Skip to main content ↑ ↓
Topic: Air pressure drain while driving (Read 512 times) previous topic - next topic

Air pressure drain while driving

Given that I just had my foot valve replaced and last season it was the ABS valve and have always had my air tanks drain off quickly since buying the coach.

So I have a question for the group. Baring any glaring leaks. How much does everyone's air tank bleed off pressure when driving down the road? With the fairly soft suspension of the U320 and 8 airbags. How quickly will the air suspension draw down the air pressure. I drove down the road for about 10 minutes and lost about 5PSI and a bit faster on a rougher side road. I would like to have a ball park range of what folks lose and how quickly

Jerry & Nona and Kimeru the cat that thinks she's a dog
1998 36' WTFE U320  #5314 Motorcade #17711
USAF 1975-1995
2019 Subaru Crosstrek 'toad'
2003 Subaru Legacy touring car
jerry Fincher | Flickr

Re: Air pressure drain while driving

Reply #2 –
I would say what you are experiencing in air loss is quite normal. Seems like mine does about the same. Air bags are always compensating for road conditions.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Air pressure drain while driving

Reply #3 –
Thanks guys. I figured I might be in the ballpark.  I hope it stays that way.

Next project is to get my retarder working reliably. Right now it will work and then stop working and will not come back on until I stop and turn the coach off. Thus resetting the system.
Jerry & Nona and Kimeru the cat that thinks she's a dog
1998 36' WTFE U320  #5314 Motorcade #17711
USAF 1975-1995
2019 Subaru Crosstrek 'toad'
2003 Subaru Legacy touring car
jerry Fincher | Flickr

Re: Air pressure drain while driving

Reply #4 –
Quote from: bigdog –

Next project is to get my retarder working reliably. Right now it will work and then stop working and will not come back on until I stop and turn the coach off. Thus resetting the system.

May want to pull the codes on Allison before you turn it off, see if anything comes up.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Air pressure drain while driving

Reply #5 –
Quote from: Doug W. –
May want to pull the codes on Allison before you turn it off, see if anything comes up.
You press the up and down arrows at the same time while running in neutral, Correct?
Jerry & Nona and Kimeru the cat that thinks she's a dog
1998 36' WTFE U320  #5314 Motorcade #17711
USAF 1975-1995
2019 Subaru Crosstrek 'toad'
2003 Subaru Legacy touring car
jerry Fincher | Flickr

Re: Air pressure drain while driving

Reply #6 –
Quote from: bigdog –
You press the up and down arrows at the same time while running in neutral, Correct?

Yes pressing both arrows down twice will bring up codes than press mode button for d1 thru d4 codes. Holding the mode button down until you hear a beep will clear codes.
Pressing both arrows once will bring up oil level while at idle and level.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Air pressure drain while driving

Reply #7 –
And, the engine does NOT need to be running to check for codes.  Ignition on is all you need.

Yes, to check transmission fluid level the transmission needs to be warm (like 50 highway miles) and engine running.  To check, with transmission in neutral just press the up and down arrows at the same time ONCE.
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 drain while driving

Reply #8 –
Thanks Doug & Brett. Downloaded the code chart to my laptop. So when it goofs up on our trip tomorrow I'll stop and write it down.   
Jerry & Nona and Kimeru the cat that thinks she's a dog
1998 36' WTFE U320  #5314 Motorcade #17711
USAF 1975-1995
2019 Subaru Crosstrek 'toad'
2003 Subaru Legacy touring car
jerry Fincher | Flickr

Re: Air pressure drain while driving

Reply #9 –
I've never really put a timer on it but I would guess that in normal driving my air pressure goes down about every 15 minutes or so and then the compressor builds it back up. I think it's normal operation.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Air pressure drain while driving

Reply #10 –
Quote from: D.J. Osborn –
I've never really put a timer on it but I would guess that in normal driving my air pressure goes down about every 15 minutes or so and then the compressor builds it back up. I think it's normal operation.


Yup, normal.

And air is used more/cycles more frequently on rough roads and when using service brakes.  Again, perfectly normal.
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