OldBob

I just bought (cheap) a 92 SL2 with 170k miles. The engine has a loud knocking sound.

The frequency of the noise is about half the engine rpm and occasionally misses a beat or two. It doesn't sound like a rod knock. It is a hard metalic sound, like hitting the cam cover with a wrench.

I pulled off the cam cover and everything looks ok.

The noise is still there running the engine with the cover removed.

Checked the compression: 170, 168, 176, 165, engine cold.

The fellow I got it from bought it with the noise in it. He said a mechanic told him it could be a bad crank sensor which was making it fire out of time. It does sound like a real bad detonation.

It is not setting any engine codes as the battery was removed when I got the car. I don't know how long it has to run to set trouble codes.

The oil level is ok.

Any ideas?

onefast94sc2

might be a rod knocking

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1998 sc2 loaded
no mods yet

Ssicarman

Welcome to the Board

How is the tightness of the timing chain? When they are to loose they tend to sound like a diesel engine. If you suspect rod knock pull the plug wires one at a time to see if the noise changes goes away. the timeing chain would be a good suspect.

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A lousy day in Paradise is still a day in Paradise.

OldBob

Well, I changed the crank and knock sensors - no help.

Decided it was time to drop the pan. Found pieces of plastic from the timing chain tensioner guide rails, some slivers of aluminum, and pieces of the black plastic nose piece of the chain tensioner.

I didn't get into the rods yet - will wait and see what things look like under the timing chain cover.

Thanks for your ideas and the welcome.

Bob

OldBob

I decided to look at the rods before tackling the chain cover. #2 rod bearing spun. Phooey!

These little aluminum engines make different kind of noises than I'm used to in a cast iron 350.

Bob