tapping sound
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
tapping sound
This is a 96 C4 LT1 at start up it is very quite, after 15 or 20 sec. a slight tapping appears and get's louder, when it gets louder it sounds like it's metallic. mainly on the drivers side. after the motor get's hot the tapping sound get lower and lower to a point after about 15 or 20 minutes it is barely noticeable. Turn the car off let it sit 10 or 15 minutes, start the motor a slight tap appears, then seems to go away.
Replaced al lifters with Delco push rods are straight appear to be ok. When listening to the motor underneath behind drivers side tire it is extremely louder. Also tapping sound seems to be in rhythm with the of the exhaust. Can any one point me in the right direction.
Replaced al lifters with Delco push rods are straight appear to be ok. When listening to the motor underneath behind drivers side tire it is extremely louder. Also tapping sound seems to be in rhythm with the of the exhaust. Can any one point me in the right direction.
Melting Slicks
Joined: Nov 2007
Posts: 2,830
Likes: 147
From: Gainesville FL
This is a 96 C4 LT1 at start up it is very quite, after 15 or 20 sec. a slight tapping appears and get's louder, when it gets louder it sounds like it's metallic. mainly on the drivers side. after the motor get's hot the tapping sound get lower and lower to a point after about 15 or 20 minutes it is barely noticeable. Turn the car off let it sit 10 or 15 minutes, start the motor a slight tap appears, then seems to go away.
Replaced al lifters with Delco push rods are straight appear to be ok. When listening to the motor underneath behind drivers side tire it is extremely louder. Also tapping sound seems to be in rhythm with the of the exhaust. Can any one point me in the right direction.
Replaced al lifters with Delco push rods are straight appear to be ok. When listening to the motor underneath behind drivers side tire it is extremely louder. Also tapping sound seems to be in rhythm with the of the exhaust. Can any one point me in the right direction.
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
Not much info, but here goes...If your are sure it's internal...
Check the rocker arms. Could be one cracked, or galled from the pushrod. Look at the valve stems while the rockers are off for excessive wear also. Keep in mind you will have to adjust the valve when you put the rocker nuts back on.
If that checks out, and you're sure it isn't a lifter, unplug 1 spark plug wire at a time on the noisy side . If the sound goes away or changes, that is likely the cylinder to examine. Bearing could be going, but it doesn't sound like it. Sounds like the metal is expanding once the engine gets warmed up, and tightens the engine tolerances on the offending parts..
Is it a high mileage engine?
Check the rocker arms. Could be one cracked, or galled from the pushrod. Look at the valve stems while the rockers are off for excessive wear also. Keep in mind you will have to adjust the valve when you put the rocker nuts back on.
If that checks out, and you're sure it isn't a lifter, unplug 1 spark plug wire at a time on the noisy side . If the sound goes away or changes, that is likely the cylinder to examine. Bearing could be going, but it doesn't sound like it. Sounds like the metal is expanding once the engine gets warmed up, and tightens the engine tolerances on the offending parts..
Is it a high mileage engine?
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
Not much info, but here goes...If your are sure it's internal...
Check the rocker arms. Could be one cracked, or galled from the pushrod. Look at the valve stems while the rockers are off for excessive wear also. Keep in mind you will have to adjust the valve when you put the rocker nuts back on.
If that checks out, and you're sure it isn't a lifter, unplug 1 spark plug wire at a time on the noisy side . If the sound goes away or changes, that is likely the cylinder to examine. Bearing could be going, but it doesn't sound like it. Sounds like the metal is expanding once the engine gets warmed up, and tightens the engine tolerances on the offending parts..
Is it a high mileage engine?
Check the rocker arms. Could be one cracked, or galled from the pushrod. Look at the valve stems while the rockers are off for excessive wear also. Keep in mind you will have to adjust the valve when you put the rocker nuts back on.
If that checks out, and you're sure it isn't a lifter, unplug 1 spark plug wire at a time on the noisy side . If the sound goes away or changes, that is likely the cylinder to examine. Bearing could be going, but it doesn't sound like it. Sounds like the metal is expanding once the engine gets warmed up, and tightens the engine tolerances on the offending parts..
Is it a high mileage engine?
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
[QUOTE=in distress;1596055779]I only had the car a little over a year the speedometer was 47,347 not really sure if that is true. Thanks I will try the spark plugs wires. I also was told that you can replace the dash.Also it does not go away at higher RPM
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Any work prior to noise? Oil pressure? If oil has some miles drain oil and cut open oil filter check for metal with magnet. Look for silver or gray material in filter. Bore scope would be handy to look at cylinder walls and top of piston. If piston is shiny on the outside and dark in the center, bearing could be on the way out, piston maybe contacting head. It could be an exhaust leak, they can be pesky and have a tapping sound. A stethoscope with a tube in place of probe works pretty good. Make sure bolts are tight. I would hope for exhaust leak.
Safety Car
Joined: Apr 2016
Posts: 4,648
Likes: 1,059
From: N.E. Ohio OH
Finalist 2020 C4 of the Year - Modified
a cardboard wrapping paper tube works wonders for listening through, as the above folks have mentioned to use a tube. it is long enough to put in places and won't seriously hurt you if you bump a moving part. if you don't have a partially empty roll you can steal the tube from, go to the dollar store and sacrifice a dollar.
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Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
Any work prior to noise? Oil pressure? If oil has some miles drain oil and cut open oil filter check for metal with magnet. Look for silver or gray material in filter. Bore scope would be handy to look at cylinder walls and top of piston. If piston is shiny on the outside and dark in the center, bearing could be on the way out, piston maybe contacting head. It could be an exhaust leak, they can be pesky and have a tapping sound. A stethoscope with a tube in place of probe works pretty good. Make sure bolts are tight. I would hope for exhaust leak.
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
tapping sound
Any work prior to noise? Oil pressure? If oil has some miles drain oil and cut open oil filter check for metal with magnet. Look for silver or gray material in filter. Bore scope would be handy to look at cylinder walls and top of piston. If piston is shiny on the outside and dark in the center, bearing could be on the way out, piston maybe contacting head. It could be an exhaust leak, they can be pesky and have a tapping sound. A stethoscope with a tube in place of probe works pretty good. Make sure bolts are tight. I would hope for exhaust leak.
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
tapping sound
Can not seam to get to # 8 spark plug wire at the very rear of the motor on passenger side this is 96 LT 1 any suggestions.
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
Advanced
Joined: Dec 2016
Posts: 65
Likes: 3
a cardboard wrapping paper tube works wonders for listening through, as the above folks have mentioned to use a tube. it is long enough to put in places and won't seriously hurt you if you bump a moving part. if you don't have a partially empty roll you can steal the tube from, go to the dollar store and sacrifice a dollar.
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
Drifting
Joined: Feb 2016
Posts: 1,384
Likes: 339
From: Simi Valley CA
Have you ruled out an exhaust leak? On one of my first cars, a 67 Mustang, I had that exact issue. I replaced the lifters, changed to roller rockers, plugs, etc. My friend came along and pointed it out right away. The exhaust heats up quickly and the gaskets flex.
Thread Starter
Heel & Toe
Joined: Nov 2017
Posts: 15
Likes: 0
From: port st lucie florida
tapping sound
I already ordered the rockers & pushrods If that doesn't do the trick before go after valves I will check the exhaust. If I had a carburetor I used to pure some STP in it and watch for smoke, don't know if I can do that with a throttle body.