turbo c5 engine noise
Thread Starter
Racer
Joined: Jun 2011
Posts: 405
Likes: 5
turbo c5 engine noise
After a real short pull the other day on decel I started hearing a tapping/knocking. Oil pressure still looks perfect
When I got the car home I pulled the valve covers, didn't see anything broken.
Using a stethoscope it sounds like the noise is louder coming from the front of the motor near the cam.
I'm hoping that it is a failed lifter but I don't know how to check for that. Would a compression test show that
When I got the car home I pulled the valve covers, didn't see anything broken.
Using a stethoscope it sounds like the noise is louder coming from the front of the motor near the cam.
I'm hoping that it is a failed lifter but I don't know how to check for that. Would a compression test show that
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Noises are SOOOOO, difficult to diagnose over the net. If you can shoot a short video it may make the diagnosis a little easier.
Some common things to check:
Rocker Trunions (Tiny roller bearings fall out)
Bent pushrods
Bill
Some common things to check:
Rocker Trunions (Tiny roller bearings fall out)
Bent pushrods
Bill
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Can you take the serpentine drive belt off and run the engine and see if its an accessory driven noise? Easy enough to do and it will not hurt anything. That eliminates a LOT of things.
Yep, pretty hard to pin point.
Bill
Yep, pretty hard to pin point.
Bill
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
OUCH! 
When you revved it I cringed!
Get a mechanics Stethoscope or make one. ( Four foot long vacuum line, stick a small screw or metal rod into one end of the hose), put the other end into your ear, place the screw end on top of the valve cover over each valve rocker and see if you can see what cylinder is making the noises.
You should be able to pin point the noise better using that method. Sounds like one of more rockers are not happy.
I would also pull the valve covers and put each cylinder to TDC. while its at TDC, see if there is ANY lost motion between:
- The push rod and the rocker
- The rocker and the trunion shaft
- The rocker and the valve tip
See if you can push on the rocker where the pushrod is connected to the rocker. It SHOULD be unable to push down (collapse) If it does, you have a bad lifter. Pull UP & DOWN on the rocker where it connects to the top of the valve. There SHOULD be ZERO lost motion.
It sounds like you have a valve train issue.
Try that ad see where you stand.
Bill
When you revved it I cringed!
Get a mechanics Stethoscope or make one. ( Four foot long vacuum line, stick a small screw or metal rod into one end of the hose), put the other end into your ear, place the screw end on top of the valve cover over each valve rocker and see if you can see what cylinder is making the noises.
You should be able to pin point the noise better using that method. Sounds like one of more rockers are not happy.
I would also pull the valve covers and put each cylinder to TDC. while its at TDC, see if there is ANY lost motion between:
- The push rod and the rocker
- The rocker and the trunion shaft
- The rocker and the valve tip
See if you can push on the rocker where the pushrod is connected to the rocker. It SHOULD be unable to push down (collapse) If it does, you have a bad lifter. Pull UP & DOWN on the rocker where it connects to the top of the valve. There SHOULD be ZERO lost motion.
It sounds like you have a valve train issue.
Try that ad see where you stand.
Bill
Thread Starter
Racer
Joined: Jun 2011
Posts: 405
Likes: 5
OUCH!
When you revved it I cringed!
Get a mechanics Stethoscope or make one. ( Four foot long vacuum line, stick a small screw or metal rod into one end of the hose), put the other end into your ear, place the screw end on top of the valve cover over each valve rocker and see if you can see what cylinder is making the noises.
You should be able to pin point the noise better using that method. Sounds like one of more rockers are not happy.
I would also pull the valve covers and put each cylinder to TDC. while its at TDC, see if there is ANY lost motion between:
- The push rod and the rocker
- The rocker and the trunion shaft
- The rocker and the valve tip
See if you can push on the rocker where the pushrod is connected to the rocker. It SHOULD be unable to push down (collapse) If it does, you have a bad lifter. Pull UP & DOWN on the rocker where it connects to the top of the valve. There SHOULD be ZERO lost motion.
It sounds like you have a valve train issue.
Try that ad see where you stand.
Bill
When you revved it I cringed!
Get a mechanics Stethoscope or make one. ( Four foot long vacuum line, stick a small screw or metal rod into one end of the hose), put the other end into your ear, place the screw end on top of the valve cover over each valve rocker and see if you can see what cylinder is making the noises.
You should be able to pin point the noise better using that method. Sounds like one of more rockers are not happy.
I would also pull the valve covers and put each cylinder to TDC. while its at TDC, see if there is ANY lost motion between:
- The push rod and the rocker
- The rocker and the trunion shaft
- The rocker and the valve tip
See if you can push on the rocker where the pushrod is connected to the rocker. It SHOULD be unable to push down (collapse) If it does, you have a bad lifter. Pull UP & DOWN on the rocker where it connects to the top of the valve. There SHOULD be ZERO lost motion.
It sounds like you have a valve train issue.
Try that ad see where you stand.
Bill
I can't seem to pin point the noise using my stethoscope. I checked all the valvetrain at tdc and I can't find any movement.
Compression test revealed 110psi I'm cylinders 3 and 5. 235 in 7. The best I could guess with the stethoscope was around cylinders 3 and 5. Replaced the rocker and the pushrods on those 2 cylinders. Since it seems like I need a new head gasket on the drivers side anyway I might just pull the head and see what it looks like. But I don't want to do all that and put it together just for the noise to be bottom end related
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From: Kansas City (Lees Summit) Missouri
Thread Starter
Racer
Joined: Jun 2011
Posts: 405
Likes: 5
Pulling each plug wire didn't sound any different. It might have quieted it down just a little on cylinder 3. But I'm not sure if that is all in my head since the compression check results. I took the wire on and off at least 10 times to see if it was different