Loud Exhaust but only when Hot after highway run – Has me Baffled

keitho64 · keitho64's Garage

Here is an odd problem for you Pelicans. My 911 with a 2.7, early headers / exhaust and webers gets very loud after driving on the highway for a while. If the car is cold or city driving it sounds normal. Even if I drive for an hour plus in city traffic or below 3,000 it sounds normal. However after 5 to 10 miles of running at 3,500+ it gets real loud. It is almost as if the baffling in the exhaust is shot. When I let the car cool and restart it, it sounds normal again.

I plan to check all bolts tomorrow but a visual inspection shows no loose bolts, nor can I see any holes on the headers or muffler. I will also add that I cannot hear any signs of an exhaust leak. Is it possible for the baffling in the muffler to be bad? The muffler is an early style dual inlet, single outlet.

Thanks

carrera turbo · 10-12-2008, 08:01 PM

check to see if the tail pipe is distorting with heat and rubbing the body causing a matting surface to open up. and being a 2.7 do you here a Hssss Hssss as you crank it. i just inspected a budys car pulling head studs that he says is quite

when cold and load when hot. allthough ive only heard it hot, and sounds really bad.

maybe theres a broken baffle. try hitting the bottom of the muffler with a rubber mallet after its up to temp and see if theres anything loose.

these are all guesses

thanks ed

keitho64 · keitho64's Garage

I was somewhat afraid of a head stud ... I will check the baffle by hitting the muffler and all the bolts tomorrow. If I do not find anything there I guess I will check the head studs for torque. I will pay attention when I start it and see if there is any hissing sound.

Is it possible for a head stud to be pulling out, the engine making all the noise, but no signs of power loss?

keitho64 · keitho64's Garage

OK, nothing major one of the air injection plugs was backing out.

jevvy · 07:13 AM

I used to get this in my old 8V golf GTI - having experienced the same thing in a few gti's I put it down to my ears being at fault not the car. After a highway blat in a car with a loud exhaust I think it just takes your ears a while to get back to normal and they seem to pick up on the boomyness of the exhaust until they do.

Maybe get a mate to take it up the highway and you wait and get back in once its back and see if you get the same feeling?