good luck
Metallic tapping noise from engine
Thread Starter
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Metallic tapping noise from engine
Engine: Mark IV 454 with mods as per sig. Daily driver. 50K miles since rebuild.
For about a week now it has made a tapping noise after it fully warms up. There is no noise at all when cold.
Noise is coming from underneath the engine. I think more drivers side than passenger, but not sure. Noise is almost inaudible from the top. I put a hose to the valve covers and listened and there is no noise from the valve covers.
The noise is not coming from the front of the engine.
I revved the engine in neutral and let off but didn't hear the tell tale loud tapping as the engine slows down that I've come to associate with a spun rod bearing.
I checked for exhaust leaks and couldn't find any. I've had exhaust leaks before and this doesn't sound like one anyway. It has a sharper note to it.
Any ideas? Bearings? Oil pump? Oil pressure is the same as it has always been: 40 PSI hot idle, ~55 PSI going down the road.
I'm thinking I'll throw a set of rod bearings at it but might just be wasting my time?
For about a week now it has made a tapping noise after it fully warms up. There is no noise at all when cold.
Noise is coming from underneath the engine. I think more drivers side than passenger, but not sure. Noise is almost inaudible from the top. I put a hose to the valve covers and listened and there is no noise from the valve covers.
The noise is not coming from the front of the engine.
I revved the engine in neutral and let off but didn't hear the tell tale loud tapping as the engine slows down that I've come to associate with a spun rod bearing.
I checked for exhaust leaks and couldn't find any. I've had exhaust leaks before and this doesn't sound like one anyway. It has a sharper note to it.
Any ideas? Bearings? Oil pump? Oil pressure is the same as it has always been: 40 PSI hot idle, ~55 PSI going down the road.
I'm thinking I'll throw a set of rod bearings at it but might just be wasting my time?
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
i've had trouble in the past with the TRW forged piston with the long oiling slot. Due to improper clearance the skirt would break off but continue to move up and down with the piston. It makes more of a clacking sound rather than a knocking. I drove myself nuts trying to figure it out replacing cam, lifters and rod bearings. I hope that's not what it is because it means a total rebuild.
Are you sure its not a lifter or fuel pump pushrod?
Do you have an engine stethescope to try and pinpoint the noise?
Are you sure its not a lifter or fuel pump pushrod?
Do you have an engine stethescope to try and pinpoint the noise?
Last edited by turtlevette; Feb 6, 2006 at 12:31 PM.
Thread Starter
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Not sure about anything. Just guessing at this point.
I need to pick up a stethoscope.
Electric fuel pump, so that's out. Unknown pistons, but I'm pretty sure not forged. Stock style rebuild done by previous owner. Probably cast or hyper pistons.
Could be a lifter but I expected to hear noise from the valve covers.
I need to pick up a stethoscope.
Electric fuel pump, so that's out. Unknown pistons, but I'm pretty sure not forged. Stock style rebuild done by previous owner. Probably cast or hyper pistons.
Could be a lifter but I expected to hear noise from the valve covers.
Race Director
Joined: Feb 2005
Posts: 16,100
Likes: 17
Many years ago I picked up a similar noise at an autocross...we all thought it was bearings...dropped pan and everything was cool...bottoned it up and someone suggested carbon...which normally comes higher in engine(sound)(we were confused where).. So we misted water down carb at 1500-2000 RPM...noise went away..Suggest you give that a shot...also,listen at pan,lower block with hose if you can get it on ramps...let someone rev it for you....
Rich
Rich
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Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Recently found my pushrods with the ends that are pressed/welded in had a few loose ends that contributed to a noisy valvetrain. Previously eliminated potential exhaust leaks, cam wear, defective lifters, rockers, springs etc.
Replaced with hardened one-piece pushrods on left bank and sound decreased significantly. Replacing right ban of pushrods next week.
Replaced with hardened one-piece pushrods on left bank and sound decreased significantly. Replacing right ban of pushrods next week.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Originally Posted by zwede
Any ideas?
2 Listen at flywheel area.
Last edited by Ganey; Feb 6, 2006 at 02:57 PM.
Melting Slicks
Joined: Jan 2003
Posts: 2,713
Likes: 31
From: Shreveport LA
LA Events Coordinator
Had the VERY SAME thing happen to me....check out my thread and the responses I revceived.
http://forums.corvetteforum.com/show...y75&forum_id=3
The only thing left to replace, for me, is the crankshaft & bearings. Took it into Red River Chevy today to have the engine pulled & new crank with bearings (SCAT Performance Steel Crank) installed.
Good Luck!
http://forums.corvetteforum.com/show...y75&forum_id=3
The only thing left to replace, for me, is the crankshaft & bearings. Took it into Red River Chevy today to have the engine pulled & new crank with bearings (SCAT Performance Steel Crank) installed.
Good Luck!
Thread Starter
Race Director
Joined: Sep 1999
Posts: 11,360
Likes: 382
From: Plano TX
Problem solved and it turned out to be rather silly. All it was, was a wire rattling against the firewall metal heatshield. Tied everything up with some zip ties and no more noise. Surprised me it could be loud enough to hear inside the car with windows up.
