Quote:
Originally Posted by Jake Raby
This is the most common issue with the M96.21, M96.22 and M96.24 engines. These are all Boxster power plants. I see 15-20 per year.
Typically the bank 1 intake cam and lifters fail, 65% of the time its the #1 cylinder, outboard intake valve that fails first.
Approach repair with care. Collateral damage from this failure can bite you later, especially considering he debris levels in the oil, and the chances for a bent valve/ broken valve spring on the effected position.
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That is all info that I have read from other posts and techs. I was hoping someone may have some info as to
why it happens. Bad version of lifters? Poor oil supply to those lifters? Soft cam lobes? I know that the local shops just replace lifters when this happens. Given that it sounds like it usually happens with lifters at the same location consistently, it sounds like perhaps there is an oil feed issue. The odd thing is that that lifter is right under where the oil pressure sender is.
The car was not missing with the lifter noise, and it was running fine the last time I ran. My original theory of why I had that noise was that when the engine stops, it settles with some of the valves open and therefore lifters depressed. After sitting that way long enough with zero oil pressure, they collapse as bit until it is run again and pump up once oil pressure comes back.
I highly doubt that there was any major failure resulting in debris, but I guess anything is possible. I did have a Blackstone oil analysis last oil change and everything looked fine and it had the usual cold start lifter noise then as well. I have had these type of lifters (perhaps even the same ones on Audis) "get weak" on me before with noise at cold idle and maybe after a very high RPM event, but I have never seen one that get this noisy.