Air Brake Concern

[itdave]

Hi Folks,
I need some help or suggestions on an issue I am having with my air brakes. Earlier this week I pulled the MH out of storage and noticed that the rear passenger corner was lower that the other four corners. It had been there for a few months so I just figured that the passenger rear air bag had a slow leak. Started the MH the air came up to pressure and the coach came to ride height on all four wheels. After driving for 15 or 20 minutes I notice that the red needle in the pressure was falling quickly (less than 5 minutes) from 135 to 90. The green needle was falling but much slower. This was happening while driving on a freeway at about 60 MPH with little or no use of the brakes. Of course when the red needle hit 90 the compressor kicked in and brought the pressure back to 130 to 140 psi. This kept up for most of a 4 hour drive, sometimes the needles would stay together. After stopping for gas we started out again and when I hit the brakes lightly one of the rear wheel locked up for a couple of seconds. I stop and check things but could not find anything wrong so got back on the road no more lockups but the tank pressure gauges kept falling and then going back to 140.
Today I called Monaco and they said to take it to a service facility. I took it to Cummings West in Bakersfield. They could not locate any external air leaks and could not see the problem when they tried a short test drive. The brakes passed the DOT test for air brakes. They think there may be a internal problem with the rear air brake chambers but had no idea how to test them.
I am hoping that one of may have had this problem in the past or have knowledge about air brakes so you can get me pointed in the right direction. Thanks for the help.

[bluepill]

Quote:

Originally Posted by itdave Hi Folks, I need some help or suggestions on an issue I am having with my air brakes. Earlier this week I pulled the MH out of storage ......

Brakes are especially temperamental when not used for awhile. Linkage, valves, etc. can get sticky. Drums and rotors can develop rust on the friction surface.

Before you go further in diagnosis, I would suggest a run or two for at least 1/2 hour. Use the brakes harder and more often than usual (traffic permitting) to excercise everything. That may be all that is needed,

[itdave]

Just for the record I drove from Sedona AZ to Bakersfield about 600 miles with this problem. Only one lock up but gauges are still acting funny.

[nodine]

Quote:

Originally Posted by itdave Just for the record I drove from Sedona AZ to Bakersfield about 600 miles with this problem. Only one lock up but gauges are still acting funny.

Dave,

Just guessing but it sounds like a valve is sticking.

Good luck,

Bob

[Jimmy F]

itdave,

Have you tried listing for an air leak with the park brake off?

You may have a leak in one of the diaphragms in the spring brakes. You won't hear a leak if you are parked with the brakes on. The air will only leak when the brakes are off which applies air to the brake chamber rubber diaphragm which releases the park brakes.

Air up your coach, block the wheels so it won't roll, shut off the engine and release the brakes. Get out and have a listen.


Jimmy

[slickest1]

It could be the air dryer ( if so equipped) is bypassing. When your compressor builds the air up the air dryer lets off a burst of air when the tanks are up to pressure. Just build up the air until your air dryer blows off and the shut off the engine and check to see if there is any air leaking out the bottom. Also could be the air governor. Try this after checking out the other things mentioned above. I would think a cummins shop would have found the problem unless it corrected itself. Sometime things just get sticky from sitting.

[itdave]

Jimmy thanks for the advise tried what you suggested but could not hear a leak. The problem only seems to happen after I have been driving for 10 to 15 minutes so it is hard to replicate when parked. Looks like I will keep searching.