I have a 1985 Monte Carlo & I am experiencing "air swooshing" noise on the Passenger Side of the car, in an area at the Firewall behind the dash, while the car is under acceleration. It slows as you slow, but also continues in some cases at stop & idle. Could this be a bad vaccuum line. Open to any suggestions - car runs like honey on a hot summer day otherwise.

Thanks

 

Im no expert and it could be vacuum but I would check the belt/pulley assembly.

 

I don't know what that means.

If you have a V6 or V8 and you still have the A.I.R. (aka smog pump) system, the sound you're describing is consistant with a failed diverter valve muffler or diverter valve assembly. If that's the case, one or both may need to be replaced.

By the way, the most obvious symptom of a vacuum leak is a sporadic gurgling or popping sound from the exhaust during deceleration, like when parked, you rev the engine up to about 3500 RPM then let off the gas pedal and listen to the exhaust. However, even if you don't hear that noise, you could still have a subtle leak like from the vacuum advance on the distributor. Not to be confusing but a small leak like from the distributor would not make the sound you're describing.

A non-invasive way to track down a vacuum leak is to use a propane torch — NOT lit, of course. You see, a vacuum leak draws regular air into your intake system creating a lean fuel-air mixture. Open the propane torch valve just enough to allow a low flow of propane then put the torch nozzle next to places like a hose connection. If there's a leak, it will draw propane into your intake system making it a little richer and raising the RPM a little.

Good luck and keep us updated.

 

Corrected..."like honey on a hot summer day". I'm interested by your suggestion of the failed diverter valve, however this sounds very much like it is coming from the inside of the car, near the blower motor area of the AC, behind the dash @ the firewall. I have audio of it, just need to figure out a way to upload.

Thanks