Knocking noise
 

I just recently purchased a 1989 300SE. There is a visble oil leak that appears to be from the valve cover gasket. I am also experiencing an intermittent knocking or rapping noise that appears to be coming from the right rear of the engine compartment. Right in front of the firewall. Is this noise timing chain related?

Wrong end to be timing chain related. Timing chain noise would typically be cold start noise. A stethoscope should help determine exactly where it's coming from. A valve cover leak is easy to fix, headgasket leak not so easy, could be either.

Thank you for the confirmation about the timing chain. I will try to pinpoint the noise better with a stethoscope like you suggest.

Frank did you discover the problem?? Mine does it periodically also.

I searched and he hasnt posted since 2007, so he may not even have it now or come here anymore.

At any rate, I am wondering if you may be hearing the lifters tapping? I am not sure, but I think I have heard these need to be adjusted eventually. Not sure... my 300SEL dont do that... not yet anyway. ;)

Good luck!

OK thanks.

I think it might be some front end part...dunno. Its not very frequent.:)

Well, these engines are pretty solid... probably nothing major. :)

Good luck!

When it's running (and knocking), remove the rear spark plug wire. If it goes away, you have a bad piston rod.

Are you sure it's knocking, and not clicking or pinging, etc...? Different sounds mean different things.

From where is the knocking coming. From the engine, transmission, or drive train? Does it appear at start up and go away, or is it related to the vehicle in motion.

Hello, my knocking noise, now that I think of it, was kind of a groaning noise and knocking.
It has not reoccurred for some time. My valve guides are worn and therefore my sparkplugs get fouled easily. I don't think the knocking came from the engine.
Sounds do radiaate and bounce off other parts of the car so sometimes it is hard to pinpoint.
Also my noise seemed to occur especially when going up a hil on right turns.
So yes it occurred when the vehicle was in motion.

Thanks !:)