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Help diagnosing air issue

1998 U-320 36' M11 Celect Plus
Leveling system:  HWH 600 series.

I could use some helping figuring out how to troubleshoot a potential air issue.

After getting new tires on Monday, and re-parking the coach on the drive, I noticed that after about 1-1.5 hours the front driver side air bags had deflated so the coach was resting on the wheel.  The front passenger side air bags, and L&R rear airbags had enough air in them to keep the chassis off the wheels.

Air bags are two years old.

The front and rear dash air gauges read the same PSI and were around 100 PSI.

When I turned the ignition to "Accessory On" (engine remains off) the left front air bags filled back up and raised that corner.  At this time the front dash air gauge dropped PSI while the rear dash gauge stayed steady.

As I reason through this it appears to me that there is a leak between the two front left airbags and the ports on front six-pack.  My understanding is that each airbag at the corner goes to it's own port on the six pack, but air flow into both those bags is controlled by a single travel solenoid for that side. 

I think the left travel solenoid is still good and holding.  If it were bad I would expect the front air gauge would drop due to air leaking, and I would not expect the left front corner to raise when the key was moved to the "Accessory On" position.

Does my reasoning sound right?

I have moved the coach to a more level spot, measured fender heights, and will let it sit for a while and remeasure.

Is there something else I should do or check to trouble shoot this?

Thank you,
Chris

Re: Help diagnosing air issue

Reply #1 –
 Chris  I sent you a PM.
John Duld
1995 U320C SE 40'

Re: Help diagnosing air issue

Reply #2 –
If you have your HWH manual check it out,has troubleshooting.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Help diagnosing air issue

Reply #3 –
Thank you both for your replies.

Chris

Re: Help diagnosing air issue

Reply #4 –
 Chris,
Be sure you are on level ground when you are comparing the travel height, one side to the other.
John Duld
1995 U320C SE 40'

Re: Help diagnosing air issue

Reply #5 –
Ride height levers look fine.  HWH manual troubleshooting steps don't cover the situation I'm seeing. 

The driver side air bag leak down takes place with the key removed from the ignition and the leveling system off.

Front and rear dash air gauges read the same PSI with the engine off and leveling system off.

Within an hour both the driver side air bags (both of them) leak down so the coach rests on the tire, but the loss of air in those front bags does not affect the front dash air gauge.

I've used the HWH control panel to raise the ride height while stationary, and all bags inflate.  I've cycled the raise and dump valves a number of times to clean out or unstick valves.  The coach goes up and down.  All the solenoids and valves seem to work as they should.

When the engine turns off the driver side air bags go down quickly while the remaining six bags hold air as they should.

I'll check for loose hose fittings for those bags on the manifold, or cracked lines.

Chris

Re: Help diagnosing air issue

Reply #6 –
If the air bags are loosing air quickly, you should be able to hear the air escaping. Probably one of the solenoid valves on the six pack for that set of air bags. Check at the exhaust port on the six pack and also the ride height valve. Also check if maybe an air line got damaged when the tires were changed.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Help diagnosing air issue

Reply #7 –
Red - Thank you for the reply.

I had a nice talk with James at Foretravel today about the leak down.

The most likely culprit is the Dump/Lower solenoid on the front six pack.

James shared that the easiest way to check the dump solenoid for leaks is to cover almost all of the dump solenoid's exhaust port on the six pack with tape, and then use soap bubbles on the remainder of the opening.

He recommends covering most of the hole with tape because it is much easier for the soap to span a smaller hole than the larger exhaust port hole.

Why is this the most likely culprit?

The indicators are:
    • the rapid leak down happens when the engine is off
    • the rapid leak down is isolated to both airbags for one tire only
    • the leak down does not affect the dash air gauge reading

If it where a ride height lever problem, then the airbags for both front tires would be leaking down - this is not happening.  The coach's front ride height is controlled by a single ride height lever/valve that adjusts both driver and passenger side.

If it was a leak at the air tank then it would affect both tires, and the dash PSI gauge would be affected - this is not happening.

With the engine off none of the solenoids are energized/activated.  It can't be the raise or travel solenoids being stuck because air is not moving from the front tank to the bags - the PSI gauge doesn't drop and the bags don't inflate

Once the ignition switch is moved to the "Accessory ON" position the solenoids are energized/activated.  Now the bags begin to inflate and the dash gauge shows dropping PSI.  This tells us the travel solenoids have opened and air is moving from the tank to the bags.

A new solenoid is on order.

Chris

Re: Help diagnosing air issue

Reply #8 –
I wanted to update this and wrap it up a bit.

The problem appears to have been one of the front 10 PSI air pressure switches leaking and not the dump solenoid.

A new brass fitting and pressure switch were installed.  No audible leaks.  Joints passed the soap bubble test.  Dump solenoid vent hole isn't showing signs of air leaks.

Coach has been sitting for the amount of time that it used to take for the air bags to deflate, but now the air bags are still full.

So, the 10 PSI pressure switch can also cause a leak that will bring down both airbags at one wheel.

Chris

Re: Help diagnosing air issue

Reply #9 –
Quote from: Numbers –
So, the 10 PSI pressure switch can also cause a leak that will bring down both airbags at one wheel.
This is a extremely valuable piece of information that will hopefully be remembered by some member if this particular problem ever comes up again.  I, for one, would never have thought of the pressure switch as being a potential source of a leak!

Glad you got your problem solved, and thanks for posting the final solution.  ^.^d
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Help diagnosing air issue

Reply #10 –
Where is that pressure switch located?
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT

Re: Help diagnosing air issue

Reply #11 –
Quote from: GleamB –
Where is that pressure switch located?
Front 6-pack manifold.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"