Foretravel Owners' Forum

This is showing tank pressure has leaked down to zero?

Yes, the tanks go to zero after a while.  I've never watched it closely, but say, over a day's time at most?

I imagine if I worked at getting rid of all the air leaks, I, too, could ignore whether HWH re-leveling is working or not.  :) But it seems easier to fix the leveler than to hunt leaks (and hunt them again, next year, etc.).

If I understand from others' posts correctly, there are protection valves on the tanks that are supposed to keep them from completely emptying.  If the tanks are leaking down that fast, it's putting more work on the engine compressor to keep them up for braking while driving.  I'd strongly consider finding and fixing whatever leaks are causing the tank issue.

That way if you blow a big line off of an airbag or something, you don't lose stopping power.

there are protection valves on the tanks that are supposed to keep them from completely emptying.  If the tanks are leaking down that fast, it's putting more work on the engine compressor to keep them up for braking while driving.

That's not my understanding of how air brakes work.  If the compressed air storage failed catastrophically, the maximum stopping power would immediately be applied.  Kind of the opposite of "losing", eh?  I would definitely lose the option to go somewhere, though.  LOL.

Do I have that wrong?

I'd like to separate the discussion of air brake tanks from the issue with HWH re-leveling, if we can.  (Maybe we can move this to another thread?)

On these coaches the air holds the brakes open and if you loose all air they will slam shut and lock up.

No you are correct. On these coaches the air holds the brakes open and if you loose all air they will slam shut and lock up.

No you are correct. On these coaches the air holds the brakes open and if you loose all air they will slam shut and lock up. I was just lazy with my previous response. Basically the protection valves just save enough air for the critical functions... like moving to safety in the event of an emergency air loss.

Yep, gotcha.

FWIW, my other two motorhomes (Newell, Newmar) both had both tanks go to zero when camping.  I'm not sure over what timeframe, but at least a day or more I'd guess. 

I've just assumed they all work that way -- in the absence of an aux compressor that's configured to refill one of them, of course.

Like previously posted the gauges should have stopped at 60 psi. D.O.T. requirement for air systems.

Yep .... kind'a
Your maximum stopping power is with your "service brakes", not the spring loaded "park brake".  If your traveling down a steep grade and loose all air.....the park brake should bring you to a stop......eventually. Depends on the length of the grade I suppose.

I went looking for this requirement, and all I could find is that 60psi is the threshold below which a warning light must come on.  And some other requirements about maximum psi loss per unit time, all of which were pretty reasonable (rapid).

It sounds like a nice safety feature, and I don't think my 24-hour leakdown precludes its existence/functionality in this rig, either.  (Testing that seems like it would require me to simulate a major leak downstream somehow.)

For what it's worth, my tanks are at 35 and 10psi respectively after 28 hours.

There are protection valves on the tanks for the brakes that are supposed to close at 60. Since your tanks are dropping below that, you probably have leaks on the protected side of those valves. The schematic below shows the protection valves on two brake tanks and the check valves coming from the wet tank. The brake tanks should close themselves off from the rest of the system if the pressure gets below 60 and maintain some pressure for braking.



You can test the strength of the parking brake by turning on the brake while driving. I suggest doing it while moving slowly in a parking lot. But it's just a gentile brake application, and just the rear axle.

For the leveling, if this schematic matches yours, the 12v compressor should kick on and supply air to the leveling system and be able to level without any air in any of the tanks.

Can the protection valves be removed and cleaned internally, or do they need to be replaced if leaking by?

My coach's air tanks have always gone to  zero after about 1.5 days. I know for a fact my entire air system had the dreaded white dust just about everywhere. I have been slowly removing,cleaning, etc all parts of the air system now for a few years. If the tanks are supposed to hold air indefinitely due to the protection valves, I surely want to take the time to clean or replace. Probably also the treadle valve

The valves are not expensive, not worth the labor to repair.

1. Is the brake treadle valve rebuild-able,
2. or one of those best to just replace?
3. If replace, anyone got the part number?
4.Guessing not a 1 size fits all.

1. Yes
2. depends on your skill and $ availability
3. refer to #4
4. Correct. This is one thing that you get the part number off the valve and get the rebuild kit for that valve.

Mike

There should be a metal tag on the treadle valve. Take that number to a truck brake parts dealer and they can give you the correct one. I always just replaced the complete valve. They come as rebuilt.