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1996 Chevy Corvette Squeaking noise in engine

Tiny
JEFFREY39
  • MEMBER
  • 1996 CHEVROLET CORVETTE
  • V8
  • 2WD
  • MANUAL
  • 59,000 MILES
I have a 1996 Corvette with an LT4 engine that is suffering from an intermittent squeak which sounds alot like a bad bearing somewhere in the serpintine belt drive. I can remove the belt and the noise is still there and it sounds internal from underneath the left valve cover. A long scredriver used as a stethescope shows the noise most prevelent at the third bolt back on the driverside valve cover. I have had the car at a GM service center and they misdiagnosed it as a faulty flywheel and $1200 dollars later I am still faced with the same noise. The noise is there cold but gets more pronounced and rythmatic when the car is at operating temperature. Sometimes it doesn't do it at all and even when the noise is there there is no miss or loss of performance that I can tell. Can anyone please help me with a diagnosis. Thanks
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Tuesday, May 26th, 2009 AT 12:35 PM

7 Replies

Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
Tricks of the trade using a screw driver to find the squeak. Since you have eliminated the belt and pulleys. You say the noise comes from under the valve cover. I want you to try something, Is your filler cap on the side of the valve cover where the squeak is? With engine running try putting a little oil in the valve cover and see if the sweak stops or is less noticable. If it stops or is less noticable then I would think that something is not getting enough oil If it was a lifter then the engine would act diferently. I am not sure that is the problem, I can't hear the engine itself. But its worth a try and the only cost is for a little oil.
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Tuesday, May 26th, 2009 AT 1:54 PM
Tiny
JEFFREY39
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  • 4 POSTS
Thank you for your quick input. The filler cap is on the other side, sad to say, but I have removed the valve cover on this side thinking first that one of the roller rockers was bad and found everything to be clean, and well lubricated in that area. The pushrod tubes were open and oil was making it across the rocker arm to the tips of the valves. When the problem first started and at a loss for ideas, I took the car out and ran it pretty hard. The noise quit for about three weeks and has returned today. Thank you in advance for your help.
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Tuesday, May 26th, 2009 AT 2:34 PM
Tiny
JEFFREY39
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  • 4 POSTS
More information to add. The oil pressure is letter perfect accordin to the GM tech that worked on the car and when the car is on a lift you can hear the squeak from underneath as well. This is what lead the GM tech to the flywheel area thinking that the dual mass flywheel was bad, but it was not
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Tuesday, May 26th, 2009 AT 2:39 PM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
The gm tech thaught it was the flywheel. I came from a old school before computer and modern things like that. I am presuming you have a automatic transmission? There is another trick of the trade that might help figure it out. Using a small clean you don't want dirt ot anything going in your ear funnel and a piece of rubber tube that will fit on the end of the funnel tight. Slide one end on the bottom of the funnel, with the funnel part by your ear and the hose part put a various parts of the engine. It is a diferent sound and will be pronounced. You might be able to pin point the noise. I will ask another moderator about this and see what he thinks it is.
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Wednesday, May 27th, 2009 AT 1:56 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Try injecting oil in cyl no.3 and 5 and see what happens
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Wednesday, May 27th, 2009 AT 3:56 PM
Tiny
JEFFREY39
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  • 4 POSTS
Injecting the oil might be a good idea. Took the car by my brother's on the way home to let him have a listen and he came up with a good idea. Though the noise is on the side opposite the filler cap we pulled the cap with the engine running to guage the speed of the squeak compared to the rocker arm that we could see and have come to the definite conclusion that the squeak is at valve speed. In sequence with the rocker that we could see. So I feel that I am looking for a bad roller rocker arm or a bad lifter. Does anyone have any other ideas? Thanks.
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Wednesday, May 27th, 2009 AT 5:21 PM
Tiny
MIKE H R
  • MECHANIC
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I think what Raz was looking at, if you put oil in 3 and 5 cylinder, you might narrow it down.
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Wednesday, May 27th, 2009 AT 7:13 PM

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