Greetings one and all!

My rebuilt 86 RX-7 drives great, and in AZ even the AC blows cold. However every now and then, especially in the morning there is an intermittent growling noise that seems to occur mostly at idle or when the car is shut off. It will growl and groan steadily for about 10 seconds then go away. This happens about 2-3 times during my 15 minute commute.

Like I mentioned the car is seeming to work well, just leery of an impending failure of some sort.

Thanks for any suggestions or help.
-Matt

 

What area of the engine is the noise coming from?
My radiator cap on my s4 started making a hissing noise, I think it was starting to not hold pressure.

 

maYbe a recording of the sound and a location will help tremendously

 

My heat shields will make metallic groaning noises when I shut the car off.

 

This morning while driving and the groaning started I punched off the AC, and the groaning quickly stopped. This was while idling at a stop sign. Then I put the AC back on, and it quickly started making noise again.

Then, at the next stop when it was groaning I stepped on the gas while out of gear, and the groaning went away at 2000 rpm and above.

So now is it the compressor for the AC making the noise at Idle, and if so what does that mean? Like I said the AC blows cold and appears to work just fine.

Thanks guys!
-Matt

 

maybe the pump isn't lubricated well enough (possible if the system was apart and then re-charged), or a bearing on the pump is going