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Front air tank pressure

What would cause the front air tank reservoir to suddenly lose 30-40 psig. and the return to normal pressure?
Probably would not have notice, except it activated the alarm once.
Is there a overpressure safety?
The air pressure in the rear tank stays constant.
This will happen while cruising at 50-60 mph and no usage of the brakes or retarder.
Thanks in advanced for any ideas.
'02 U295 36'
Build #5937

 SKP#104358
Motorcade#17428

Re: Front air tank pressure

Reply #1 –
If you don't mind, Tom, I'd like to piggy-back a related question about the front air in my coach. 

When my 2002 U270 first builds up air pressure, the front tank really seems to lag begind the rear as they fill.  I just wonder if this is a related issue.  I frankly don't really understand why there are separate tanks.
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)

Re: Front air tank pressure

Reply #2 –
The whole reason is for safety. One tank supplies front brakes and other the rear ones etc. If there is a big leak or ? in one at least you have 50% of brakes left to use, otherwise your whole system is gone!! There are check valves etc to stop back flow from one to other as well. Driving air brake equipped vehicles in Canada requires an "air brake endorsement" which means  2 days school and test then a seperate test by Govt to be able to get licence.
I enjoyed learning all the system and how it operates.
Now my Brother has to go thru it all to be able to use the 240 we just bought!!!
John H
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Front air tank pressure

Reply #3 –
Quote from: John Haygarth –
The whole reason is for safety. One tank supplies front brakes and other the rear ones etc. If there is a big leak or ? in one at least you have 50% of brakes left to use, otherwise your whole system is gone!! There are check valves etc to stop back flow from one to other as well.
John H
The check valves should be checked periodically. I found mine were not functioning due to the white powder desiccant discussed in another thread corroded them. I checked them by starting the engine and filling the tanks. Shut off engine and bleed one tank and see if air holds on the other by looking at the dash gauge. Then I did it again on the other tank. If the other gauge goes down the check valve is not holding.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Front air tank pressure

Reply #4 –
That is a great tip Barry. Thank you.
Dick, '03 U320 40' Tag, 2 slides, Coach #6075
Full Timers
2009 Honda CR-V

Re: Front air tank pressure

Reply #5 –
I will be doing things like that once I get my pit in the ground dug and finished. Been busy with a host of things to house, guests and buying Foretravels!!! Should be able to get it done this fall after our hot summer has gone and trip to NJ over etc
John H

ps  as usual the Barry's and others come up with great tips for us all!
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Front air tank pressure

Reply #6 –
I did as Barry suggested.
Charged air tanks to the max. then bled air pressure off front tank and rear tank held pressure for over one half hour.
I then charged air system again with engine compressor and bled air off rear tank and front tank held pressure for over half hour.
Hope this doesn't come around a bite me down the road.

By the way Brad, my front pressure gauge also lags behind the rear gauge when tanks are charging.
'02 U295 36'
Build #5937

 SKP#104358
Motorcade#17428

Re: Front air tank pressure / precharging the air tanks

Reply #7 –
This might be sort of off in left field but something I have been wondering about ...

When the coach air pressure is up you can tap into the air system at the air hose connection in the LP tank bay to fill tires (coach, bicycle, whatever) or anything else that needs air. 

In my shop I have a 10 gallon air tank that I can fill from my compressor with a male/male hose so that I have a limited portable air supply without taking my compressor.  I use this for my trim and finish nail guns.  I also use CO2 paintball gun air tanks and a regulator for the same thing.

Can I precharge the air tanks on the coach using my compressor and a male/male airhose connected to the air hose connection in the LP tank bay?    The compressor is oilless.  I would probably need an air dryer filter like I would use for spraying finishes.

I usually let the coach idle for a while after starting so this isn't a big deal.  Just wondering if it is possible and if there would be any negative issues that might result.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Front air tank pressure

Reply #8 –
Roger, You got it.  Hook up an outsdie air source thru the hose fitting on the coach using a double male quick connect.  This way you can air up the bags without starting the engine.  You can also use the onboard air from the same fitting to air up tires etc. Be sure you open the valve at the air hose to begin with. Also If you have to be towed the air bags MUST be inflated, the tow truck operator can air up the system the same way.
If you do not have enough pressure to air up a tire you can increase the air pressure in your on board system by adjusting the Governor.
Gary B

Re: Front air tank pressure

Reply #9 –
Quote from: Tom Endres –
....

By the way Brad, my front pressure gauge also lags behind the rear gauge when tanks are charging.
Thanks, Tom.

Roger, on my 2002, there is a switch on the side by the driver to let the onboard 12 volt compressor fill up the tanks.  Was helpful to do that when I was playing with the air cylinders on the steps, and I have heard others comment that they like to use that switch to minimize the amount of noise generated/idle time required to fill the tanks.  I am not sure what years they put that handy switch on.
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)

Re: Front air tank pressure

Reply #10 –
Gary,  Thanks.  I'll give it a try.  I'll have to look to see if there is a valve somewhere behind the air connector.  It always seems to have air if the tanks are up to pressure. 

I am going to increase the air pressure a bit.  It runs about 100 to 110 psi.  My front tires run 102 psi and the rears at 96 psi.  So there is not much room to add air.  I had a valve stem that was leaking, fixed that and a TPMS sensor that leaked, fixed that.  Now the only variation I see is from ambient air temp over the seasons. 

Brad, I looked for a switch over by the driver (inside) and didn't see one.  Maybe it was new in '02 or it was added.  I don't think that the 12v compressor does much in mine except provide air to the leveling system when parked.  After a couple days there isn't much air left in the tanks.  They pump up fairly fast especially on fast idle (I discovered there are two fast idle speeds).  I hate to sit there idling when leaving a more crowded campground.

What a great place to get help.

Roger
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Front air tank pressure

Reply #11 –
Quote from: Home2fromHastings –

Brad, I looked for a switch over by the driver (inside) and didn't see one.  Maybe it was new in '02 or it was added.  I don't think that the 12v compressor does much in mine except provide air to the leveling system when parked.
You may be right that they changed in 2002. Sorry.  Maybe it is an easy retrofit?  Here are pictures of my switches:
The selected media item is not currently available.Brad & Christine Slaughter
Was:  1990 U280 36'
Was:  2002 U270 36' (With a bathroom door) Build #5981
Is:  2021 Leisure Travel Van Wonder 24RL
2015 Jeep JKU, 2003 S10 QC 4x4 or 2017 C-Max
Lake Havasu City, AZ (or Gillette, WY)
 

Re: Front air tank pressure

Reply #12 –
Yup, I have three blank switch covers there.  Time for some research.

Roger
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN