I have a 305 tpi and when ever I turn it off the engine and it begins to slow down rotation it makes this weird sound like a wheezing, or that sound when you let air out of a balloon slowly. I thought it was low on oil but the oil is full. Is this common on all old firebirds? I have a 305 with about 44k miles on it. I recently replaced the transmission and the fluid in that is also full.

 

Is it possible you have a coolant leak in a radiator hose that you only hear after turning off the motor? How you describe it, sounds like some kind of pressure leak somewhere. Maybe water pump bleeding pressure through the shaft seal? I have heard that sound before over the years from a couple of cars. Never knew what it was.

 

Well the cooling system is all new except the water pump. It doesn't seem to lose water either. It started happening within the past 3-5 months. I thought something on the serp belt is starting to seize. But there is no sound when the engine is running that I can hear. I'm just hoping nothing is wrong with either the trans or engine.

 

Is this an A/C car by chance?

 

my 90 vette used to do that. just a random cylinder on a intake cycle drawing air in.

 

Yes it has a/c. It has been converted to r134a. The a/c works but is empty at the moment.

 

I get a sound similar to that. For mine I believe it is the fuel pressure in the return side of the line bleeding off into the tank. It's almost like the FP is still running for a few seconds ( maybe the OP switch is keeping it on??).