Posted by Lars PNW 81_528i on June 30, 2001 at 13:17:02:
In Reply to: Valve Stem Seals - quick question posted by Bob N. on June 30, 2001 at 10:44:07:
Valve stem seals wear for two reasons.
1) Quality of the seal in the first place, plus keeping oil levels up and all galleys tight, such as oil spray bar, etc. I have been told a number of times the seals in early fives is not as good as the later models.
2) Wear in the valve guides themselves, which allow lateral movement of the stems, contributing to seal wear.
The consequence of those two factors add up to the fact that if you do just a stem seal replacement, your seals will wear out faster than the first go-round. Hence, the reason so many old bimmers puff a cloud of blue-grey smoke on startup. It's just not time for a full valve job complete with new valve guides yet. Plus, the fact that oil is still cheaper than a valve job... at least today.