Engine knocking noise
Thread Starter
2nd Gear
Joined: Nov 2015
Posts: 2
Likes: 0
Engine knocking noise
Hi everyone,
It's my first message on this forum!
I live in France and i have a corvette C3 of 1969.
I bought this car from the us 4 years ago.
My problem is : since the beginning, i have an engine knocking noise.
the noise looks like coming from the engine case.
2 years ago, i changed and tuned hydraulic valves but still the same noise.
When i watch videos on youtube, it looks likes a bush bearings (shells).
I continue drinving with this noise more than 5.000 miles.
When i asked to my dealer if it could be a bearings he said not it's impossible because when a bearing is dead you cannot drive more than a few kilometers.
Is that true?
What do you think of this? My knocking engine could came from bearings?
Many thanks in advance for your help,
cheers,
Norton69
It's my first message on this forum!
I live in France and i have a corvette C3 of 1969.
I bought this car from the us 4 years ago.
My problem is : since the beginning, i have an engine knocking noise.
the noise looks like coming from the engine case.
2 years ago, i changed and tuned hydraulic valves but still the same noise.
When i watch videos on youtube, it looks likes a bush bearings (shells).
I continue drinving with this noise more than 5.000 miles.
When i asked to my dealer if it could be a bearings he said not it's impossible because when a bearing is dead you cannot drive more than a few kilometers.
Is that true?
What do you think of this? My knocking engine could came from bearings?
Many thanks in advance for your help,
cheers,
Norton69
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Cut a piece of garden hose about 4 feet long. With your engine idling hold one end of the hose to your ear (while plugging your other ear) while probing over your engine with the other end of the hose. By using a hose to listen you can easily pinpoint the exact place where the noise is coming from. Quite often a knocking noise is actually a leaking exhaust manifold that makes a loud "tapping" noise when that cylinder fires. And when the engine is idling if the tapping noise suddenly gets LOUD when you suddenly open the throttle that is a sure sign of a leaking exhaust manifold.
Instructor
Joined: Oct 2012
Posts: 215
Likes: 7
From: Chardon Ohio
Probably not a bearing if you have been driving for that long with the engine noise. I'm no expert, but it sounds like may a bad hydraulic lifter. Also, if your bearing went bad your oil pressure would be low. Also could be exhaust leak....
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
It still sounds like a leaking exhaust manifold. Many people use exhaust manifold gaskets during a rebuild but those gaskets eventually burn out and then you hear a tap tap tap tap tap tap tap right where the gasket is blown out. Try the garden hose trick and see what you can find. With the engine idling probe all around the manifold where it fastens to the head. Remember to plug the ear you're not using so you can find the source of the noise easier. Foam ear plugs work great for plugging the other ear.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
Hi everyone,
It's my first message on this forum!
I live in France and i have a corvette C3 of 1969.
I bought this car from the us 4 years ago.
My problem is : since the beginning, i have an engine knocking noise.
the noise looks like coming from the engine case.
2 years ago, i changed and tuned hydraulic valves but still the same noise.
When i watch videos on youtube, it looks likes a bush bearings (shells).
I continue drinving with this noise more than 5.000 miles.
When i asked to my dealer if it could be a bearings he said not it's impossible because when a bearing is dead you cannot drive more than a few kilometers.
Is that true?
What do you think of this? My knocking engine could came from bearings?
Many thanks in advance for your help,
cheers,
Norton69
It's my first message on this forum!
I live in France and i have a corvette C3 of 1969.
I bought this car from the us 4 years ago.
My problem is : since the beginning, i have an engine knocking noise.
the noise looks like coming from the engine case.
2 years ago, i changed and tuned hydraulic valves but still the same noise.
When i watch videos on youtube, it looks likes a bush bearings (shells).
I continue drinving with this noise more than 5.000 miles.
When i asked to my dealer if it could be a bearings he said not it's impossible because when a bearing is dead you cannot drive more than a few kilometers.
Is that true?
What do you think of this? My knocking engine could came from bearings?
Many thanks in advance for your help,
cheers,
Norton69
Step One: Place member "toobroketoretire" on your ignore list.
Step Two: If this knock can be heard clearly from the bottom of the motor; While the motor is running, remove and replace one spark plug wire at a time. If a rod bearing is bad the knocking noise will be greatly reduced when you remove that cylinder's wire. If the noise is not reduced by removing the plug wires, it is likely a bad main bearing.
There are many possible sources for an engine knock. Loose pulley, disbanded harmonic balancer, loose flywheel, etc. Happy hunting!
Last edited by SH-60B; Nov 11, 2015 at 09:47 AM.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Engines With Forged Pistons
Engines with forged pistons are fairly noisy until they warm up so its always best to wait until the engine has been operated for up to an hour before trying to diagnose an internal noise. The 340 hp and up engines used forged pistons and as forged pistons have about .005" clearance they WILL make a knocking sound until they thoroughly warm up. If you remove the oil pan you can tell if the pistons are forged just by how they are made as the undersides of the pistons are very smooth with a polished appearance.
Last edited by toobroketoretire; Nov 12, 2015 at 03:26 AM.
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Racer
Joined: Jul 2013
Posts: 257
Likes: 36
Welcome to the forum.
I doubt its your bearings. Unfortunately I have first hand experience; I recently blew my motor and developed rod knock. The engine seized after about a block.
Here is a short utube video that has a good explanation/sound on the problem.
Good luck with your Vette,
Mike
Last edited by hpxt; Nov 11, 2015 at 10:38 PM. Reason: Spelling
Le Mans Master
Joined: Apr 2015
Posts: 9,428
Likes: 124
It could be exhaust leaks, and as the engine heats up they quiet from the expansion of the manifolds. Check the exhaust bolts and see if they are loose.
My first vette was a 68 with a 327 and I chased a dull knock for a year. I finally took it out and replaced it with a 427, and found several cracked piston skirts, and a loose wrist pin. Nothing broken off laying in the oil pan though.
If I had beat on it it probably would have blown up eventually.
My first vette was a 68 with a 327 and I chased a dull knock for a year. I finally took it out and replaced it with a 427, and found several cracked piston skirts, and a loose wrist pin. Nothing broken off laying in the oil pan though.
If I had beat on it it probably would have blown up eventually.