement report supports this; all pistons measured 93,35mm (max), matching the requirements for size '0' and not '00' that requires pistons with a diameter of 93,40mm.

This proof is only conclusive if I can find markings on the old pistons that proof this. Unfortunatelly, the piston ident cannot be found on the piston-crown. Instead, the piston ident can be found on its top side, however this is coverd by carbon deposits. I removed these and found M88/3 and 10,5 texts. However, I did not find the full text that refers to the piston diameter, but only the last two digits on teh spot were I expected them. Since these clearly reads 35 (and not 40) I have to assume that TMR's measurements re correct.

[GTRene]

man man, das een heel ander karwei dan die kleine klusjes die ik doe mooi hoor al die gegevens en tijd nemend...ik zou de helft elke keer weer moeten opzoeken pfff en al die aantrek koppels hm...nee niet zoveel behoefte aan
vroeger reviseerde ik wel eens zündapp blokjes of puch en Yamaha blokjes ook wel gedaan maar een autoblock dat moet wel heel goed gebeuren en der zit wat meer op en groot/zwaar