Think i'ld make sure the guages were accurate & worked properly. do they build up together? Another thing to check might be the lines going to the guages.....is one kinked somewhere? Then look at lines & valving from the tanks to the foot valve etc. I just don't see a tpv changing anything. Has it always been like this?

 

the gauges are correct. they build up at same rate. well... the one that is the lowest.. # 1 will start to build back up & when it reaches same psi as tank 2 then they both move at same rate. it has not always been like this. I cannot find any leakes anywhere. if i apply pressure to brake pedal & hold, the gauges drop just a couple lbs & hold. as if there is no leak in brake chambers, e.t.c.

I may have found where the tpv is.. the air lines from the gladhands go thru drivers side side box & under floorboard under drivers seat. there then is a valve mounted to the underside of floorboard with a lot of air lines coming from it going to foot valve & other places. there are no leaks or kinks under dash or near gauges or air lines there. i replaced all air valves on truck... leveling valve, front valve wich has a pop off on it,mounted near front bumper on frame, the one on the front rear and going to brake chambers,, & the big one going to all four brak chambers on tractor. had replaced 2 brake chambers a while back that had very slight leak. ( had to wait a couple hours to see leak.) still made no noticeable difference. my biggest concern is #1 tank going too low while having to brake often. whe driving especially downhill & braking due to some rough roads my foot will slightly bouce on the brake pedal & thee # 1 tank will drop like crazy. I gues just one of those things that will dumbfound me until fixed. thanks for all the feedback..

 

hxxp://www.tonystruckparts.com.au/tp3.jpg replace xx with tt and take a look your t.p.v. should look like this

 

How does a brake chamber take a couple hours to leak? They don't get air pressure unless you apply service brake. You held your foot on the brake that long?

Have you shut off truck in quiet place (not a noisy truck stop) wheels chocked, parking brake off and have someone depress and hold brake and you walk around truck and listen for leaks? Quick release valves?

Are you sure you air compressor is adequate? Kinks in line? Air dryer in working order?

 

placed concrete block on brake pedal & went on to other things, then checked for leaks later. the leak & the bubbles were so small, it almost was not worth changing.
I had the old compressor taken off cause it took forever to build air. I let the shop take it off & I took it to truckpro, got an exchange & brought to shop to have them put on. the new compressor did not build air any better than the old one..... that was a year ago. new air dryer 4 months ago. after the down time. i was frustrated & wanted my truck & get back to work & just deal with the slow build of air, but this new problem of one tank going down too quick & almost by itself has added to the exisisting problem. at 120 lbs. & truck off by 8 hours both tanks are on 0 psi. i have put expensive leak detector on everything visible. no leaks. this stuff cost 10.00 a quart. when bubbles are produced from a leak the bubbles remain for 10-15 hours & if their is any condensation or moisture rain e.t.c it will be visible for 24 hours. I wish i could submerge entire truck in leak detector.. lol

 

I finally found tpv.. it was under floorboard just in front of drivers seat. had to take off rubber mat & aluminum floor pans & 50 screws to get to it. 2 dozen air lines uner there. a hell of a place to put it. will be checking for leaks in all the connectors & lines as well as the tpv itself the next day or 2

 

A service side leak that causes one air reservoir to empty twice as fast as the other WILL NOT require leak detector and bubble inspection to find that air loss -- it should be very obvious.

Does the 'excessive' air drop occur before or after you release the service brake application?? If the drop occurs BEFORE you take your foot off the pedal, it would seem more like a problem of air res capacity, or excessive pushrod stroke... this type of thing. If the drop occurs only AFTER you've removed your foot, then the air loss would more likely be escaping through a sticking air valve exhaust port, or something of that sort.

...I wouldn't recommend taking technical advise from a DOT officer.

 

yes Bob . i thought this leak would be easy to find too. i can hold the brake pedal down & it's o.k., when i pump brakes is when #1 tanks drops significantly faster. sooo, holding, no drop ,releasing no drop, its when i pump a 2nd time that it goes down, then the 3rd pump, e.t.c. & after a few pumps the # 1 tank is far below the # 2 tank. i replaced all air valve ports. i do know that there is air that comes out from a huge valve that seems connected to the brake pedal with a lot of air lines to it. thought air only escapes when taken foot off brake & air comes from under a thin wafer like rubber washer with a smal screw in the middle holding it in place. though this may be normal cause the rubber disk is plyable to pull away but pulls back into place when released. I also still have to find why i lose all my air from 120 psi to 0 after 7 hours or so. i wouldnt mind taking it in some where if they could find it & not keep my truck for days & then tell me to try it out & see how it does now ,kind of thing.

 

Relay valve.

 

They should drain at different rates. One tank is larger than the other. Now the issue is which one is draining first. If the Secondary tank (smaller tank) is draining first, then that is probably right, if the primary tank (larger tank) is draining first, then there would be an issue.

Do this test. Charge up your air tanks, make sure you know which is the primary tank (largest tank) and drain it. The gauge which still has air in it, will be the secondary tank.

Primary tank runs the rear drivers service brakes (more of them, needs more volume) and the Secondary tank runs the front axle service brakes (less of them, needs less volume)

A two way check valve connects both the Primary and Secondary tank and this gives you Blended Air which is what supplies the Spring Brakes and the Trailer Supply line.

Also, on the original question of the post, Yellow dash valve does not need to pop out on the tractor protection test to meet standards and the Red dash valve needs to pop out no lower than 20 PSI on the test.

This is the test you need to pass to stay legal in British Columbia and I think it is pretty much standard across North America, although it might be different for your jurisdiction.

With the engine off and the tanks at maximum reservoir pressure

* push both yellow and red dash valve in

(it is a good idea to have the key on (engine off) to see when your low air warings come on)

* make full brake applications until Red Dash Valve pops out

* go to the back of the trailer and make sure the trailer brakes have applied

* take off the supply line and see if there is an air leak

* take of the service line and do a full brake application to see if there is a service leak

And yes, often the Inspectors DO NOT KNOW, or will give you an opinion, of what the law is. Unfortunately they are the ones writing the ticket.