Releasing Air From Rear Bags

[Guest tmoning]

I have a 2004 Fleetwood Expedition diesel pusher. The suspension's dump valve releases air in the front air bags quickly, but it takes the rear bags a few minutes to go down. Sometimes I raise the rear with the levelers a little, then let them down and bleed the air out. What would you suggest I do to make it right?

[Guest tmoning]

Since the front air bags dump fine but the rear air bags take longer, the most likely cause is that there's a restriction between the rear suspension and the dump valve. Check the plastic air line leading from the rear suspension to the dump valve to see whether it is pinched somewhere. Another possibility is water in the air bag suspension.

The following is merely for your information, as I do not know the specifications of your 2004 Expedition. I suggest you check your coach or have it checked to see whether it may have a system at least similar in function to the one described below, but not necessarily in the same locations.

Our 1995 Winnebago Vectra is factory-equipped with a unit identified as a “Midland Grau, Pure Air Plus†system, which is frame-mounted directly behind the right-side dual wheels. It is a two-piece metal air cylinder with a clamping band at the center. This unit is approximately 12 inches in diameter and 8 inches high. On top of this air cylinder is a spin-off/spin-on desiccant-filled canister that measures approximately 5 inches high and 6 inches in diameter. This is said to be a coalescing filter. This unit’s 5/8-inch air line plumbing is connected between the engine-mounted air compressor and the frame-mounted reserve air tank, which is the onboard air supply for anything and everything that uses clean and dry air pressure.

[lanerd]

To release my air quicker than the air release valve will allow, I simply push and release the brake pedal three or four times. This will deplete the air remaining in the air tanks quite rapidly.

Ron

[tmoning]

To release my air quicker than the air release valve will allow, I simply push and release the brake pedal three or four times. This will deplete the air remaining in the air tanks quite rapidly.

Ron

If this advice is followed with the parking brake on, and the service brake is applied hard, you are "compounding" the rear brakes (and can do major damage!).

[mancina]

Is there a way to manually override the rocker switch for the air dump? I noticed this weekend that our rear would not dump, but the front suspension did release and lower? We have an 09 Crescendo Gulf Stream with a Workhorse Chassis.

[hermanmullins]

Guest,

Your system has two solenoid valves for dumping your air bags. I had the same problem and found they were stopped up with dirt dobbers nest. Cleaned them out and wala, down she went. After that I put small filter on the valves to keep it from happining again.

Hope this helps.

[chucknewman]

Along the same line as Herman's post, which is not unusual if the coach is sitting for a long period, is that I found a mud dobber nest on my PacBrake air solenoid exhaust port during a pre-trip inspection after sitting for six months.

In your case the air exhaust rate appears to be changing, I would suspect a sticky air solenoid. Usually gets worse with colder temperatures.

Tmoning posted "If this advice is followed with the parking brake on, and the service brake is applied hard, you are "compounding" the rear brakes (and can do major damage!)."

Compounding is the combination of two forces: the force applied by the spring brakes and the service brake. The anti-compounding valve features in the

system design help prevent the application of both the spring and service brakes together. Our MCI bus has a R-14 relay valve (anticompounding valve) to prevent this issue. Some manufacturers use an R-7 modulating valve for this protection.

Assuming a federally compliant air brake system, how and where does "major damage" occur?

[wolfe10]

Chuck,

You are correct. IF the air system has an anti-coumpounding valve there would be no damage. But, with the wide range of chassis over the years, it might be wise to verify, not assume.

Heck, I have worked on coaches with air suspension and air brakes that had no dryer. Draining the wet tank produced several GALLONS of rusty water.

Brett

[hermanmullins]

Brett, did you say you got rusty water from your bladder or tank?

[wolfe10]

Herman,

Wait a minute-- isn't that getting a little personal?!

OK, seriously, no, definitely NOT on our coach. We have an air dryer and I keep it serviced.

This was on a Beaver Monterey that came from the factory with NO AIR DRYER. Just a note that said "Drain tanks daily". I met the owner in an RV park in central Mexico where we were staying-- he was having all kinds of air suspension issues. Opened the drain on his wet tank and shot a stream of rusty water all the way into the next campsite. And, it just kept coming .....and coming..... and coming.