Need some help diagnosing this problem (video)

**turo** · 02-08-2010, 06:40 AM

The car is an 01 Z28 (M6) with bolt-ons and an F13 cam, 99k miles on the odometer. This ticking developed a few days ago on my way to work. I've done several searches on here and youtube comparing this noise to common noises (belt tensioner, lifters, pushrods), but none of them sound the same as this one to me. The noise is there all the time (idle, acceleration, deceleration), and varies according to the rpms. Any guesses where I can start to look?

I changed the oil yesterday, it did not smell burnt and there were no metal shavings in the oil/plug, oil pressure is good. I haven't ruled out belt/pulley issues, but I wasn't sure how to test for that (I can't start the engine with no belt, can I?). Tomorrow I have the day off so I plan on pulling the valvecovers and checking the rockers/pushrods/valvesprings.

I can't really afford to take it to a mechanic right now, so any help is greatly appreciated!!!

2/29 UPDATE: Pulled the valve covers and checked the valvesprings/rockers/pushrods. I couldn't find anything damaged, all seems to be in good shape. I guess the next thing to check would be the lifters.

[ame="http://www.youtube.com/watch?v=eHsz7qStdlA"]http://www.youtube.com/watch?v=eHsz7qStdlA[/ame]

**Smittro** · 02-08-2010, 08:02 AM

I dunno sounds like a lifter to me. Maybe you have a bent push rod.. Definetly does'nt sound like the bottom end to me.. However this maybe a long shot but I have heard a similar noise from a leaking exhaust mani and headers..

**JaycenK** · 02-08-2010, 11:19 AM

sounds metalic though. More than likely valve train. Not like a bottom end knock. Need to see if you can tell what side it is comming from and pull a valve cover. If not both and find it.

**V8MUSCLE** · 02-08-2010, 07:43 PM

i think i hear an air leak aswell. does it get quieter when the car is warm?

**Hi-Po** · 02-08-2010, 08:05 PM

That's a pretty good noise you have going on there. Your on the right track though. Take the valve covers off. Inspect for obvious. It may be a push rod, but I doubt it if you haven't mechanically over revved the engine. (Have you?). But it needs to be checked. What valve springs were used? Stock lifters? How many miles on them? Whats RPM does the car see on a daily basis? I see the F13 cam. Its very possible a lifter problem, sadly. You can start the car for a minute without a belt to see if that's it. Don't leave it running or anything obviously. Long shot, but its for sure worth a shot. Has there been any recent work performed?

Go to the auto parts store and buy a 5 dollar mechanic stethoscope. Start probing around, see it you can pin point the noise.

**turo** · 02-08-2010, 08:15 PM

Thanks for the replies, guys. To answer your questions: the noise does not go away when the car is warmed up, it actually does not change at all. The engine has not been over-revved, it has been my daily driver for the past 4 years and has honestly not seen RPM's higher than about 3000 on a daily basis (slow driving in traffic to-from work). The cam was installed about 6 years ago along with PRC springs, all have 50k miles on them. The lifters are stock, so they have 99k miles on them. No recent work done on the car, the most recent thing was probably about 5 years ago. I'll pop the valve covers tomorrow and see what I find. Thanks for all the help/suggestions so far, I'll keep you all updated.

**Hi-Po** · 02-08-2010, 08:23 PM

6years/50K miles on those springs would have me really ancy to change them.

Pop those valve covers and check everything out and get back to us.

**pk222** · 02-09-2010, 09:37 AM

Any chance when you take off the oil filler cap that the noise gets louder? That might be able to rule out the pulleys and belt? Not to sound dumb but that sounds a lot like the noise I'm trying to track down on my car but mine isn't that loud yet. Are you getting vibrations from the engine?
My engines all stock but it seems like thats really close to the noise I'm getting

**turo** · 02-09-2010, 10:19 AM

Well, I popped off the valve covers this morning. I went through and checked the valvesprings, rockers, and pushrods. Everything looked good, I couldn't see anything cracked/bent/broken. I didn't pull the heads off the car, so the back springs on the passenger side were very difficult to inspect with the limited amount of space, but from what I could tell nothing was wrong. I guess the next thing to check would be the lifters. I'm going to have to wait until the weekend to dive into that project, since I've never pulled the heads off before.

