oily mess

[donbmw]

The paper gasket is a carry over from the  older  way the covers were. Before the type  of cover we have now there was cover under the cover. It only needed the paper gasket to keep the oil in. When the outer cover is off you then had the filter cover that held the filter in place and did not a seal when in place. I think the change we have now is due to the models that have an oil cooler.

Don

[Barry]

.....so if, for example, the $2K o-ring sinks inward or gets damaged, the oil will still stay in the engine.  

The oil might stay in the engine but it will just return to the sump instead of being pumped around the lubrication circuit. Without a gasket at that joint an oil leak tells you that the 2000$ O ring is not sealing and you are loosing oil pressure. That's worth knowing so if by chance the gasket is not needed as a spacer then you are actually better off without it.  I suppose BMW might have thought the 2000$ O ring would not always seal 100% and included the gasket for that reason. It wouldn't look good for a new BMW in the showroom to leak oil from that joint even if it was telling you something important.

[raymr]

So folks rely on a seeping cover to detect a bad o-ring. I can think of a few scenarios where I would not want that to happen (ie a long drive where you slowly lose oil until none is left). However I can imagine if you run an engine hard, you would want some other warning besides the oil pressure light. But if the metal cover mates perfectly with the block, it won't leak even if the o-ring fails, so I wouldn't rely on that. IMHO, the true solution is to have a real oil pressure gauge.  

[nhmaf]

The pressure point at which the oil pressure switch closes to indicate a failure has been considered to be anywhere from about 3 PSI to approx 10 PSI.   There are (or were) some switches that would fit in place but which were set for a higher pressure level, but I do not have any part numbers handy.

[Barry]

Didn't someone mention a 15 PSI switch recently ?

I suppose any switch with the correct M12 x 1.5 thread would work. I've seen a few recommendations that VW switches fit so I did a quick search and found this but it's the wrong thread size and the pressure setting might be considered too high as hot idle pressure could drop below 29 psi. I think switches with an M10 thread fitted /5 bikes which will be why it's said to be a substitute for airheads. I don't doubt that there are pressure switches out there with the correct M12 x 1.5 thread and at various pressure settings.  I'll keep looking.

 http://www.hewisclassicspares.co.uk/oil-pressure-switch-audi-seat-volkswagen/


Looks like BMW 3 series (E21) switches will fit but they are the same low pressure setting.

http://www.onlinecarparts.co.uk/car-brands/spare-parts-bmw/3-e21/11/10578/oil-pressure-switch-sender-unit-valve.html