help! knocking noise!
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Teching In
Joined: Oct 2011
Posts: 19
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From: san jose ca.
help! knocking noise! Soo the other day my car started knocking when I turned it on in the morning. But when it warmed up the knocking went away? I'm thinking the valves? Any idea what else it can be? I also have a oil pan leak idk if that might affect anything? Thanks guys
TECH Fanatic
Joined: Jan 2010
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From: Euless Tx
Yeah, it's common with GM vehicles. It happens because the clearance between the piston and the cylinder bore is too much, cause the "slapping" noise that you hear on a cold start. I'm not saying that's what your problem is, but if it happens only on a cold start, then goes away, I would put my money on it.
Does piston slap happen "all of a sudden", or do you guys think the OP would have heard it gradually developing over time? I mean you don't just drive a car for 90,000 miles, wake up one day, and have piston slap, do you?
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TECH Fanatic
Joined: Jan 2010
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From: Euless Tx
OP, it won't hurt anything. But again, that may not be what your problem is. Do you have a video of it you can post?
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I have the same issue right now on a freshly built engine and I am having the heads taken off because we think its a lifter that is not pumping up and causing the noise. it increases with RPMs and its not there all the time. The oil pressure gauge trembles slightly so we think that it makes sense that the lifter is causing that oil pressure phenomena.
