while changing the oil and filter on the SIII, I noted that in the bottom of the oil filter housing was a spring. The only purpose I could see for this is to press the filter element up against the mating flange at the top, and indeed without something to do that, the oil can bypass the filter altogether. However, for the spring to do that, there has to be a bit which wasn't there, like a large flat washer, to fit over the bolt, between the spring and the filter. I improvised it using a large washer from a damper bush which happened to be lying around and was approximately the right size.
Anyone know what should be there, and whether you can get 'em? 'Twould be nice sometime to put it right.