[Brad Townsend]

Thanks cj. Lots of wind here. Won't be moving till sometime first of April. Hopefully we will have some nice weather between now and then

[77newell]

Quoting Richard's Post "In my way of seeing it, if both the brake system and the supply system are leaking down then the massive leak has to be upstream. So Clints suggestion of looking at the air drier blowoff, check valve, and system between the engine air compressor and the first wet tank is logical".

I can't believe I'm going to disagree with Richard, but here goes. YIKES. Given that the air can only flow in one direction from the service tank to each of the brake tanks due to check valves in the lines connecting them, then if there is a leak anywhere upstream of those check valves the pressures in the two brake tanks would remain uneffected. Yes the service tank would deplete, but not the brake tanks. It is true that if there is a leak in the early part of the system (compressor, drier, service tank) AND both check valves are failing to act as check valves then all three tanks would deplete as you have described, that combination of failures just seems unlikely to me.

Yes Brad I was referring to the drain valves on the bottom of the brake tanks, especially if they are the auto drain type like I had failures with.

[Richard]

Jon,

Absolutely no offense taken. This will be interesting as Brad tracks the leak down.

[Richard]

This is where I am confuseded (as my three yr old once said). I always thought the air from the engine compressor via the desiccant drier goes first to the wet tank before it goes to the brake tanks. I assumed that somewhere in the desiccant drier or upstream of the wet tank is a check valve. There has to be a check valve because the engine compressor unloads and exhausts at the drier.

[MrE]

Wouldn't this be a fun seminar at Ruidoso?

[77newell]

There is a check valve at the outlet of the drier, so yup, Richard, you got that right. As far as I know there is no other check valve(s) until after the "service" or "wet" tank (two names, one tank). Each of the brake tanks has a check valve on the inlet supply from the "service" tank so they are isolated from each other. That way a single leak associated with one of them doesn't effect the other, but that leak will tend to also deplete the "service" tank. As long as the supply exceeds the leakage rate the pressure will be adequately  maintained and the emergency brakes won't deploy. Your compressor may cycle a lot but you won't be stopped. This appears to be Brad's situation.

Richard: the only time I'm not confuseded is when I'm wrongerer.

[RussWhite]

Like I said in the first post to this thread. There is more than one thing wrong here. Yes, one of them could even be the exact description of the problem by the OP, but you can't lose air in both brake systems with a single point of failure.

[Brad Townsend]

I am assuming the air dryer is the unit that looks to be around 4 inches diameter about 12 inches long, is finned its entire length and is where the air blows out when it reaches top pressure. There are 2 wires at the bottom. If this is the check valve mentioned by Jon then it would be pretty easy to CHECK out.

[Richard]

yep on the air dryer


Thanks Jon for the info on inlet check valves to the brake tanks.

Russ may be on to something. Brad will you look your original post over and confirm that the info mirrors what is happening? Do you have any more info about the behavior of the system? All of us armchair mechanics are trying to help via remote control and we are no better than the info we have to work from. No offense intended to you, but as you have read the posts and studied the issue more, perhaps something comes to mind.

[77newell]

Brad: if air from both brake tames is leaking out through the vent on the dryer, that would require three failed parts; the check valves in the dryer and in each of the two brake tanks. It is possible though unlikely.