AIR DRYER AIR DISCHARGE...how many times is to many times.

Firs question is how old is the "air system"? If the compressor, air dryer have 500,000 on them or 5 years just do yourself a favor and replace compressor, governor, air dryer, and the small airlines from governor to tank and air dryer. They do not last for ever. The excess oil from an old compressor just crud's up the air dryer. When we had this over cycling on our old trucks it was always the dryer. Then people will tell you to just buy the valve on the bottom. Just spend $220 and get a reman. bendix from fleetpride. The reman. compressor is the best insurance to keep all the metal out of your engine when it detonates. Your whole issue is just between the governor and the dryer.

 

Last fall I replaced the dessicant cartridge and purge valve in my AD9. When it was back together, the truck built air fine, but the air dryer would spit every 15 seconds as you describe, despite the pressure on the dash barely dropping. Somehow, I messed up the O-rings sealing the new purge valve; replacing them solved my particular problem. Just a thought.

 

Check the unloader valve on the compressor, check the purge valve on air dryer , and check for air leaks in the line between the compressor and the governor valve

 

wasting time with engine running disconect discharge off compressor make up fittings to conect workshop air an get out the soap water cotton covered braided the worst offender but high cycling speed surgests unloader orings high mileage compressoors head should be removed an valve kit installed as this is primary cause of comp failures cheers mark

 

gov valve only turn compreesor on and off plus second linefrom between mounting bolts go;s to dryer if the unloader orings are shot the swiching air escaps to compressor in let lowers wet tank pressure to comp cut in point builds up air blows off leaks out so on and so on----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- !

 

just found this, good info THX

my volvo d12 just started doing the same thing yesterday

 

In 17 years I have replaced the gov 4 or 5 times. Less than $20 so it is a good place to start and if it wasn't the culprit you are good to have a spare under the bunk anyway.

 

fan hub leaking, can't hear it with engine running, and does not leak when shut off.