I have a strange knocking sound coming from a friend's 89 240. I made a sound clip of it, but it's pretty bad on detail. You can hear the knocking, and it sounds like the knocking is coming right out of the intake manifold. The car runs perfect, no codes, no bad performance, etc. Strange. Take a listen, see what you think.
It is a VERY loud knocking. Sounds like a hammer hitting the top of the intake manifold.

Click Here For the Sound File

The knock accelerates and decelerates with the engine rpm's. It gets louder with rpm's too. It just seems strange to me that I've isolated the sound to the top of the intake manifold. I know it's not something in the intake, but that's where it's most pronounced when checking for the loudest spot. Thanks for any help all.

Matthew

 

The quality isn't all that good it may just be my speakers but sounds like a rod knock or wristpin slap.

More that likely wristpin slap.

 

Hmmm...

Do the cylinder head valve silencers (aka Hushers) ever fall apart and make a sound all of a sudden?


The sound of a tapping valve, muted by a piece of rubber...

 

That usually sounds more like a tapping noise not a knock.

That sound clip sounds more like a knock. More specific play between the piston and the rod (wristpin slap).

 

Wouldn't I see a performance difference if that were the case? The car runs almost better than mine does, great car. It is not valve noise, it's loud enough that you can hear it idling from inside the house with the TV on. No joke.


Matthew

 

It really won't make any difference in performance at all.

A buddy of mine had a couple of car with that noise and it ran for a while before it blew apart.

 

Yep, I just did some more research on piston slap, and found a better sound file. At the bottom of this thread, there is an advertisement for pistonslap.com. I went there, and there's a clear sound file of the knocking sound. Crap. I suppose I could take the engine apart and mod it out a little bit internally for grins, hmmmm, did somebody say "project car"?

 

LOL Why not just drop a 302 in it?????

 

I found a QandA session regarding frequent problems with some cars. And with regards to my exact problem, the company rep said to look at the belts and if the upper pulleys aren't lining up with the harmonic balancer, that the harmonic balancer was the problem. He referred to it as a vibration dampener, of course. What do you think?

 

The easiest way to check is to make a mark with touch up paint or white out from the inside to out side.Then start the engine and rev it a couple of times with the A/C on and then shut it off and see if the marks moved.

I have seen about 200 bad pulleys but never heard any knock like that.

 

Right on, thanks. It may be easier to just yank the engine and drop a junkyard special in there. I can do that in a matter of a couple hours, if I don't drink while I'm doing it.

 

LOL let me know how it goes.