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Recently my 2003 Z06 started to make a knocking noise from under the hood and I'm having a hard time pinpointing it.
Long story short, the harmonic balancer failed and the car sat for 2 weeks while i collected parts/tools/research before tackling the job. Got it all buttoned up and started it for the first time in 2.5 weeks and was greeted with a very loud knocking noise that seem to be coming from cylinder 1 and 3. I used a stethoscope and the noise is definitely louder on the valve cover, than on the cylinder head at 1 and 3. . It was not doing this before replacing the balancer, so it seems odd to me that it would be rod knock. A collapsed lifter would make the most sense, however i dont feel the noise matches that diagnosis. I have pulled the valve covers and cranked the engine (fuel pump relay removed) to watch everything in the valve train. All appears to operate correctly and there is no noise at cranking speed. I have also tried pushing on the push rods to see if i could locate a collapsed lifter and none budge... I also pulled the push rods on 1 and 3 as that seems to be where the noise is most prominent but they look great. I think this is way to loud to be piston slap, but i have not let it run long enough to warm up as i do not want to cause any more damage. I don't think it is an exhaust leak as i have not messed with that system but i suppose anything is possible...?
There is no CEL, and there are no stored codes in the DIC
Does anyone have any suggestions to help isolate the issue before i tear anything down?
Rob - Anything is possible i suppose. I just found it odd that it was running quietly prior to replacing the balancer issue. If i spun a rod, would it not have been knocking before?
Originally Posted by Bill Curlee
Pop off the valve cover and start there.
BC
Bill - I already pulled the valve covers and inspected. No noticeable damage. I also pulled the rockers off, and the push rods out to inspect. They all looked fine, and i used a straight edge to check if the push rods were bent.
I would NOT continue to run the engine if it were my car..... JMHO
8VETTE7 - All of the valve springs look to be in 1 piece with no noticeable breaks or cracks. I have pulled the valve covers and cranked the engine while watching everything in motion as well. I have run the engine for all of maybe 3 minutes total since the noise started. Most of them in short 15-20 sec intervals. The 2 minute video was the longest stretch but i agree. I will not be running the engine anymore until i find and replace what ever the failed component is...
Thanks for all your inputs so far.
Last edited by ezstreet; Jul 25, 2016 at 11:53 AM.
Could it be a bad exhaust manifold gasket? It does sound more like valvetrain the second time I listened. The squeak sounds like a water pump or alternator? Just my $0.02 Hope you find it...
Hard to say, but I'm thinking lifter noise. If it were me, I'd try to flush the affected lifters with some chemtool b12 by spraying straight down the center of the pushrods into the lifters, followed by a motor flush.
Thanks for all the ideas and opinions. When i get home tonight i will check the exhaust header bolts to make sure they are all tight, then pull the belt and see if the noise persists. I have been researching these videos and they sound very similar to my noise...
If that doesn't take care of the issue i will be draining the oil and checking for sparkles. Then i plan on starting to pull the heads and dive in...
Checked all the header bolts and i did find one of the center bolts on the driver side was a little loose. I tightened it up, but that did not solve the issue. I removed the serp belt and that had no effect on the sound either.
I probed around more and it seems the noise is coming from underneath the intake manifold on the driver side.
Soooooo... In i went! After about 1.5 hrs this is where i called it a night.
Vacuum all that crap out and remove the valley cover plate. Then you can see most of the cam lobes and lifter rollers. You can also see the upper cam gear and chain.
Vacuum all that crap out and remove the valley cover plate. Then you can see most of the cam lobes and lifter rollers. You can also see the upper cam gear and chain.
BC
That is the plan after work tonight, i will post up more as i get further. Hope this can help someone else who may have the same issue.
I spent about another 2hrs last night working on tear down. Some parts get very tedious to remove with the engine still in the car.... It is exhausting turning bots 1/8th turn at a time
Does anyone know how to remove this from the back of the manifold? It is held together with a bunch of zip ties... PO must taken it in for a shoddy repair...
This is after i cut about 4 more zip ties off just to get the intake out of the engine bay.
Where I left off the night before
Valve cover removed
Front of engine under top plate. Really cant see as much as i thought i would be able too
Rear of engine under top plate
Rockers and push rods removed
Makeshift organizer to keep rockers and rods in the correct order
So far i have not found the source of my issue. More progress will be made tonight i hope
WOW! All that and no results yet... Do you have access to a bore scope?
The Fitting on the back of the manifold: I "THINK" the zip ties are being used to secure the MAP sensor onto the vacuum fitting on the back of the intake.
That intake fitting is secured by a plastic C Clip on the "INSIDE" of the intake manifold. Its not easily removed and not designed to come out.
The fitting is sealed with a big orange O ring and the fitting will seem LOOSE in the socket. That's normal unless it ready to fall out loose.
take the ZIP ties off the MAP SENSOR and see if its damaged and will not stay in the fitting by its self. It should POP In and stay in the fitting. If its loose, you may need a new MAP sensor or use the ZIP TIES.
Last edited by Bill Curlee; Jul 27, 2016 at 11:17 AM.
WOW! All that and no results yet... Do you have access to a bore scope?
The Fitting on the back of the manifold: I "THINK" the zip ties are being used to secure the MAP sensor onto the vacuum fitting on the back of the intake.
That intake fitting is secured by a plastic C Clip on the "INSIDE" of the intake manifold. Its not easily removed and not designed to come out.
The fitting is sealed with a big orange O ring and the fitting will seem LOOSE in the socket. That's normal unless it ready to fall out loose.
take the ZIP ties off the MAP SENSOR and see if its damaged and will not stay in the fitting by its self. It should POP In and stay in the fitting. If its loose, you may need a new MAP sensor or use the ZIP TIES.
Thanks for the info on the sensor!
I do not have a bore scope, thought about getting a cheap-o from Harbor Freight on the way home from work tonight.
I do have the plugs removed from the head and they are all gaped at .040, and no carbon or fuel fouling.
WOW! All that and no results yet... Do you have access to a bore scope?
The Fitting on the back of the manifold: I "THINK" the zip ties are being used to secure the MAP sensor onto the vacuum fitting on the back of the intake.
That intake fitting is secured by a plastic C Clip on the "INSIDE" of the intake manifold. Its not easily removed and not designed to come out.
The fitting is sealed with a big orange O ring and the fitting will seem LOOSE in the socket. That's normal unless it ready to fall out loose.
take the ZIP ties off the MAP SENSOR and see if its damaged and will not stay in the fitting by its self. It should POP In and stay in the fitting. If its loose, you may need a new MAP sensor or use the ZIP TIES.
Bill,
Seeing in an earlier pic a blower would the MAP sensor still be secure when there's positive pressure in the intake manifold?
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Help pinpoint engine noise
