P.J.

I have recently noticed a hissing type sound with the S when I put my foot down, nearly like a leak of some sort. The only thing I changed recently was to put the Cat back in the car for MOT. I have checked and it is sealed perfectly.

Any idea what would make this sound under acceleration? Bit odd...help appreciated.

Thanks.

simonix

Have you checked all your hoses in the engine bay (vacuum pipes, etc)?

Daytona-Dave

if it's only started after refitting the cat, I would Check the Flange at the front of the cat first, then it could possibly be a partially blocked cat creating too much back pressure, some cats degrade after being removed from the car and left in garage's (more so cold damp one's) and get all furry like in the monolith restricting gas flow,

P.J.

I am pretty sure the seals are all ok, I fitted a new gasket on the exhaust side etc.

I also inspected the CAT before it went back on and it looked ok to the naked eye anyway, could see down through the mesh and out the other side.

If it has gathered some "fur" would a good "hoking" maybe clear it out/free it up?

Thanks

NineBolts

I know that when I've changed manifolds I've noticed some hiss which seems to come from under the car. The OEM item being heavier gauge steel doesn't have the same ring to it that the thinner lighter aftermarket manifolds do.