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Topic: Air Dryer (Read 531 times) previous topic - next topic

Air Dryer

My air dryer is cycling every 30 seconds and purging out the bottom. Takes about 8 to 10 seconds to seal itself off and than blows out on to the ground under the engine in 30 seconds.
Running the engine and pumped down the brakes to 90 psi and the pressure builds back to 125 and blows out and holds the 125psi while idling.
I bled the rear air tank and little to no moisture in the system.
Comments
Criticism
Concerns I need to be aware of?
Paul R.
1998 U270 36'

Re: Air Dryer

Reply #1 –
Time to rebuild or replace with a remanufactured.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Air Dryer

Reply #2 –
As Doug says above.  The check valve in the dryer has gone bad.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Air Dryer

Reply #3 –
I think it's time to have your air dryer serviced.
Alan Fink
Waupun, WI
2000 Blue Bird Wanderlodge  LX40
2018 F150 4x4
2020 Jeep Wrangler Unlimited  Rubicon JL

Re: Air Dryer

Reply #4 –
I replaced ours with a spin on. Cheap and only took a minute to change the last time. You do have to build a bracket and change the 12V wire but pretty easy.


Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Air Dryer

Reply #5 –
Quote from: paul r –
My air dryer is cycling every 30 seconds and purging out the bottom. Takes about 8 to 10 seconds to seal itself off and than blows out on to the ground under the engine in 30 seconds.
Running the engine and pumped down the brakes to 90 psi and the pressure builds back to 125 and blows out and holds the 125psi while idling.
I bled the rear air tank and little to no moisture in the system.
Comments
Criticism
Concerns I need to be aware of?

A resource that may be helpful to you. Sounds like it's time for a rebuild.
2008 Nimbus 342
Build# 6464
ISM 500
Allison 4000 w/retarder
2021 Jeep Grand Cherokee

Re: Air Dryer

Reply #6 –
Same symptoms on mine last year. Rebuilt unit took care of it. I swear the replacement looked new not rebuilt. Jim.
Jim and Dona
2002 U295 36'
Lily, blue healer. Our fury person
Manx mid travel Ecotec turbo
2022 Bronco badlands Sasquatch
Trail 90 and 110cc

Re: Air Dryer

Reply #7 –
Replaced with remanufacture air dryer, replaced Governor, replaced check vale on wet tank, soapy water test ( found no bubbles ) at 100 psi. Listen for sound ( no hissing ).
PSI holds steady at 135 psi with engine on while Bus is stationary. Air dryer purge is about every 60 seconds. Could this be caused by air issues in the Bendix braking system behind one of the wheels?
Is the Gus the Bus safe from damage? I am leaving Michigan to drive south to Ft. Myers, Fl to begin cleaning up damaged property after Hurricane Milton and will be dependent on the bus for everything once I get there.
Paul R.
1998 U270 36'

Re: Air Dryer

Reply #8 –
The guage should show the cycle.  Imho.
Drop to 110 cut in , and up to 135 cutoff?
The purge cycle is a little fast. For me.  But as long as the compressor can keep up your travel should be uneventful. 
 But it's clear to me that you have a small issue between the dryer and compressor    . Maybe as simple as a hose leak or check valve.
The brakes have a high pressure line near the axles and a brake relay valve close to the chambers. Pushing the brake pedal activated the relay valve and chambers .

You can sorta test the system by applying the brakes and watching the air pressure.  It will fall rapidly and should stabilize at a lower reading. Some leaks may show up and there are miles of hoses to fault.
A very slow leak is tolerable , but a hissy  leak is not .

Re: Air Dryer

Reply #9 –
Quote from: paul r –

PSI holds steady at 135 psi with engine on while Bus is stationary. Air dryer purge is about every 60 seconds.

Purging air every 60 seconds your compressor is working overtime if no air is being used. If no air leaks are found especially between governor and air dryer try a new governor set to 120psi, cheapest place to start.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Air Dryer

Reply #10 –
The purge line might be connected to the wrong port .  It should be inline with the unloader valve slider .