Need help diagnosing an engine problem.
Thread Starter
1st Gear
Joined: Mar 2012
Posts: 1
Likes: 0
Need help diagnosing an engine problem.
I have a '91 Corvette that has a noise when decelerating. It sounds to me like a knocking noise from my driver side valve cover. I have made a short video with me revving the engine, you can hear the noise as I let off the gas.
The sound isn't that good since the engine is making a bunch of noise but you can make out the knocking.
Hope someone can help!
Yes it has oil and no I haven't ran it w/o.
Thanks
Video of engine noise
The sound isn't that good since the engine is making a bunch of noise but you can make out the knocking.
Hope someone can help!
Yes it has oil and no I haven't ran it w/o.
Thanks
Video of engine noise
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
May be an extremely loose rocker arm. Take a long screwdriver and touch the pointy end to your valve cover and put your ear on the other end. Move along the length of the valve cover and see if you can hear a ticking or rattling sound. It should sound smooth like a sewing machine, if it sounds like rattling or banging it is likely a loose rocker on the cylinder.
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
It is hard to tell from sound in the video but check the valve cover to see if that is the source.
Anything to check for is an exhaust leak at the exhaust manifold. That usually makes a ticking sound...sometimes mistaken for injector noise.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
If you have roller rockers, the rocker stud may be the problem.
I had a rocker stud break while using roller rockers.
The other thing may be the rubber/silicone Y pipe mount in the middle of the car could be worn out enough to have the pipe hitting the trans on deceleration, but not on acceleration.
In addition to that, check all the bolts on serpentine belt setup, serpentine belt tensioner, crankshaft pulley, torque converter bolts, harmonic balancer ring, alternator mount, A/C compressor mount, exhaust flanges, EGR tube.
All of these things caused a "knock" on my 86.
I had a rocker stud break while using roller rockers.
The other thing may be the rubber/silicone Y pipe mount in the middle of the car could be worn out enough to have the pipe hitting the trans on deceleration, but not on acceleration.
In addition to that, check all the bolts on serpentine belt setup, serpentine belt tensioner, crankshaft pulley, torque converter bolts, harmonic balancer ring, alternator mount, A/C compressor mount, exhaust flanges, EGR tube.
All of these things caused a "knock" on my 86.
