Unofficialbmw.com

[jag956]

every time i start my 318i (1990 model) i get a wierd knocking sound for a few seconds. Then when i start driving it vanishes...BUT whenever i drive over small bumps i can still here it. The steering is fine the drive is still perfect. Any ideas what it might be??

[rduckwor]

If your car has the M42 twin cam motor, get the timing chain tensioner checked this week. This motor has some history of wearing the tensioner out and you may be hearing the chaing rattling on start up. The fact that you hear this when you hit a bump may well indicate that the tensioner is not holding pressure against the chain very well. Shouldn't be a big hit to the wallet, UNLESS the chain jumps a tooth or breaks while loose. Then see your loan officer. Pay a little now or a lot later basically.

HTH,

Bob Duckworth

[gamma]

sounds to me more like you have a loose heatsheild on your CAT, or possibly a rotten + broken exhaust to gearbox clamp.

[wrbowen]

My 91 318is had the cam chain tensioner problem. It goes away when the engine heats up - dealer repair $175.00. I suspect exhaust problems - clamp or more likely cat converter.