Hissing sound and exhaust smell under the engine?

[Interceptor]

The main suspect is the exhaust header gasket - can it be something else? Can the bad exhaust header gasket cause power loss and hesitation?

[tim]

I just fixed a friend's that had a similar issue. It wasn't the exhaust manifold but rather a rubber boot that connects to the block and has a return hose up to the top of the intake. I think it's the pcv return, or at least it performs a similar function. It had a crack in the underside near where it exited the block and made a hissing sort of noise whenever you stepped on the gas. I duct taped it until the bma package arrived, and r&r'ed it. Hope that's it. If you had a cracked manifold you'd hear it!, and if it's the gasket, and you're getting an air noise, it would be one big gasket failure (which would be easy to see I think).

[Bill R.]

power loss and hesitation its a bad catalytic converter which has melted and fused internally or broken up internally and formed a plug in the pipe which accounts for the hissing sound.. its exhaust squeezing out of the closed up pipe... but on most of them if this is the problem you will have almost no power at the higher rpm's

The main suspect is the exhaust header gasket - can it be something else? Can the bad exhaust header gasket cause power loss and hesitation?

[Interceptor]

power loss and hesitation its a bad catalytic converter which has melted and fused internally or broken up internally and formed a plug in the pipe which accounts for the hissing sound.. its exhaust squeezing out of the closed up pipe... but on most of them if this is the problem you will have almost no power at the higher rpm's

Higher rpms are fine, the lower ones are the problem

I must admit, a few months ago, when I was coming down off a very high curb I heard a scratching metal noise. Later I discovered that my exhaust carrier was bent - the one between the front silencer and the rear muffler. Could that have caused gaskets to fail?

Btw., my car passed the emissions testing with flying colors after that!

[Interceptor]

I just fixed a friend's that had a similar issue. It wasn't the exhaust manifold but rather a rubber boot that connects to the block and has a return hose up to the top of the intake. I think it's the pcv return, or at least it performs a similar function. It had a crack in the underside near where it exited the block and made a hissing sort of noise whenever you stepped on the gas. I duct taped it until the bma package arrived, and r&r'ed it. Hope that's it. If you had a cracked manifold you'd hear it!, and if it's the gasket, and you're getting an air noise, it would be one big gasket failure (which would be easy to see I think).

I recently started changing all the rubber boots and hoses - I've changed all of them except the ones that require me to remove the intake manifold. I'm waiting for my intake manifold gasket to arrive so that I can continue with the work.

[tim]

Say, did any of those hoses have any backflow prevention valves on them by chance. There was a recent poster who accidentally replaced one backwards on the pcv on the small block m60. Anyway, you may want to check out Bill's suggestion . I guess if he's right, you should have noticeably less exhaust pressure.

[632 Regal]

check exhaust closely, if it was gaskets it would leak and you would definetly have popping sounds