spx13

Hi guys,

long time lurker here. In some need of desperate help on my 1994 C2. It recently developed this "flapping" sort of noise from about 2-3k rpm, under moderate load. It goes away at higher rpm and does not effect drivability from what i can tell. I've disconnected all belts in order to isolate a/c, fan, alternator, etc. I've also remove primary and secondary mufflers, but the sound is still there and very hard to locate. Oil pressure is great and no smoke from tail pipe. Next step is a valve adjustment and spark plug replacement, but wanted to ask the community first. Anyone ever experience something similar?

EDIT: Thanks guys. Was a hole in the cat. Replacing this week!

txhokie4life

Does the sounds exist with clutch depressed (assuming 5 speed)

BTW, no link to video

Mike

spx13

Thanks Mike.

Sorry took me a minute to figure out the upload process. Can you see the video now?

And yes, clutch in or out, car moving or stationary, the sound doesn't change.

Michael D'Silva

When I had this old fiat when I was a kid, it used to sound like that at low rpm, but at higher rpm, it smoothed out...
Turned out it had a burned valve seat... so at low rpm, no compression... but at higher rpm, just enough for the cylinder to fire....

AOW162435

Exhaust leak?




Andreas

spx13

I suppose it could be an exhaust leak, but I've gone as far back as the primary muffler, so it would probably have to be in the heat exchangers. I looked around there and the heads, no broken studs or obvious signs of a leak.

thanks guys for the insight. Ill continue to battle this.

ras62

If you're lucky a loose plug or exhaust leak but I suspect that is a broken head stud.

txhokie4life

I listened to the video -- I'm a bit at a loss at the moment.

Exhaust leak is possible, it almost sounds like when you are "accelerating".

You could check compression and leak down for sanity purposes easy enough.

Mike

spx13

Would a broken head stud sound like this? I would think it would get louder with rpm instead of disappear? I would also think there would be other signs like smoke, leaking, or loss of power?

AVI_8

Sounds like the kind of noise you'd expect with an exhaust leak at the exhaust manifold (heat exchangers) check for a leak there.
Edited to say I just noticed that you checked there, possibly if you've a leak there it's hidden by the heat exchanger casing around the manifold? Can you get someone to rev the engine whilst you're checking where the noise is coming from below.

apanossi

Not sure about exhaust leaks, but could this be engine knock? Engine knock is audible mostly under load and acceleration. I would put engine timing and a valve adjustment high on your list of things to check.

Pasman

was following this as I had a similar sound, noticed the update that
the sound was coming from a hole in the cat. converter? If this is
true, then need to take a look at it to make sure no holes....
Cheers!