Any chance that it could be anything else other than a bad lifter? I'd hate to go through all that work and put it back together only to start it back up and hear that damn noise again!

**pajeff02** · 02-09-2010, 10:28 AM

It is too metallic sounding for a header leak... and quite loud. In lieu of a stethoscope, you can use a piece of wood pressed against different parts of the motor. Place your ear against the other end and try to locate the area of the noise. Just be careful you do not get tangled up in the belts. How about dropping your oil and filter to see if you have any shavings? You'll have to cut the filter open to inspect it.

**Hi-Po** · 02-09-2010, 10:47 AM

Cutting the filter open (if you still have it from your last change) is a good idea.

**turo** · 02-09-2010, 10:52 AM

I used a large screwdriver as a stethoscope, and heard the noise just slightly louder in the driver's side (putting the screwdriver on the top of the head near the intake manifold). I changed my oil on Sunday and didn't see anything at all in the oil, but I do still have my filter. I'll try and cut it to see if I find anything in it.

**T-Rexxx** · 02-09-2010, 03:14 PM

Sounds like exhaust/combustion is leaking from somewhere. It might be blow back from a bent push rod or a collapsed spring that is not letting the valve close all the way. It sounds like it is only on one cylinder though. I hope you don't have a bad cam lobe.

**Smittro** · 02-09-2010, 07:09 PM

I still say it sounds like a lifter..imho

**0rion** · 02-09-2010, 09:22 PM

it could very easily be a collapsed lifter.....my initial thought was a broken valve spring.

**Hi-Po** · 02-09-2010, 09:24 PM

Broken valve spring was one of the first thoughts for sure. It seems to be pointing towards a lifter now if the top end valve train all checked out.

**pajeff02** · 02-10-2010, 04:37 AM

I have never had a hydraulic lifter go bad on any of our cars -- how do you find the offending one? My understanding is that you can not simply look at it and see that it is bad. Nor can you turn the motor and find a difference in the pressure on the pushrod as they need oil pressure to pump up. Granted, if I had one go I would replace all of them, but I am curious.

**Smittro** · 02-10-2010, 09:10 AM

Originally Posted by pajeff02

I have never had a hydraulic lifter go bad on any of our cars -- how do you find the offending one? My understanding is that you can not simply look at it and see that it is bad. Nor can you turn the motor and find a difference in the pressure on the pushrod as they need oil pressure to pump up. Granted, if I had one go I would replace all of them, but I am curious.

How I do it is take the valve cover off, bundle up a good shop rag and put it in the palm of my hand. I then (engine running be carefull) push or sort of lean on the backs of each rocker. When you get to the bad/effected one the tap/chatter pitch will change. That's how I do it don't see why the same thing could'nt be done on any push rod engine. Down side is it can be messy and there's not much room under our hoods... But the engine bay aways needs cleaned anyway

**pajeff02** · 02-10-2010, 10:58 AM

Originally Posted by Smittro

How I do it is take the valve cover off, bundle up a good shop rag and put it in the palm of my hand. I then (engine running be carefull) push or sort of lean on the backs of each rocker. When you get to the bad/effected one the tap/chatter pitch will change. That's how I do it don't see why the same thing could'nt be done on any push rod engine. Down side is it can be messy and there's not much room under our hoods... But the engine bay aways needs cleaned anyway

Great idea -- I wondered how the heck you could find the bad one.

**silverWS6** · 02-10-2010, 09:04 PM

I haven't read all the above post but i'm gonna ask anyways... Did you actually remove every pushrod and roll it over glass to see if any of them was bent?