Introduction:
Last weak, I had another brain wave about the failure of my M88/3 engine and found evidence that the (0,05mm) larger bore has already been determined during the production process. This contradicted to my first theory about the bore wear that simply is too large for an engine with just 155k km. That subject is beyond the scope of this article, so I won’t go into detail, but whilst researching the archives on two E28 specific forums with mainly US members, I read reports about valve spring failures in the M88/3 engine. As I was unaware of this subject, I searched a bit deeper into the archives and read about a service bulletin about this subject (SI bulletin 11 12 86).
Afftected cars:
Since BMW already addressed this problem in 1986, it is likely that only the cars that were manufactured before 1987 were affected. This rules out the bulk of the E28 M5 and E24 M635CSI's, but early UK and SA cars may be affected as well.
Cars manufactured before 1986 are affected. Thus including the ECE LHD E28 M5, ECE LHD E24 M635CSI and SA RHD E23 745i.
Problem:
Originally, the M88/3 valve train design featured a single valve-spring that was not really robust. BMW addressed this problem already around 1986 with a redesign featuring the double valve spring design that we also can find in the S38B35, S38B36 and S38B38 engines. Although this is a long time ago, reports about this subject are rare. However, since many M88/3 powered cars found their way into the US as grey-market imports, BMW NA did not accept liability for this issue, leaving this problem to the owners-and distributors of these cars. This means that many M88/3 powered cars in the US did not receive the double valve spring upgrade. Some did, many did not. On the dedicated forums and mailing lists with active US owners, reports can be found of failing valve springs in the M88/3 engine.
In Europe however, it is assumed that most cars received the upgrade either as a recall or as an upgrade during scheduled service. In my M88/3 engine, the valve-spring upgrade has been carried out.
Risk:
The risk with the single valve spring is that when it breaks, a valve will drop with a significant risk to severe engine damage.
How to check:
Given the fact that this issue has been addressed a long time ago, it will be difficult to find evidence that the upgrade has been carried out in the past. The only way to check weather or not this upgrade has been carried out is by removing the camshaft housing for a visual inspection of the valve-springs. The cylinder head itself does not have to be removed.
Upgrade:
Service bulletin 11 12 86 describes the valve spring replacement procedure without removing the head. The required parts can be found in the parts catalogue from the manufacturer or REALOEM.
Difficulty level:
Inspection and replacement of the valve-springs is a specialist job and beyond the capabilities of most DIY-individuals. Therefore, consult with a reputed specialist before addressing this issue.
References:
[1]: M88/3 Spring Failure Analysis by Chris Richards: published on the s38m88 mailing list (yahoogroups) in January 2003, message #588.
[2]: TIS document 11 12 86
Linear Mode
