On a 2005 T-800 Kenworth with a 475 Cat the air system when completely drained, will only fill one tank at a time. The second tank won't fill until the needle is at 105 psi.
Anyone know why and how to fix this problem.
Thanks

 

check for contamination (oil/water) in your tanks, sounds like the "second tank" check valve is sticking

 

I would bet that this truck has a Bendix AD-IS or DRM air dryer installed. If it is, it is normal operation.

For the AD-IS see page 4 where it says 106 psi: click here (be advised these pressures can be variable)

For the DRM see pages 3 and 4: click here (as I recall the DRM was developed specifically with kenworth in mind.)

Let me know if this fits with what you have.

Birken

 

Thank you for taking time to help me solve this problem. I have been out of air every day but didn't realize this system was supposed to work this way.
So I guess I have to just find the air leak so the system isn't drained.

 

One place I'd check is the air line going to the fan clutch with a spray bottle of soap or windex for leaks.
On my 01 KW w/c15 this line had pin holes all over it that I noticed leaking when washing the engine.
It's a cloth covered rubber line. A plastic line replacement would be a better option even though I just replaced mine with the same original type.
Now the truck will hold air for days.

 

Well if both reservoirs are empty in the morning then you have more than one air leak.

Basically how it works is if system pressure drops below 105 psi then the pressure protection valves close, isolating the reservoirs from one another. (When pressure is up the reservoirs are all connected together, wide open, with no check valves, very different from the old system.)

So if you go out and check on it every few hours, watch how the air pressure is dropping. Once the needles get below 105 psi (it can be lower though) then they shoud start to fall differently from each other. The one that falls faster is the one that has the major leak.

But, basically you just have to go after it with the old squirt bottle if you want it fixed, or just live with it.

Birken