After engine shutdown with full air pressure in the suspension our coach has started emitting a loud hissing noise and quickly the back end begins to sag. It didn't do this until after we got it back from the shop that did our safety and emissions tests.
The front stays up although after several hours both ends of the coach have lost air and are level again.
I've been crawling around under there and found the hissing noise comes from the rear height control valve. Air is rapidly being lost thru what the Neway AirRide section of the Spartan service manual calls the "Top Port Exhaust". There is an identical height control valve on the front that doesn't lose air thru the exhaust port.
Also, the control arm to the flexible link on the leaky rear unit can be pivoted up and down. If I manually move it down air rushes out of the exhaust port. If I push it up the hissing decreases a lot or even completely for a bit. On the front height control valve the control arm can't be moved up or down manually and you can't hear air escaping either.
There's a thing called a "adjusting locknut" on the control arm. Maybe it has just come loose and so allows the control arm to move and exhaust air from the system? I'm thinking I might get back under there in the morning and put a wrench on the locknut to see if it can be tightened. Or maybe the valve is just kaput?
Also, upon startup, one air pressure gauge moves up to pressure faster than the other, but both show full pressure and there appears to be no problems with air pressure when on the road.
I dont really know a thing about this stuff except what I've learned by reading the Spartan Bible since I crawled out from under.
Any thoughts or assistance is gratefully accepted.
Don ... 1990 Regency

You should not be able to move the height control valve without loosening the set screw. If it is loose I am surprised it stays up with the engine running.
As overview, on buses at least, you have one height valve in the front and two in the rear. The two in the keep the coach level side to side and the one in front is to keep it level front to rear. Many MHs use the air bags to level. This means you have to bypass the height control valves when parked. Our Newell has the HWH system which sitches to height control valves as soon as you turn on the key.
Just a quick summary. Good luck.

Duplicate what you see in the front - A 90 degree angle is level.

If the arm is DOWN you will loose air because the height control valve thinks it's too high - air will vent thru the exhaust port

If the arm is UP it will add air because it thinks the coach's level is too low - overfill the airbags

I'm trying to figure out what, if any, problem we have with the air suspension on our Regency.
The rear height control valve lets down the back end faster than the front does.
The coach is perfectly level when running. The height control arms are horizontal on the front and rear but the rear one leaks air from the exhaust port when you turn off the ignition.
I take it it should not. The coach has hydralic levelers when parked, not air levelers. It has only one height contol valve on the street side front and only one, also street side, at the rear.
After sitting parked overnite both guages register zero air pressure, you can see the coach has lowered itself on the suspension but has done so equally and is perfectly level.
Is this normal? Or should the system hold pressure indefinitely? If you have a similar setup, how does yours behave?
It only sags in the rear for the time when the rear has lost pressure fast and the front hasn't caught up to it yet.
It has had no effect on the operation of the coach in any way.
After start up you can see that the left guage takes longer to start building pressure than the right one. But, by 50 - 60 lbs they even out and reach 120 -125 lbs at the same time and maintain that pressure as long as the motor is running.
Can somebody give a brief explanation of how the air suspension is supposed to work? I'm trying to figure out if i need to take her back in for service but don't know enough about how she works to know what to do.
Thanks
Don ... 1990 Regency 34' Cummins 8.3CTA/Spartan

quote:

Originally posted by Don in Niagara:
I'm trying to figure out what, if any, problem we have with the air suspension on our Regency.

Good place to start - Ask and see what happens.

quote:

Originally posted by Don in Niagara:
The rear height control valve lets down the back end faster than the front does.

This can be caused by a bad bag, airline or valve

quote:

Originally posted by Don in Niagara:
The coach is perfectly level when running. The height control arms are horizontal on the front and rear but the rear one leaks air from the exhaust port when you turn off the ignition.

Turn on the ignition but do not start it, does it stop leaking?

quote:

Originally posted by Don in Niagara:
I take it it should not.

No, it should not leak.

quote:

Originally posted by Don in Niagara:
After sitting parked overnite both guages register zero air pressure, you can see the coach has lowered itself on the suspension but has done so equally and is perfectly level.
Is this normal?

Doesn't sound right.

quote:

Originally posted by Don in Niagara:
Or should the system hold pressure indefinitely?

This is subjective. Getting a 100% seal on a 17+ yr old coach on an air suspension is almost impossible. Most Fire trucks have an airline attached to it so it always has full air. You're not driving a Fire truck so it's subjective to your expectations and wallet ouch factor.

quote:

Originally posted by Don in Niagara:
It only sags in the rear for the time when the rear has lost pressure fast and the front hasn't caught up to it yet.

Normal for the way you're describing it.

quote:

Originally posted by Don in Niagara:
It has had no effect on the operation of the coach in any way.

For now...

quote:

Originally posted by Don in Niagara:
After start up you can see that the left guage takes longer to start building pressure than the right one. But, by 50 - 60 lbs they even out and reach 120 -125 lbs at the same time and maintain that pressure as long as the motor is running.

This is normal - the primary and secondary have a check valve between both systems - at 50-60 lbs the check valve allow the psi to build together.

quote:

Originally posted by Don in Niagara:
Can somebody give a brief explanation of how the air suspension is supposed to work?

There is supposed to be a low psi cutoff between the airline supply and the height control valve. At 60lbs the coach should hold the psi at each of the supplies for the airbags. You should replace the height control valve based upon the symptoms you're describing. Chances are good that you will still loose all of your air - just not as fast.

quote:

Originally posted by Don in Niagara:
I'm trying to figure out if i need to take her back in for service but don't know enough about how she works to know what to do.

If you're passing thru the Newburgh, NY area I'll be happy to look at it for free and to give you some pointers. I-87 exit 17, Just 90 miles south of Albany NY.

Thank you DillNY and everyone for all the help. The height control valve is toast I think. Been crawling around underneath again and a comparison to the front valve shows a lot of slop in the control arm where it mounts to the valve. The result is that the unit will go right past the 90 degree angle with the arm and continue to exhaust air from the system even tho the locknut is secure.
I will be looking to remove and replace at the first opportunity.
Thanks for volunteering your services NY Bill. Unfortunitely we arn't likely to be back your way this summer. The coach came from Putnam Valley, which is very near you I believe.
Don