Bad sound from engine.....

[Black99C4]

Hello, new to the forum have been lurking for a little while and found some good info. Now down to the issue at hand, I have 1999 C4 with 118000 miles. I have had the car for a year now and it is my daily and I put about 140 miles round trip a day, which equates to around 20,000 in that year. Except for a couple cv boots and window regulators it has been trouble free. Changed the oil every 5,000 miles checked the filter no metal, sent samples to Blackstone they said everything thing looked good. No smoking, no real oil usage to speak of. After a roughly 200 mile drive parked the car with no issues, but the next day I started the car to move it in the driveway and upon starting it made a loud hollow knocking sound! The sound quietened down considerably after a few seconds but did not totally disappear. I moved the car and shut it off. Had an appointment so had to go (of course thinking about nothing but my car!) I have briefly started it a couple of times since with no trace of the knocking and even a few light revs there is no noise. Getting ready to drain oil and check filter again and do a lab it is coming up on 5,000. Possibly going to drop the sump pan and have a poke around. Sorry for the long and drawn out post but If anybody might have an idea it would be much appreciated! Thanks in advance.

PS. I need my 911 back!

[yelcab1]

Possible causes:

belt idel bearings (3 of them)
chain tensioner L/R
IMS bearing

I would not start it again, until you verify what is causing the noise.

Good luck.