Blue Angel

2002 Z06, internally stock save for a set of PAC springs installed a long time ago due to a broken OEM spring. The engine has been running quiet and smooth since the spring install.

I've noticed an increasing noise over the past couple weeks. It is a metallic "click" or "tick" coming from the top of the engine. It is not a steady or consistent sound at idle, it's a tick - wait - wait - tick - wait tick - wait - wait - tick sort of thing.

Reving the engine up between 1500-2000 RPM increases the frequency of the tick to the point it sounds like a rattle, and not a consistent rattle, kike of like a rattle you'd hear if something was loose.

The sound comes from the top of the engine, but listening to both sides it's difficult to tell which side it's coming from.

It is a very light sound, not like heavy parts rattling inside a cast engine block or cylinder head... more like a thin metal braket rattling. Sounds more external than internal, for sure.

I've searched and found a few older posts regarding noisy fuel injectors... does that sound like something to look at? This is not a "once every" or "once every other" engine revolution type of sound, it is very random sounding and inconsistent. It's loud enough that I can hear it clearly while cruising at low speeds in 6th gear.

Wondering if anyone has had this same sound and what the solution was?

dgrant3830

There's a cheap stethscope type thing available at HarborFreight that would help you greatly in finding this sound. How many miles on the clock?

Blue Angel

I'll have to look locally... I'm in Canada. We don't have the shopping luxuries you guys are priviliged to south of the border!

Lots of miles... 193,000km (120,000mi).

2Qwik1

Check the link to this post, if yours sounds like this it's likely a failed roller lifter.

http://forums.corvetteforum.com/c5-g...ns-wanted.html

LightFighter_GXP

could be exhaust leak...... from exhaust gasket

Blue Angel

Thought of that, but an exhaust leak would be a constant noise and would follow engine RPM exactly. This is a much more random sound.

Blue Angel

I just got in from shooting a video of mine, and the video in that post sounds remarkably similar... I think I'll pull the rocker covers in the morning just in case I'm "lucky" enough to have a failed rocker. If it's a lifter I might be into a cam + lifter job. Not what I was hoping to hear!

Thanks a bunch for that link!

ZZ06

you mean valve covers. Thats what i would do. Pull it and have a look see

Blue Angel

Rockers cover the valves, rocker covers cover the rockers.

butch2000

check the push rods as well , I have replaced alot of these in the 5.3 trucks , due to wear ,from high miles, they sound the same as what you are describing ?

Blue Angel

Well, I tore the top of the engine apart yesterday and springs, rockers and pushrods are all there and all look 100% perfect... the pushrods are all straight with no wear on the ends and the rockers all have just a little bit of play (normal I think) and are still full of needle bearings.

Sounds like I'm into pulling the heads and changing the bad lifter at a minimum, and will likely have to change the cam eventually as well as reading has shown others to have scored camshafts after failing rockers. For now I may just pull the heads and look at the lifters and change the bad one, then plan on a full set of lifters and a cam in the very near future.

Does anyone have a link to a good thread showing cylinder head removal in car? I just did some quick searching and came up empty. I'm pretty sure from a tools standpoint I've got it covered, but seeing someone else walk through it could point out any "surprises" ahead of time.

Thanks!

Eric D

Before pulling heads I would suggest running the engine with the covers off and using a stethoscope with a metal tipped probe. With the engine idling, listen to each rocker hold-down bolt. You will be able to tell the offending cylinder. It would be worth swapping rockers and pushrods with a different cylinder to see if the issue follows the rocker or stays at the original offender.

Improper cam lobe heat treat can cause the lobe to spew pieces of its self which then chew up the lifter rollers quickly. Here is an example:

These are good rollers -



This is a bad one caused by a bad cam -



This is what a bad lobe looks like -

dgrant3830

The hardest part of removing the heads is getting the power steering pump pulley off as its a press-on fit. Not sure you have a bad lifter though. I finally lost a lifter(s) at 274k miles and their issue started with tapping on cold startup due to the lifter(s) bleeding down when cold. The problem slowly got worse till it got very bad.

Got uid0

could it be the common piston slap noise?

Blue Angel

Nah, I've ruled that out. This is a very odd sounding "tick" at idle, and a "rattle" at higher RPM. It was very loud when starting the engine after having the top end disassembled. I've had the car since '04 and have never heard anything like this before.

Blue Angel

Yes, I've read the same elsewhere... I plan to start on the passenger side and hope the offending lifter is there.

When you pulled the lifters could you see what was wrong with them? The video link provided above sounds almost identical to my issue. The failure there was needle bearing failure on the roller tip.

I lost a valve spring a while ago (got lucky and just neede a spring and pushrod) and the pushrod was bent, so I'm thinking that may be the lifter that's gone. The the spring coils wound together and "bound", forcing the pushrod to bend. That may have been the start of the demise of this lifter (assuming it's just one that's bad).

As you've suggested and I've read elsewhere, lifters in a stock engine normally last much longer than this, though it is an LS6 which would put more stress on the lifter than the LS1 valvetrain would... still seems premature, though.

Blue Angel

Thanks for the great pics!

Do you think a heat treatment issue would show up long before now? The car has 120k miles on the clock... See my post above; I'm thinking it may have been the cylinder that lost and exhaust valve spring a while ago.

dgrant3830

Its highly unlikely that a lifter has failed this early on you although not impossible. Even on mine at 274k miles, the bad lifter was not obvious at all and mine was really bad as far as tapping to the point of clattering loudly. I would be looking at the rocker arm bearings as already mentioned but you indicated they were fine. How have you been driving your car, as in tracking or just daily driving? Lots of high RPM runs of any kind? How is your oil pressure?

Blue Angel

Yep - pulled all of the rockers and they all look great, have the same amount of freeplay and appear to have all of their needle bearings in place on both sides. Pushrods have no visible wear on the ends and are straight. Retainers and keepers are all in place, springs are centered.

For the most part just Daily Driving with the odd rip through 1st, 2nd and 3rd. Nothing sustained at high RPM, and mostly (like > 98%) cruising below 2000 RPM.

Oil pressure is fine, always over 35psi hot at idle and higher with lower oil temps.

dgrant3830

I suppose the last thing you can try then is to remove the accessory belts including the compressor belt and start it up again, just in case the noise is related but its sounding like your original thoughts may be correct.

Know that you must buy a new set of head bolts too as they are stretch to torque, along with the new gaskets and etc...

If a lifter(s) is trashed, you could be looking at a new cam as well along with further disassembly to get it out, more gaskets and so on.