CAT 518 compressed air

[JudgeC]

I have an '84 CAT 518 grapple skidder. There is a lot of compressed air coming out of a nipple in the air dryer (I assume it's a drain and I can't get pressure to build so the parking brake will release. Any ideas?

[Bill Saf]

 the air dryer has no full time drain. when the air pressure comes up to 120psi you should hear what sounds like a sneeze. the big hole in the bottom of dryer is where the dryer expels water or oil if oil comes out your compresser is bad. do you have any pics of dryer? it would help it give you better info.

Bill

[goober]

we had that a lot on trucks.  we had  hose on the dryer and we bent it over till the valve would seat.  some times we would put a thumb in the hose till it stopped.  hope that helps.

[snowstorm]

try a new governor on the compressor first. they are cheap and can cause problems. if its a bendix compressor the gov is under $20 

[mills]

I had to change the compressor out on my 518. Believe it or not, but CAT was a couple a hundred dollars cheaper than anywhere else I could find.

[s grinder]

Could be the purge valve stuck open in the air dryer, causing air to constantly come out of [large opening].Before you go and spend a lot of money , get a double male fitting and by pass the air dryer,if you build up you know thats the problem.

[JudgeC]

I installed a new governor and bypassed the dryer. The parking brake releases properly.
I'm trying to find a seal kit for the dryer- No luck so far. It's called an aerofiner II

[snowstorm]

now hook the air dryer back up and see if all is ok. most of the time air compressor trouble starts at the governor