engine noises again...

[Chris500]

What could it be: tipping noise (playcard on a spinning bicycle wheel) from the cylinder bank/drivers side on my '96 Griff with 36k miles. other than the typical blown manifold gaskets tipping the noise comes in when engine warms up. Worst in high gear/low rev. I already had the left manifold out, welding some smaller cracks, new gaskets, all tightend up properly. Did not help.
is it possible that the manifold cracked inside where the four pipes are leading into the one? No loss in power sensed. Someone has a clue? Thx Chris

[GreenV8S]

Chris500 said:

is it possible that the manifold cracked inside where the four pipes are leading into the one?

Very possible, it's a very common failure and not easy to spot unless you're looking for it.

[Chris500]

that means I would have to cup the pipe open... Before going this way which will end up installing a new manifold, what else could it be? My feeling is that the noise rather comes from above the manifold, from the drivers side cylinder head.

[Ballistic Banana]

I would be looking at all hoses, leccy stuff too( they can make ticking sounds), get a large screwdriver and cup your ear to the handle end and put the other around the area you think it may be. If it's at the part where the 4 go into 1 on the manifold you should still be able to see /feel it, perhaps use a little mirror, or once cool push a rag down there and see of any exhaust dirt comes off on it.

HTH

BB

[Chris500]

thx for your support.

[APMAUTO]

just a quick tip remove the manifold and fill with water any leaks will be seen straight away

[Chris500]

APMAUTO said:

just a quick tip remove the manifold and fill with water any leaks will be seen straight away

we had welded the smallest crack in the manifold and put it all together with new gaskets. Thats why I assume the manifold could be cracked inside where the four pipes coming together, invisible from the outside. Where to shop for a new manifold?

[Boosted LS1]

Does it do it when the car's idling or only when driving underload? If only when driving then I'd make sure it's not detonation or anything unpleasant. It could just be the header though

[Chris500]

Boosted LS1 said:

Does it do it when the car's idling or only when driving underload? If only when driving then I'd make sure it's not detonation or anything unpleasant. It could just be the header though

noise when
idling: slightly when engine cold, louder when warmed up
driving: noisy under load. Getting quiet again over 4k rpm.

[macdeb]

There is an easier way to find if the manifold is leaking as posted up here before by my old [ahem] mate Bobfather/tvrbob. [tongue firmly in cheek] Anyway, credit where due.
Blank off one exhaust pipe and send compressed air into the other, squirt soapy water over exhaust manifolds etc and see if bubbles produced, if so then there is the leak. Brilliant, just wish I'd thought of it.

[v8 racing]

Chris500 said:

Boosted LS1 said:

Does it do it when the car's idling or only when driving underload? If only when driving then I'd make sure it's not detonation or anything unpleasant. It could just be the header though

noise when
idling: slightly when engine cold, louder when warmed up
driving: noisy under load. Getting quiet again over 4k rpm.

Just a general rule if it is an exhaust blow it will generally get quieter as the engine warms up, basically the exhaust expands and seals small cracks, try pulling a plug lead of at a time to see if the noise goes away, i dont want to worry you but if it gets louder as the engine warms up it could well be a worn little end in the piston Rob

[chris52]

macdeb]There is an easier way to find if the manifold is leaking as posted up here before by my old [ahem] mate Bobfather/tvrbob. [tongue firmly in cheek said:

Anyway, credit where due.
Blank off one exhaust pipe and send compressed air into the other, squirt soapy water over exhaust manifolds etc and see if bubbles produced, if so then there is the leak. Brilliant, just wish I'd thought of it.

correct me if I'm wrong but wont there be exhaust valves open? and if so isn't it possible to then blow any brocken bits of cat/ crap straight into the cylinder block. Like i say I may be completley wrong here just thinking out loud.

Chris

Edited by chris52 on Wednesday 15th July 20:40

[macdeb]

chris52 said:

macdeb]There is an easier way to find if the manifold is leaking as posted up here before by my old [ahem] mate Bobfather/tvrbob. [tongue firmly in cheek said:

Anyway, credit where due.
Blank off one exhaust pipe and send compressed air into the other, squirt soapy water over exhaust manifolds etc and see if bubbles produced, if so then there is the leak. Brilliant, just wish I'd thought of it.

correct me if I'm wrong but wont there be exaust valves open? and if so isn't it possible to then blow any brocken bits of cat/ crap straight into the cylinder block. Like i say I may be completley wrong here just thinking out loud.

Chris

Well, dunno, s'pose many know more on here but can't see crap being blown back in as only low pressure air used, perhaps should've said a rag up exhaust not blanked off, anyway the rate valves move when running I can't see that there will be bits just waiting to drop off at standstill.
Have used method myself to find a very frustrating leak on exhaust flanges.
edited for spelling errors, nothing at all to do with beer. hic'.

Edited by macdeb on Wednesday 15th July 20:43

Edited by macdeb on Wednesday 15th July 20:45

[Chris500]

thank you for the response. Very helpfull comments. I'll keep you posted.