FMTV Refuses to charge air from front emergency gladhand

[NDT]

Does your truck have this malady? You connect an air supply to the front emergency glad hand, hoping to get brakes up but no air makes it to the tanks. In the case of my new 1081, the culprit was the one way valve right behind the middle of the front bumper. You can remove it without pulling the bumper by working through the air slots. Fortunately this is a super common heavy truck part, just bring it with you to the heavy duty parts counter. Someone must have left the glad hand cover off, and rain had entered the glad hand and ran down to the valve, freezing it solid.

 

[Suprman]

That will cause your brakes to lock up same as a blocked gladhand will too.

 

[Floridianson]

That will cause your brakes to lock up same as a blocked gladhand will too.

Will do believe he is talking about the emergency front line that needs the one way valve. If it was not there then the air tanks could drain if the check valve was not there. Do believe the service front line does not have a one way valve. When the brakes are applied by way of the treadle valve the rear service line is under air charge. When the air brakes are released then the whole service line is allowed to evacuate and that is why we check for the little breather on the glad hand service line. If that does not work then the charge from when we applied the brakes does not clear the service line.

 

[Suprman]

The front emergency glad hand needs to be able to breathe. Being blocked can cause the rear brakes to not release. That check valve is a bit towards the passenger side below the bumper. Both gladhand covers have breathers on them.

 

[Floridianson]

If the front emergency glad hand has a one way valve then it is air in only not out. We charge the tanks with that not the brakes. The line you are talking about is on the other side of the T block and vents. The one way valve is on the other side of the T block and goes to the tanks. That is why there would be a vent on the front glad hand. The post is about the one way valve being rusted shut and not taking air.

 

[Suprman]

 

[Floridianson]

Yes the vent has to work on the emergency glad hand. I add to my post about the T block but you type faster than me. The one way valve is on a T block. One side charges the air tanks and only goes one way. The other side of the T block has the vent line from the brake system. Go look at it and you will see the T block.

 

[Suprman]

Yes but the first thing one of the mil mechanics showed me on the LMTVs is that check valve and was very clear its one of the first things to check when your brakes won't release. He actually carried a spare in his pocket.

 

[DSD277]

NDT is referring to the one way check valve in the other gladhand line, and it is to charge the air tanks. There is a 'T' in the line and the other leg goes to a two way valve behind the driver step.

 

[Floridianson]

I got a pic. See the T block the one way valve is on the right and has nothing to do with the brakes releasing. The line on the other side is the vent and is open to the glad hand and its vent.

 

[Floridianson]

I carry a mouse around it my pocket but I don't know why.

 

[Suprman]

So many different check valves.

 

[gimpyrobb]

What?

 

[Floridianson]

So many different check valves.

That is the truth. Yes as you said both emergency and service glad hands must have the vent. Both need to be working. This is why I like the older systems in the 809 and in the Deuce so much less to track down.

 

[Feal318000]

the check valve in the pic that floridianson posted is the one that would be behind the grill on the left side. that check valve is fairly easy to remove and clean. i was getting a real bad air leak out one of the front glad hands, so i disassembled it, cleaned it, and reinstalled it.... no more leak. to me- that check valve (if front glad hands aren't used frequently) is basically a dead end for grime, rust and debris in the air system to get caught up in.

 

[NDT]

New one, Velvac 320014, $17 bucks.

 

[Floridianson]

Think the confusion was on the two check valves. The PM is talking about the check valve on the glad hand cover that is like the one on some of the axles that only vents out. Then the bigger check valve that protects the air tanks. So this was a good thread about keeping the glad hand cover vent open for the parking brakes and the one way valve for the air tanks that can get locked up or leak back through the glad hand cover.

 

[bakerdude]

the check valve in the pic that floridianson posted is the one that would be behind the grill on the left side. that check valve is fairly easy to remove and clean. i was getting a real bad air leak out one of the front glad hands, so i disassembled it, cleaned it, and reinstalled it.... no more leak. to me- that check valve (if front glad hands aren't used frequently) is basically a dead end for grime, rust and debris in the air system to get caught up in.

Thank you for bringing comments all

the check valve in the pic that floridianson posted is the one that would be behind the grill on the left side. that check valve is fairly easy to remove and clean. i was getting a real bad air leak out one of the front glad hands, so i disassembled it, cleaned it, and reinstalled it.... no more leak. to me- that check valve (if front glad hands aren't used frequently) is basically a dead end for grime, rust and debris in the air system to get caught up in.

Thanks, bought 4. After enlarging the pic, I might even be able to make the switch. I was not looking forward to removing the massive bumper and all 20 some bolts, not having an impact tool. Peace

 

[Mullaney]

New one, Velvac 320014, $17 bucks.

.
THANKS for the part number NDT !

I just ordered several so I can replace mine.
If the old ones clean up, great. If not, at $17 I can still smile

Bumper is already off on my M1089, so it should be a breeze for one...

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Thanks for sharing Floridianson

I appreciate the info and discussion!

 

[olly hondro]

I deleted the one on my truck, along with it's three trouble-making brothers behind the driver's step.