Author Topic: not building air pressure  (Read 609 times)

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Offline Charlie/Susie

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not building air pressure
« on: March 16, 2020, 04:45:27 PM »
hello again, problem # 547 . had coach stored for less then a month. It has auto suspension and I left it on lower for that time then I went and started flipped the lever to auto but the low pressure buzzer kept going and no pressure was building. Reved engine but no good. Shut engine down, flipped lever back and forth then restarted eng. Still no pressure, any ideas? 2005 Fleetwood Bounder, Cummings 5.9 300hp. Thanks Charlie.
Charlie and Susie
2005 Fleetwood Bounder 38N 5.9 cummins
2014 Corolla toad

Offline Brett Wolfe

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Re: not building air pressure
« Reply #1 on: March 16, 2020, 06:21:34 PM »
Have you walked around the coach to listen for an air leak when this happened?

Don't know what chassis you have-- do you have an air dryer?  If so, is there air exhausting below it when this happens?

If neither of the above, one of the least expensive parts of the air system is the AIR GOVERNOR.  Under $25. It "turns on/off" the air compressor.

Offline David.e.atherton

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Re: not building air pressure
« Reply #2 on: March 16, 2020, 10:01:21 PM »
Gentlemen, not building air can come from 3 areas. First check the discharge unloaded valve on bottom of air
dryer  ( valve stuck open  ), second area there is a check valve between the wet air tank and dry tank that
opens at 90 psi and if stuck will not build air. Note in many cases the wet and dry air tank are a one air tank
that is split to operate wet tank first than open check valve passes air pressure to dry side tank. Third area
of problem from sitting in the unloaded valve on top of the air compressor that is stuck from sitting. If you have a older style air compressor the unloader valve is located behind the air compressor air filter and get at by
removing two 1/4 inch bolts. Ask Dave, Dave Atherton Retired Cat Mechanic

Offline Douglas Klink

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Re: not building air pressure
« Reply #3 on: March 17, 2020, 05:00:09 AM »
In my case, 2006 Beaver Patriot Thunder, I discovered that the braided hose from the air compressor to the air dryer had been rubbing on one of the tranny cooler lines above the transmission and a small hole had developed.  The air line was too long and had an upward kink in it that caused the rubbing.  I replaced that like with an 8" shorter like to remove the kink and all was well.  That link also would have kept moisture from running downhill to the air dryer as it is supposed to, that like should have a constant slope downward from compressor to dryer.  Bus wouldn't build pressure unless it was above 1300 rpm and you couldn't hear the leak when the engine was running.

Offline David.e.atherton

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Re: not building air pressure
« Reply #4 on: March 17, 2020, 05:54:06 AM »
Douglas, that is a very good thought and very hard to pin point. We had two air system problems with the
steel braid hose coming from air compressor pin hole leak inside of clamp on frame. Very hard to find on
the first one we worked on and were little smarter on the second steel braided hose and root cause on
both wearing movement inside of clamp along frame. Ask Dave, Dave Atherton Retired Cat Mechanic

Offline Charlie/Susie

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Re: not building air pressure
« Reply #5 on: March 21, 2020, 02:21:31 PM »
Thank you gentlemen, the air dryer was leaking and it was the original unit with the install date painted on of '04. It is a haldex so I just replaced the entire unit, $685.00. I guess it should last another 15 years. It is on a f/l xc chassis. Thanks again for the many responses.
Charlie and Susie
2005 Fleetwood Bounder 38N 5.9 cummins
2014 Corolla toad

Offline Brett Wolfe

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Re: not building air pressure
« Reply #6 on: March 21, 2020, 02:25:51 PM »
Two points:

Air dryers should be serviced every 3-4 years.  If one fails, one of the failure modes is that the desiccant comes apart and contaminates the whole air system-- air brakes and suspension components.  Think white powder in every one of those small valves/orifices/etc.

And a factory reman (factory that makes it-- Haldex in your case) is a very good and cost effective alternative to new.

Assume/sure hope the $685 included a LOT of labor!