Car is a 98 Z28 M6.


The tapping is constant at cold idle and gets louder or goes away depending on RPM. Once the car hits 210 or so degrees and is fully warmed up, the noise almost immediately starts fading in and out every few seconds like in the video above.

The noise is louder underneath the car, and seems to be coming from inside the engine. Unhooking individual coils and injectors has no effect on the noise. There was a very small amount of fine particles built up on the magnetic oil drain plug. Idles at 20psi hot on the stock gauge, 50ish psi cold.

Previous owner says they replaced all lifters with no change. Couldn't find any exhaust leaks.

I've searched quite a bit and found a lot of things to check out, but the fading in/out of the noise is quite odd and I haven't found anyone else with a similar issue like that.

 

It's your throw out bearing replace it with a GM one only don't use a aftermarket one.

 

Any reasoning behind that as far as warmed up operation, etc? Clutch is a monster stage x (they said 3, but i dont know for sure). It does seem like it could be coming from the clutch area, but it's hard to tell. The noise does not change with the clutch in or out.

 

I have heard that noise several times, almost every case I have seen the throw out bearing changes noise as the engine comes up to temperature some get louder some get quieter. Replace the throw out bearing and pilot with GM parts only.

 

That fixed my 98 M6 making that noise I hope it fixes yours.

 

The noise is a constant volume at idle cold and hot, it just fades in and out every few seconds when hot. It's very hard to pinpoint the noise, but I can see how it's coming from the clutch area and just throwing the noise forward since it does not have the little dust covers on either side and the flywheel is exposed.

 

Push the clutch in. If it still makes the noise, its not the TO bearing. Sounds like a rocker to me.

 

Sounds like lifter noise from here, try a little STP in the oil to see if it quiets it down. That's about all you can do or replace them.

 

Mine sounds exactly the same and I'm auto.

 

Mine did some weird stuff like this a while back. I change lifters and had the heads gone threw. Installed a trunion kit . No change. I had no signs of a oil pressure problem. Finally got fed up and decided to start pulling it apart until I found something or the engine was on the ground. One or the other. This is th oil pump oring I found long before I pulled the engine. I saw this so I ordered a new pump and oring and put them in ut it all back together and problem solved. About 10 more psi on the guage than I had before probably because of the new ported pump from tick. Lifters don't like air. Just a thought.

This was a factory 12 year old oil pump and oring that had never been out of the car. Shrunk up and cracked