what’s up rawze and all the other fellow forum junkies I have an issue that’s is really starting to get under my skin I own a 2011 prostar premium with an isx 435 recently I noticed the purge valve was hissing way to long so I decided to go ahead and replace the dryer,purge valve and governor everything works fine can’t complain but I noticed once I build pressure I slowly lose pressure until about 100 psi and the compressor than kicks on and build it back up I have looked high and low and can’t find the leak I changed all the fittings to brass on the air dryer assembly and I changed my air compressors main line to brass also and still leaking out somebody anybody pls pls pls help me I just wanna see my truck sit at 135 psi and only lose air when I apply the brakes not just for no reason...!!! Thanks fellas
I remember reading a post by Rawze about Prostar common wiring issues and air leak locations. But a quick look and I wasn't able to find it.
This forum can only give you those common spots. You need a spray bottle of soapy water.
I’ve been spraying it with soapy water for three days I appreciate the sarcasm tho lol
Alot if times it's not one leak, but a combination of small ones that cause this.
I don't care for those plastic air fittings. I've got one of those and another levelling valve to replace when I get home, because it only leaks down when loaded and you can only just barely hear it with the truck off. Also had another leak that required me to air up, block the wheels and release the brakes to find it.
I've been considering replacing alot of my nylon lines with copper and compression fittings, to eliminate alot of potential leak sites under the truck. I can still use nylon where I need additional flexibility.
(04-04-2018 )Pmarrero88 Wrote: [ -> ] what’s up rawze and all the other fellow forum junkies I have an issue that’s is really starting to get under my skin I own a 2011 prostar premium with an isx 435 recently I noticed the purge valve was hissing way to long so I decided to go ahead and replace the dryer,purge valve and governor everything works fine can’t complain but I noticed once I build pressure I slowly lose pressure until about 100 psi and the compressor than kicks on and build it back up I have looked high and low and can’t find the leak I changed all the fittings to brass on the air dryer assembly and I changed my air compressors main line to brass also and still leaking out somebody anybody pls pls pls help me I just wanna see my truck sit at 135 psi and only lose air when I apply the brakes not just for no reason...!!! Thanks fellas
If you only loosing pressure when you apply your brakes maybe you have a leaking brake chamber or a hose leaking when you push on your brakes, plus this prostars are known for loosing air pressure hopefully you find your problem
There is a box of pnuematic relays in the frame rail that love to leak. There are o-rings between each one. Those love to leak you'll find it between the transmission and frame rail on the drivers side.
Also spray the top and bottom of your air bags. Dry rot around the base will leak ultra slow and inaudible then multiply that by 4-6 bags if you have steer air bags and include the cab air bags too and it turns into a pretty bad leak.
Almost all my fittings are brass at this point we got it down to two guesses foot valve and the front brake valve I’m holding better air in my secondary only losing about 5 psi it’s the primary now that’s leaking down....
A couple airlines that are hard to check for air leaks are the signal lines from the air governor to the air dryer or the signal line from the primary tank to the air dryer. Start the truck up and JUST BEFORE the air governor kicks in @120-130 psi shut the truck off and listen for air leaks. Sometimes you have to have a second person under the truck ready to listen when you have the truck shut off or you have to shut the key off and quickly go underneath the truck to catch the leak before the line leaks out. You have to catch it before the dryer purges.