Good questions --

Mine started doing this at about 100,000 miles -- or at least that's when I noticed it. If it had done it while under warranty, I would have had the dealer fix it.

Don't know for sure about the ease of doing this. On other cars I've worked on, taking off the valve body wasn't too hard, though you have to be very careful to keep everything exceptionally clean.

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Steve
'93 400E