Strange knocking sound
#1
Strange knocking sound
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
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
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#7
RE: Strange knocking sound
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"?
#9
RE: Strange knocking sound
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?
#10
RE: Strange knocking sound
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.
I have seen about 200 bad pulleys but never heard any knock like that.
#11
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