Skip to main content

Site Navigation

Your Account

Choose Language

Why is air backfeeding from my trailer emergency supply line?

My trailer is back feeding through the emergency (red) air line when I set the parking brakes. The air was feeding through my red brake knob on the dash, so I disconnected the red air line and air was pouring out of the trailer gladhand. In addition, when I set the trailer parking brake only, it is slow to apply, by this I mean several seconds from the time I pull the valve until the truck stops rolling. I'm thinking one of the trailer valves would need repair, a friend suggested the dash air valves, as air comes out of the valve as well when it's set.

I have a 2012 GD air ride trailer that has Heindrick air ride suspension. I only have one air tank on the trailer, and a valve in front of it that has a controller on top of it for the ABS system. There is another valve behind the air tank, that I have found some air exhausting out of as well, but seldom does air come out of this valve. Which valve do you think is bad? Do you think I can take it apart, clean it, and put it back on? Or do I need to replace it? What about air system conditioner, isn't that just alcohol? Would that do any good?


OK, what it turned out to be was the air slider button/valve.

All the brake chambers tested good, and the valve did as well. I took it to a mechanic at Cowser Tire & Service, they replaced the service air valve, but that didn't fix it. They had already checked the brake chambers so the said they didn't know what else to do. They had put the new air valve on, and worked on it for a couple of hours, but didn't charge me anything as they weren't able to fix it.

Then I went to Great Dane in Dallas. They said it was the air valve, but Cowser had put on the wrong air valve so GD replaced it again. This still didn't work, they also had checked the brake chambers, so he closed off the air slider hose, which made the brakes work as they should. So they replaced that button, which, the part was $33, and it worked. The total charge was $233.61. They said the valve that was put on was not OEM so that's why it was replaced first, and they had never seen the air slider button/valve cause this problem before. As all the chambers tested good, so the valve was the obvious culprit at that point. All in all, I'm happy with the result, I learned that the air slider valve button, can cause back feed through the emergency glad hand, and how to test it.

Answer this question I have this problem too

Is this a good question?

Score 1


I don't hear a leak from any of the chambers. How would one determine which chamber is bad? This certainly would be better than the valve which I was told would be $800 to replace.


Add a comment

3 Answers

Most Helpful Answer


I tired to send you the complete test including checking valve KR web site wouldn't let me if you need it I'll try sending it again let me know

Disconnect Delivery Line to Service Side of Spring Brake Chambers, one at a time. If there is a leak out of the Service side of the Spring Brake Chamber, replace Spring Brake Chamber (Remember, there may be more than one bad chamber). I hope this makes sense to you. You have two lines going to each of the 30/30 air brake chamber one going to be able service and the other one will be labeled emergency

Was this answer helpful?

Score 3


My easier way to do this test is to purchase a pair of 10" Radiator Hose Clamping Pinch Off Locking Pliers, and clamp off the supply line to each chamber. If the air stops, that's the leaking chamber.


Add a comment

You have a air brake chamber that's bad on the trailer

Was this answer helpful?

Score 1
Add a comment

I do not believe that you have a brake chamber problem. As new as the trailer is I doubt the brake chambers are failing. Most of the company trailers that I pull that have this problem they usually replace the ABS computer valve.....don't know the exact name or the number of the valve but it seems to be a common failure on these trailers. There is a quick release valve on the trailer too that can go bad.

Was this answer helpful?

Score 0
Add a comment

Add your answer

Steve will be eternally grateful.
View Statistics:

Past 24 Hours: 15

Past 7 Days: 112

Past 30 Days: 486

All Time: 20,598