Roys92BlackRose

OK, I've searched this forum and the Internet and can't find my specific issue. My 92 coupe makes a fairly pronounced tapping/clicking/clacking noise upon acceleration when the engine is cold. It seems to be coming from the driver's side only. It synchs with engine rpm and disappears after about 5 minutes of running. I usually let the engine idle upon startup for about 15 to 30 seconds before driving, and am easy on the go pedal until the coolant temp reads above 150 degrees. The sound is only noticeable when accelerating.

I've read that it could be piston slap, clicking injector, lifters or exhaust leak and I don't know what direction to go. I thought about having a mechanic check it out but the noise would be gone by the time I drove it to him. He'd have to keep it overnight I suppose.


Thought I would check in with the gurus here before tearing anything apart.

John A. Marker

I would start off using a small rubber hose as a listening device and start the engine and hive the hose around each of the exhaust ports to see if there is an exhaust leak.

If you have ruled out the exhaust, then remove the valve cover. Start the car and use the hose or stethoscope and move from one rocker arm to the next to see if you can locate the source of the noise....lifter...injector or other.

Do you know if the engine has been rebuilt? Piston slap is usually associated with an after market piston rather than stock.

Roys92BlackRose

I have done those things and I hear a lot of valve train noise but the sound I am describing is only audible when actually driving the car under load. I also inspected around the exhaust manifold for telltale streaks but could find nothing. The car only has 60k miles and has not been rebuilt to my knowledge, and like I said, the noise goes away within 5 minutes of driving.
Is it possible to have only one piston making slapping noises? I suppose the sound could also be an exhaust leak further down the pipe at one of the connections. I only suspect it is an exhaust leak because it does go away when hot, which seems to indicate heat expansion sealing things up. Also, I did not see any manifold cracks which apparently are an issue with the lt1 engine.

enventr

Check all of the exhaust bolts to see if they are tight. One of my cars I previou owned had the same problem and it was 4 years old. I took it to the dealer and he said one bolt was slightly loose enough to create that ticking sound until it warmed up and the heat sealed it so ticking went away. Sounds like the same issue

DinoBob

99% it's an exhaust manifold leak.

DinoBob

Get a can of Seafoam. Take a vacuum hose, and, with the engine running, suck a *little* bit of Seafoam into the hose. The result will be a fabulous smoke show out the exhaust, which will reveal an emanation of smoke from the source of your leak.

Exhaust manifold leaks manifest themselves as loud ticks which sound like a really bad lifter tap. Then as the cast iron expands they get much quieter. I have had several experiences with them including on my L98. A loose bolt was my issue.

Roys92BlackRose

OK, thanks a bunch. I will check the bolts. I looked at them yesterday and they seemed tight but I didn't break the tools out. Will do today.

Roys92BlackRose

Happy to report that the front drivers side exhaust manifold bolt was completely loose and hanging out of the hole. Removed the alternator, AC compressor, and splash shield to gain access but finally got it tightened up. Can't drive it today but I'm confident that my issue is resolved.

gerardvg

Great news, I know the noise well the header bolts come loose occasionally and makes a ticking noise when loose.

I doubt you have any engine problems, they are fairly bullet proof.

Paul Workman

Hope the bolt is all it was.

Here's something I read about that seems to be working as well:

With new exhaust gaskets, I smear some RED (HIGH TEMP) RTV on the head-side of the gasket before installing the gasket and the exhaust manifold.

(This was a recommendation for LT5s, especially w/ aftermarket headers prevents a few flange bolts from being used. The RTV is there as an insurance policy, and it seems to work 100% of the time for me...so far. Curious to know what others have experienced when doing the same with whatever motor?)

John A. Marker

The exhaust was my first thought. This is why I suggested using a hose to listen around the ports. Just looking for a deposit of exhaust gases on the head or around the port often does not tell the whole truth whereas using the hose most often identifies the leak.

Very glad you found it and it was a easy fix.