How To Release Breaks Without Caging Them?

[Rob]

Here is a question that is real and not hypothetical:

Let's say you have a tractor with low batteries and no jumper cables handy. There is also not enough air in the receivers to release the spring brakes so the truck could be push started. There is also no air fittings on the tanks to connect a shop air line to. I've been told you can charge the air through the glad hands but I've tried and could not get the truck to charge. I tried hooking lines service to service, emergency to service, floored the brake pedal with each event of the dead truck, then even tried holding the protection valve in to no avail.

Am I missing something? Once I swapped batteries, and the truck started right up, it readily made air quickly.

Rob

[peterj]

I'v been told that too, I'v never had any luck doing it. I usually put a quick connect in the wet tank drain, and plug on the shop hose... For a one time deal, a blow gun with a rubber tip, into the petcock.

[Lmackattack]

on older trucks it was possible. I think the problem with new trucks is the tractor protection valve??? If I recall you could hook air to the red hose. push the valve in and air could be put into the emergency tank to charge?

With new trucks if its not the Tractor Protection Valve its the check valves thru the system that dont allow this. They obviously only let air flow one way. It shuts if air tries to flow back to the tank. Rob on the RS macks I put a air tool fitting on the wet tank. I can charge it with shop air if I want to move the truck without waiting for it to charge. a monkey wrench and a air tool fitting is all that is needed (besides the air!) Works great.

[Lmackattack]

Could also back the slacks all the way off so the shoes dont contact the drums

[Rob]

Hi there, this truck showed up last evening with a dead shorted battery so it would not take a jump, and the truck was without air in the tanks. No air fitting anyplace. I have air fittings in all other trucks so I don't need to wait for them to air up and can move quickly. This one will get one also but I couldn't get it off the trailer. Cause the brakes could not be overpowered without breaking something. I grabbed fresh batteries from my "yella dog" and it started right up and released the brakes without problem. I've just been told you could charge from another truck through the gladhands so I figgered I was doing something wrong.

Thanks,

Rob

[Packer]

A glad hand and an air hose chuck and an air line would work.

Glad hand with air line quick conect.

Air hose and another quick connect in the air tank.

Hook them all togother and then switch the valve in the 'Jumper' truck.

Trucks with air-start all had that in the tool box (in the day).

Packer

[Rob]

Using a gladhand and air chuck to charge another truck's wet tank I do almost everytime I want to move something around here. This new R612 had no Schrader valve fittings anyplace on any tank. This is why I wanted to charge through the gladhands. There was no combination I could think of to make it work. If I could have released the brakes the truck would have rolled two feet and started.

Rob

[peterj]

Sometimes they put the schrader valve in strange places... My H , has it way up under the dash.. I didn't see it till I had the dash out, and you couldn't put a long air chuck on it anyway...

[ThaddeusW]

on older trucks it was possible. I think the problem with new trucks is the tractor protection valve??? If I recall you could hook air to the red hose. push the valve in and air could be put into the emergency tank to charge?

With new trucks if its not the Tractor Protection Valve its the check valves thru the system that dont allow this. They obviously only let air flow one way. It shuts if air tries to flow back to the tank. Rob on the RS macks I put a air tool fitting on the wet tank. I can charge it with shop air if I want to move the truck without waiting for it to charge. a monkey wrench and a air tool fitting is all that is needed (besides the air!) Works great.

That is the problem Trent, The air brake system has check valves all over the place. The tractor protection valve should allow air to flow back via the emergency line and so should the dash valve. But there is a check valve between that line and the air tanks. Its a double check valve that allows both the primary and secondary air tank to feed the trailer while also isolating the two circuits from each other. And the spring brakes are fed from one of those circuits through a relay valve and possibly a spring brake valve.

Rob,

I would consider outfitting every truck with a schrader valve or better yet, an air line quick coupling or even glad-hand along with a check valve for safety. But then again I am pretty much preaching to the choir at this point

[Rob]

That is the problem Trent, The air brake system has check valves all over the place. The tractor protection valve should allow air to flow back via the emergency line and so should the dash valve. But there is a check valve between that line and the air tanks. Its a double check valve that allows both the primary and secondary air tank to feed the trailer while also isolating the two circuits from each other. And the spring brakes are fed from one of those circuits through a relay valve and possibly a spring brake valve.

Rob,

I would consider outfitting every truck with a schrader valve or better yet, an air line quick coupling or even glad-hand along with a check valve for safety. But then again I am pretty much preaching to the choir at this point

No problem Thad. What I actually do is install a ball valve into the tank. I then install a quik disconnect air fitting into the ball valve. This flows air and charges the system quickly as there is no valve core for restriction. After the system is aired up, shut the ball valve, and remove the air line.

This latest truck is the only one that doesn't have the setup, yet.

Rob

[Greg Rider]

I don't think that air will flow "backwards" through the system. Some older trucks that had air to hold the brake vs a spring could be backfed. I would have tried to adjust the rods as stated before till they released enough. Cage bolts are handy though!

[dak49]

Here is a question that is real and not hypothetical:

Let's say you have a tractor with low batteries and no jumper cables handy. There is also not enough air in the receivers to release the spring brakes so the truck could be push started. There is also no air fittings on the tanks to connect a shop air line to. I've been told you can charge the air through the glad hands but I've tried and could not get the truck to charge. I tried hooking lines service to service, emergency to service, floored the brake pedal with each event of the dead truck, then even tried holding the protection valve in to no avail.

Am I missing something? Once I swapped batteries, and the truck started right up, it readily made air quickly.

Rob

Rob, with some of the older trucks you could hook both the emergency lines together and usually it takes 2 people to do it cause BOTH valves have to be held in at the same time, with the newer trucks, mostly after 1975 its not possible to do that cause they have some thing in the line that keeps air from going back into the air tanks. I carry fittings so if I ever need to have that done I just pull a plug on an air tank and I have an air hose I connect to the emergency line to air up tires, then I can either use my hose to air up my truck or some one else's. If I let some one use my air tank fitting after we get it started I have them pump down the air so I can remove my fitting, replace the plug and they are ready to go, well after they get their air back up again. IF YOU TRY that, be sure they have very little, to no air before you remove the air fitting, you don't want to get hurt trying to take it out. Oh, yeah, I always put a valve stem in an air tank on any truck I drive just in case I need to air it up and go.

Good Luck,

Dak49

[rhasler]

IF YOU TRY that, be sure they have very little, to no air before you remove the air fitting, you don't want to get hurt trying to take it out.

Nor do you want to get sprayed with decades worth of compressor pumped engine oil that may be residing in the air tank!