Front Tank Air Pressure

[Suncruiser05]

I have a 2006 Newmar Kountry Star model 3910.
Front tank continues to run at about 75lbs. When I depress the brake and hold it at a light the pressure will drop below 65lbs. I have to then let the pressure rise to move on. I arrived home had the wife depress the brakes and I hear a large a blast coming out the driver side front. Just wondering what it could be before climbing under to explore.
Thanks in advance, John M.

[Skip426]

Do not go under without supporting the coach with jack stands to the frame !!!

Your description sounds like your air suspension system is leaking .
The 75 psi , sounds like the Brake Protection Valve is functioning , the BPV, is in the system to prevent air pressure loss in the suspension from effecting air brake operation .
Contact your coach chassis builder with your serial number and get an air system diagram .


Spartan 1-800-543-4277

And proceed with caution .

[DiplomatDon]

Check brake diaphragm if only leaking when brake depressed. Good luck, Don

[Ray,IN]

Originally Posted by DiplomatDon

Check brake diaphragm if only leaking when brake depressed. Good luck, Don

I too suspect a failed brake canister.

[twinboat]

Could also be the brake hose to the air chamber.

[Boomper]

Agree with posts 3,4,5.
Absolutely nothing to do with suspension if the air leak occurs when stepping on the treadle valve.

First guess, airline leading from frame to diaphragm had a hole rubbed in it by the tire.

Second guess, blown brake diaphragm (pancake)

[Skip426]

Ok guys , then please explain to me how an air leak at a brake chamber or supply hose , keeps the tank pressure from building past 75 PSI when the brakes are not in use .

Granted there could well be more than one problem; but with his DW applying ( and releasing? ) the brakes , the blast he's hearing could be a " quick release valve " and John's just not used to being outside and hearing it.

Time to start asking questions .

John ; once the engine is shut off , does the air suspension settle down quickly , from ride height ?
Can you run the engine without applying the brakes and have the air tank get to over 75 psi ?
When the front tank is at 75 , what is the pressure in the other tank ?

[Ray,IN]

Low tank pressure might be due to the air desiccant filter being clogged. How long since that compressed air filter was replaced?

[Suncruiser05]

The suspension does not settle down with engine off. With engine running the front tank is barely holding at about 75 lbs and will not go higher even with engine at high idle. I can see the pressure gage go up and down on the front tank. Air blast when depressing the brake is coming out the driver's side. Rear tank is at normal pressure at 120 lbs and holding well. If I depress the brake the pressure starts to drop on the front tank and the warning alarm sounds. We have a mobile mechanic coming out to check it today. We will keep everyone informed on the issue. It sounds like a bad brake diaphragm.
Thanks, John M

[Ray,IN]

The air brakes operate out of the front tank, there can be a stuck/restricted check valve at the input side preventing full pressure.

[Skip426]

Originally Posted by Suncruiser05

The suspension does not settle down with engine off. With engine running the front tank is barely holding at about 75 lbs and will not go higher even with engine at high idle. I can see the pressure gage go up and down on the front tank. Air blast when depressing the brake is coming out the driver's side. Rear tank is at normal pressure at 120 lbs and holding well. If I depress the brake the pressure starts to drop on the front tank and the warning alarm sounds. We have a mobile mechanic coming out to check it today. We will keep everyone informed on the issue. It sounds like a bad brake diaphragm.
Thanks, John M

John ; thanks for answering my questions , but because the tank pressure won't build when the brakes are not in use , I'm thinking you have a couple of issues .
Is the mobile mechanic versed in air brake systems ?
Were you able to get an air system diagram , linked to your serial number to have on hand for him ?

[Suncruiser05]

We were able to get it fixed. All is working well. Left front brake pancake had a broken brass where the air line was connected. Attached is a picture of the problem. Had to go to a truck shop to obtain the fitting. Was able to easily change it through the wheel well and turning the wheel all the way to the left. We need to get a hold of either Spartan or Newmar to obtain a air and electrical diagram for my chassis so I can have it handy.
Everyone thanks for all the help, John M.

[Skip426]

John; thanks for wrapping up your post , glad it was an easy fix ; although I still can't figure why the air pressure wouldn't build when the brakes were not in use.
Spartan is the place for chassis info ; wiring and air system ; Newmar would probably just direct you there.

Safe travels .

[Ray,IN]

Did my Spartan compressed air system diagram not appear? Perhaps only I can see the pdf.