Air Leaks 4104

[4104SoFl]

When I fill the air tank that is below the driver seat with the shops air compressor the air gauge will read 120 and the air bags will fill up. The brakes will not release. I have to crank the bus up and build air pressure. When I build air pressure in this manner I can only get about 75 lbs on the gauge. There is a leak some where in the rear axle area. It will leak down to about 35 lbs then hold. The leak in the back stops. Any ideas?

[RJ]

NAME? -*

There are check valves in the system that only allow air to flow one way, so you cannot totally fill all the air tanks from the front.

Try filling the coach's air system from the engine compartment with your shop air and then report back to us what happens.

FWIW & HTH. . .




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[4104SoFl]

RJ do you want my full name. I not hiding from anyone.

[chessie4905]

   General location; at least the state you reside in. I always filled mine from that tank. What kind of parking brakes do you have? DD3's or Maxi's?

[4104SoFl]

OK RJ aired the system from the back by the motor. 120 LBS. As soon as I stop air it up the gauge began to fall. There is an air leak by the rear wheels, but it not much. Is it possible that the air compressor can only produce about 75 lbs of pressure? Is this a sign that the compressor is shot?

[gus]

If your air bags stay up your leak is in the brake system. They use a separate Auxiliary system at the front tank. If the air bags leak down a leveling valve or connection is probably leaking, they do that a lot.

If the leak is at the left rear wheel and the bags stay up you probably have a leak in the wet tank just aft of the wheel or in an air line from the tank. This tank is notorious for rusting out. It is well hidden up high forward of the firewall! The drain valve at the bottom of this tank is also bad to leak.

There is also a check valve just forward of the compressor muffler. If it fails the air will leak down.

First solve the leak problem then check the comp. It is probably good.

4104 is designed for only 102 psi in the system so 120 will only cause more leaks.

4104s don't have spring or Maxi's unless added on.

[chessie4905]

"The brakes won't release."

[4104SoFl]

Brakes will release. Compressor will pump to about 75 Lbs. I can move the bus. Air leaks seems (SEEMS) to be coming from the air brake canister itself. I did pull it and replaced the diaphragms. It had two and has two air lines running too it. I do not know what kind of brakes they are. Mr. Bonagura from US Coach says he sure they are not D3, because they do not have three lines. These have two. I replaced those diaphragms a few month back. I believe that a good strong compressor would pump to 105 even with this small of a leak. I could be wrong. Any thought or comments would be welcome.

[luvrbus]

Could be the compressor is set to kickout at 75 lbs have you tried to set the governor ? also if the compressor has a air filter mounted on it check and be sure it is clean with a bad filter they will not pump up

good luck

[B_K]

You say you replaced the diaphragms. When you did this did you have part numbers for the chambers to get the right diaphragms?
If you had a part # off a chamber it would tell you what chambers you have.

Also a good way to find the leak is to leave the shop air hooked to it while listening and spraying bubble solution on air lines, brake chambers and anywhere else that could be leaking.
  BK 

[luvrbus]

I wonder what he has for brakes? most spring brakes are sealed to keep you out of harms way with the spring

[robertglines1]

If the sealing surface for the diaphragms was rough or dirty=  when new ones were installed the new ones would leak also---rite?   worth a re-check with soap bubbles?   

[B_K]

Clifford & Bob I agree with both of you!

I know for the longest time (until I got brave enough to actually split 1 apart) a DD3 I was scared to death it would be loaded with a spring big enough to flip a bus!

I had years ago seen a spring from a regular "spring break" chamber go through half of a cinder block and drop down inside the wall of a shop.
Never saw the reason to split one open again after that since they are cheap enough to replace instead of someone losing their head trying to say $30-40.
  BK 

[4104SoFl]

Thanks for all the help. I had to move the bus of the concrete pad and bring my 28' trailer up. It needs brakes and some other work. I will haul it to GA with the 1 ton dodge for Thanksgiving. Taking some furniture up there to kin folks. I will be back on the bus in December. Thanks Again

[chessie4905]

   Did you have to use a threaded tool to seat the emergency spring before separating the halves to replace the diaphragms?