Skip to main content ↑ ↓
Topic: Air pressure leak (Read 343 times) previous topic - next topic

Air pressure leak

On the road, far from home. In a Walmart parking lot we're having a problem with the air suspension. Dashboard gauges are showing 65-70 lbs pressure with the engine running, and will go up no further.
Parked for an hour with the engine off, the gauges dropped to 57-60 lbs and hold steady at that level.
Starting the engine again the pressure increases slowly but will not go beyond 68-70 pounds. Air hiss can be heard near the right rear wheel well. Upon stopping the engine the hiss continues for 5 seconds or so then stops.
With engine running I can lift the front of the coach all the way with HWH system and it stays up. Cannot lift the rear at all.
What does everybody think?

Update: I just found this. Air is ejecting strongly from the bottom of this square box, attached to the retarder accumulator. I assume that is not supposed to be happening?
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C

Re: Air pressure leak

Reply #1 –
Could be a bad valve in the AIR DRYER.

Can you confirm that the air is coming out the bottom of the air dryer?

And, when was the air dryer last replaced/serviced?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Air pressure leak

Reply #2 –
Quote from: Dan & Annie –
Air hiss can be heard near the right rear wheel well.

This area you could have a bad ride height valve or the linkage has came off.
Hole in air bag
Cut air line to 6 pack that is located in that area.
Check the air line to the retarder accumulator actuator valve.

Mike


Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air pressure leak

Reply #3 –
Quote from: wolfe10 –
Could be a bad valve in the AIR DRYER.
Can you confirm that the air is coming out the bottom of the air dryer?
And, when was the air dryer last replaced/serviced?
Out the bottom of the dryer and into the wet tank? Or through a pressure relief valve, or?
I can turn the remote drain valve for the wet tank and see that it is pressurized.
I've owned the coach for 2 years and have no idea when the dryer might have been serviced or replaced.
Also when I "DUMP" the airbags completely through the HWH, I can feel both front and rear air bags are empty - very soft. Restarting the engine refills the front bags and the HWH can then lift the front all the way up. The rear bags only inflate slightly, still feel just a bit soft, and no increase in pressure from the HWH.
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C

Re: Air pressure leak

Reply #4 –
With the engine running, reach under the back and see if air is purging from the bottom of the air dryer.

Should be no leak from any tank, unless the drain valve is bad OR there is a hole in the tank.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Air pressure leak

Reply #5 –
Dan,

Where are you located?  There may be a member that is close by that may be able to help hunt for an air leak.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air pressure leak

Reply #6 –
See my update to original post (couldn't figure out how to add a photo to a new reply.)
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C

Re: Air pressure leak

Reply #7 –
Quote from: Dan & Annie –
See my update to original post (couldn't figure out how to add a photo to a new reply.)

Yup, your "update" succeeds all previous comments.

Those with retarder control experience will be able to assist you.

Stay tuned.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Air pressure leak

Reply #8 –
If that is where the air is coming from that is the air valve to retarder accumulator. It could be a bug has gotten up in the drain port and got squished not letting the valve close.  You can unhook the supply air line and plug it (get a plug from a parts store) or crimp off the air line with a pair of vice grips. Now the retarder won't work till you can either get the valve cleaned out or replace the valve. I have posted an how to clean in a thread an I will hunt that thread up for you to look at to see what it is to cleaning it up.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air pressure leak

Reply #9 –
Here is the thread for you to look over.
Allison retarder air valve

Mike

One other thought is have you turned off the retarder switch that is on the console?  If not turn it off and see if the leak stops then report back.
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Air pressure leak

Reply #10 –
Good news! The problem was that valve entering the retarder accumulator was stuck open, exhausting air full time. I pulled the supply hose and plugged it. Can't use the retarder until I pull the valve, clean it and reinstall, but for now we're back in business and ready to roll!
Thanks, All.
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C
 

Re: Air pressure leak

Reply #11 –
That is good news. Have safe travels.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."