Strange Engine Noise

[nicko]

Can any of you learned folks out there identify the strange noise coming from my engine? It's not the exhaust; that's been changed.

All advice gratefully accepted.

Nico

 

[BJ8Healeys]

If the exhaust system has been changed recently, perhaps the brass nuts were not torqued enough to clamp the gaskets. This could allow them to flutter and make that noise.

 

[nicko]

The exhaust was changed maybe 4 years ago and I haven't had any problem with it. The noise slowly started about a year ago and got worse. I haven't used the car for maybe 7 months .some one has suggested it might be a gasket? Then another said it wasn't. The engine doesn't vibrate and runs smooth its just the sound?

 

[Healey Nut]

Cracked exhaust manifold or failed gasket.

 

[Michael Oritt]

Though it's impossible to be definite without being at the car, the noise certainly sounds exhaust-related. Could be a crack, a leaking exhaust gasket or the like. Then again the noise is definitely changing with RPM and though the car is stationary, a lot of parts--from engine internals to the drivetrain--could fill that bill and be on the list of suspects. I'd start poking around with a stethoscope while the engine is running which should bring you to--or closer to--the source of the noise.

 

[Bob_Spidell]

Sounds like a (bad) exhaust leak. FWIW, I haven't had much luck with the brass nuts on the manifold-downpipe studs; they always seemed to work loose (yes, I used new ones). I finally solved that issue by double-nutting with steel nuts and anti-seize on the studs to prevent them corroding together. If it's the gaskets on those flanges, you'll usually see some black soot at the point of failure (or anywhere else on the exhaust, for that matter).

Check all around the external moving parts. If, for instance, your engine mounts collapsed--they're known to sag pretty bad--the fan or even the crank pulley could be hitting something (but that would probably sound more metallic).

 

[Gliderman8]

Could your exhaust pipe be blocked? You said the car sat for 7 months. Maybe a rodent nest in pipe?

 

[Bob_Spidell]

Could your exhaust pipe be blocked? You said the car sat for 7 months. Maybe a rodent nest in pipe?

Good thought. My dad bought a 60s-era Thunderbird that wouldn't run right, and eventually found a blocked exhaust (I forget what was in there, dead rat maybe). If the exhaust is blocked, the engine won't rev worth a hoot.