Knocking sound from low-mileage Cayman (with clip!) - professionals are stumped
 

Hey All,

I'm experiencing a vexing issue on my 2006 Cayman S with just 7300 miles on the odometer.

It's making this sound

The sound started right after I changed the oil (5W-40 - same weight and brand what was in the car before: Pennzoil Ultra Euro). I filled the car with 8 quarts of oil (usually enough to get the oil level gauge to one of the middle bars) and started the car. I got a very brief "oil pressure low" or similar warning on the dash readout which went away in a second or less. I assume that it simply took a moment for the oiling system to purge the air from it. I let it idle then topped off the oil.

Shortly after I noticed the sound. At least I think so, I do not recall the sound before changing the oil.

I attempted to diagnose the problem myself to no avail, and brought it to an independent Porsche specialist for inspection. They replaced the oil pump pressure relief piston (a known issue and TSB) but that failed to fix the problem. They have been unable to definitely determine the issue, but noted that using a 0W-30 weight oil drastically reduces the noise. This corroborates with my observation that with 5W-40 the noise worsens as the engine and oil warm up.

I'm inclined to think that it's a sticky lifter as oil thickness/temperature correlates with noise, but it seems too intermittent to be a fully stuck lifter. The shop recommends driving it gently on 0W-30 for a while to see if the problem goes away.

Any direction is much appreciated!

Bump hoping to get some insight!

Seems to be fairly loud... Does it go away above a certain RPM?

The clanging sound got faster with higher RPM, but it was not 1:1 as the sound was still intermittent.

Follow-up:

I picked up the car yesterday. The clanging is gone. I brought the car to a second reputable Houston Porsche shop and let them have a listen. They couldn't hear anything amiss at all.

As mentioned, all the first shop did to "fix" it is replace the 8.2 quarts of brand new, Pennzoil Ultra Euro 5W-40 ($$$) with 0W-30 synthetic and drove it. The owner of the shop thinks that something went amiss during my oil change; perhaps dislodging a carbon deposit that the 30 weight was able to address. He admitted it's completely speculative and didn't like the answer, especially for a car with such few miles, but short of tearing the engine apart that was his best guess.

The shop owner suggests driving it as is for 1K-2K miles and then going back to a 5W-40. Provided it is not tracked (it won't be), the 0W-30 will be fine in his opinion. For peace of mine, I'll do a UOA on the 0W-30 as well.

I'm happy to have it healthy and back at home

0-30! reputable!

no dice.

One's reputation and their opinion are two different things. That the shop is refutable is irrefutable. That 0W-30 is a means to a fix is debatable.

I don't love the idea of a 0W-30 "cleaning batch" either.

yeah, i stopped reading after "with 0W-30 synthetic and drove it" and didn't see the whole 1k-2k then switch back. so i withdraw my comment.

i don't know how an oil change could produce the noise, but who knows. if it's gone then "something" fixed it.

as an aside, i had a noise that i could not figure out for a while, thought it was a heat shield but turned out to be a loose alternator. the shop i use (which i consider reputable) was all ready to cut off the heat shields. i found out it was the alternator on my own...

Don't let anyone talk you into cutting shields. They are there for a reason...your CV boots will thank you.