Compressor blowoff whistle?

[acme66]

When your compressor shuts off and auto releases head pressure, all the trucks I am used to (school buses mostly) pop, hiss sharply and stop. On my 923 it pops, hisses sharply then tapers off with a whistle over about 10 seconds. My gut feeling is that the pressure release is sticking, I just wanted to be sure it wasn't a normal 5ton thing before I dig into it. Tried a search and didn't see any threads.

Ken

 

[doghead]

If your referring to the sound the air governor makes after the truck is shut off, yes, that is normal.

 

[acme66]

No as you drive and the compressor brings the tanks up then kicks out. I am used to a whoosh and done not a whoosh and then a long slow whistle. Just curious if it is a normal noise as I am still learning them.

Ken

 

[rangereter]

Ken, Are you running an air dryer? At what pressure do you hear the relief occur? Where is the relief happening at, at the governor, pressure relief valve? If your governor is not sending the cutout/unload signal to the air compressor, then you would be hearing a relief valve blowing off which is louder and takes several seconds to discharge pressure below relief setting (and cycles frequently whether any air is used or not).
Regards, Bob

 

[acme66]

130psi and yea it seems to be coming from the air dryer. So it is not normal and I will be looking into it. Thanks.

Ken

 

[silverstate55]

Just rebuilt my air dryer on my M931A2; while reading through the instructions for the 6026 kit (with the large spin-on filter), it specifically says that when the dryer filter needs to be changed, it will start whistling.

In case anyone pulls this thread up when their air dryer starts whistling...