Sorry, another air leak post. In about 8 hours both gauges simultaneously go to zero. The check valves appear to work properly as they don't change pressure when wet tank is drained. I have sprayed everything with no obvious leaks. Anyone have any ideas. Thanks
Have you checked the stairwell cover air ram? and how about the air regulators.
Yes
If the protection valves are working correctly they would only let the air pressure get down to around 65 psi on the front and rear air tanks, so leak(s) are somewhere else. I am assuming that when he says both air gauges he is talking about the gauge for the front and rear tanks.
Did you check the drain valves and the fittings?
Yep, I guess I was thinking maybe something that would cause both tanks to loose air. The gauges move the same amount to zero.
If the check valves are sealing properly, the leak must not be upstream of those valves.
As turbojack states, if the leak was downstream from the protection valves, then your pressure gauges would stop going down (or at least pause for some time) around the 65 psi level. Since they are not doing that, it would seem the leak is upstream from the protection valves.
This narrows the possible source of air loss down to a fairly restricted space - somewhere between the check valves and the protection valves. Look at your air system diagram and see which air lines tie into the tanks between those valves. Where do those air lines go? Could the tanks themselves be leaking? Having rust holes appear in both tanks simultaneously would be...unusual. The condensate drain valves? You said you checked them.
Good luck.
Thanks, no luck yet. Fun Fun. NOT
Seems to me something in the braking system or if throttle is air operated. Since you have eliminated air leaks at fittings, then possibly a brake module. Have you checked brake pedal or throttle controller in the coach.
Do you have the drawings of air system? Maybe if you posted someone may come up with an idea.
Did you check parking brake valve and fittings?
You have a couple of air pressure switches that are in the piping that is fed off the line going to the brake treadle valve and park brake. These switches are known to leak at the crimp ring.
Mike
Thanks everyone, taking a break. When I get under coach again I will take some pics. I did check parking break switch no leak detected. I didn't check other areas concerning brakes, I did check treadle valve.
Sounds like a big enough leak that you might be able to hear.
Get the air up, turn your hearing aids all the way up 😊 and go around inside and out and listen.
You might get lucky.
Hope you do.
Could gauges be part of the problem
Speaking of air leaks, where do people buy DOT certified brake line fittings? I'm getting Sticker Shock looking at what's offered online!
Fleetpride. Go online and open an account. They will give a discount over regular web prices
You may have a few check valves. Dryer exit for one and one at each tank inlet. If both tanks lose the same values. I would look near the dryer check valve for starters. Simple way to test. Let the air fall to 2-40# and unscrew the cartridge a little. There should not be pressure in the dryer after it purges. Be careful of course.
Trace the lines and see what shares pressure ?
My parking brake leaks pretty quickly in about 5 hrs to zero ish .
My brake treadle valve leaks a little while running , and while parked .
A big bubble, the front protection valve. It is leaking out the little hole. Not sure it is enough to amount to anything.
If you haven't already, try pumping the brake pedal with coach running.
With the air coming out that little hole indicates that the diaphragm has/is failing. Said another way the diaphragm has a hole in it which mean the protection valve need replacing so it will function properly.
Mike
Would this be a proper replacement?
Dan, why are you suggesting pumping brakes? Thanks
Does it cross-reference?
Part Number Collection (https://www.foreforums.com/index.php?topic=11472.msg493926#msg493926)
Reservoir Pressure Protection Valve - 1/4" NPT, 65 PSI
Haldex: 90555396
Midland: N15759DG
Meritor Wabco: 9348990060
Am I to assume the right tank uses same valve? Looking at that tank, it has been replaced with this valve.
Yes
Those valves should be rated to close at about 60-65 lbs. the one listed in reply 19 it closes at 45 which leaves you little pressure to get off the road before the spring brake will set.
Mike
Happened to me one time on a Bluebird coach when I was still a novice RVer.
Had camp hosted for 5 months. When ready to depart could not build air pressure. Checked around, heard leak by treadle under front of coach. Hit the brakes a couple of times and it resolved itself. Never happened againn.
Thanks, I will try it.
Maybe the pressure release valve stuck a bit.
As you let off of the pedal.
Sorry I am getting confused on which protection valve to buy. These other cross reference valves say open at 70psi close at 65psi. This PAI valve says open 65 close 45. Would I be better off with the close at 65psi or match left tank with right tank? Thanks
Close at 65. You want more air in your tanks to stop. If your existing one close at 45 psi you need to change that one also
I had a feeling I was going to get that response. That one doesn't appear to be leaking, double the fun I guess. Thanks
Better knowing now and getting it fixed, instead of being out in the middle somewhere in the middle of the highway with the parking brake on.
For sure
My throttle valve is a substantial leak right now and I hope the parts are OTW.