Can someone explain these brake canister bolts to me?

98G · May 28, 2015

daschae said:
The site keeps telling me in not logged in every time I try to post a reply....

He's got the socket to take those off, I will remove them and see if the brakes function properly. Do these 5 tons have the hand controller for the trailer air supply like a regular over the road tractor? So can you apply the brakes to the vehicle in tow from the tow vehicle?

with proper airlines hooked up the towed trucks brakes are applied when you mash the brake pedal.

With proper airlines applied and cage bolts removed the towed truck's spring brakes apply if your air system fails.

with proper airlines applied and cage bolts removed the towed truck's spring brakes apply along with the park brake.

the cargo trucks do not have a hand controller.

Floridianson · May 28, 2015

98G said:
While towing one truck with the other THERE IS NO REASON TO CAGE THE BRAKES!

Hook up service brake air, and emergency brake air, AND LEAVE THE BRAKES UNCAGED.

You real sure about that. If there is a hole in the spring brake pancake then it would not release no matter where the air is coming from.

98G · May 28, 2015

Floridianson said:
98G said:

While towing one truck with the other THERE IS NO REASON TO CAGE THE BRAKES!

Hook up service brake air, and emergency brake air, AND LEAVE THE BRAKES UNCAGED.

You real sure about that. If there is a hole in the spring brake pancake then it would not release no matter where the air is coming from.

Click to expand...

preface my statement with "unless there's a confirmed problem with the spring brake..."

Floridianson · May 28, 2015

Whatever but the truck is going to have one good flat side on that tire if you uncage it and tow it.
He wants to uncage the bolt and it needs to be caged don't get him off track.
If the cage bolt is snugged down it will not rattle out.

98G · May 28, 2015

Floridianson said:
Whatever but the truck is going to have one good flat side on that tire if you uncage it and tow it.
He wants to uncage the bolt and it needs to be caged don't get him off track.
If the cage bolt is snugged down it will not rattle out.

am I to understand that you advocate routinely caging the brakes when flat towing with a vehicle capable of supplying air?

bigbe5678 · May 28, 2015

Boy I wish you guys lived by me any plans to moving to New York :driver:

Floridianson · May 28, 2015

98G said:
am I to understand that you advocate routinely caging the brakes when flat towing with a vehicle capable of supplying air?

Be real. The truck has a caged brake chamber so I would bet there is a problem with the spring brake chamber. To move that truck it will need to stay caged or repaired on the spot. If it was my truck and only one chamber was in need of repair and caged I would tow it home. So of course we don't cage good brakes chambers.

98G · May 28, 2015

Let me be completely clear.

When flat towing one fully functional m939 series truck with another fully functional m939 series truck, there is no reason to use caging bolts. Connect towbars, connect safety chains, connect air lines, open the appropriate valves. You now have full brake functionality.

Assess both trucks to ensure that they are in fact fully functional. At the point that they are not fully functional, all bets are off. Best course of action would be to correct any deficiencies prior to making a 500 mile flat tow.

In the given scenario we have a truck that has a single cage bolt in place. This raises suspicion that perhaps it is there for a reason, the reason being that the spring brakes are failing to release with just air pressure due to a hole or leak. I find this plausible also. However, before assuming the existance of a leak I suggest removal of the cage bolt, application of compressed air, and see if there is a problem. If there's a problem, then consider whether to fix it or disable the spring brakes.

When you squash a family in their minivan, and then LE goes over your truck in minute detail and find nothing wrong with it except a failed air compressor and caged brakes, do you really want to explain why the brakes were caged?

Shark Bait · May 28, 2015

He'll want some type of lighted illumination on the towed vehicle too.

Floridianson · May 28, 2015

Also need to reread post #8 as this is correct. There will still be brakes applied so no mini van problems. Just no parking brakes. Hello
The OP needs help with what problem he has at hand.

98G · May 28, 2015

When air brake systems fail, the vehicle stops because the spring brakes apply.

When the brakes are caged and the air brake system fails, you have no brakes because the spring brakes do not apply.

Caging bolts only disable the spring brakes. Caging the brakes has no effect on the service brakes.

daschae · May 28, 2015

What the F is wrong with this website! My login session lasts about 5 seconds!

I have the light kit for the truck in tow. I will uncage the brakes and if they are functioning, will leave them uncaged. [thumbzup]

Dont everyone get all heated FFS, Im not trying to kill anyone with an army truck, and if you have thoughts on precautions by all means offer them, when I offer advice to someone is because Ive managed to make that mistake already, so I'm open to all input.

Floridianson · May 28, 2015

dashae I think I would take 4 new or good working order caging bolts with you just incase the ones on the truck are not there. Sometimes when the threads get wacked out and the nut jams up and is hard to turn. Also if the air leak is bad enough when you air up the truck you might have to use a pair of vise grips to cut off the air to that parking brake chamber. I bet that chamber is shot but do what you feel is right and safe.

98G if you want to nit pick then any truck that has a bad parking brake chamber and it is caged then we need to call a low boy or a tow truck that is bigger than the tow and cage that chamber to move it one foot. Bottom line. I never said you cage good chambers and dashae has only two ways of thinking if that chamber is bad. Leave it chambered and call a low boy or try to ease it home and the first being the safest way till the whole brake system is gone over.

98G · May 28, 2015

James, the main area where you and I aren't in agreement is the degree of certainty as to whether there's a problem with that chamber. Your position as I understand it is "there's a cage bolt on it, therefor it's bad, leave it there."

My position is "pull the bolt out and assess/test the brake chamber. Don't cage it for no reason."

quickfarms · May 28, 2015

98g you are wright

The caging bolts are for emergency use only, they should not be used so you can tow the truck a long distance. I only use caging bolts to allow me to load a dead vehicle on a trailer when it is not possible, or practical, to air the vehicle up. Once on the trailer we release the caging bolts.

If the CHP sees that bolt in there they will probably pull you over and do an inspection or put you out of service. They could even impound both vehicles.

One thing that I have not read is checking the brake adjustment.

For that matter both vehicles should be inspected before they are driven.

Floridianson · May 28, 2015

quickfarms said:
98g you are wright

The caging bolts are for emergency use only, they should not be used so you can tow the truck a long distance. I only use caging bolts to allow me to load a dead vehicle on a trailer when it is not possible, or practical, to air the vehicle up. Once on the trailer we release the caging bolts.

If the CHP sees that bolt in there they will probably pull you over and do an inspection or put you out of service. They could even impound both vehicles.

One thing that I have not read is checking the brake adjustment.

For that matter both vehicles should be inspected before they are driven.

No worries 98G as I said we don't cage a good can only a bad one so we can move or tow it.
Quickfarms what do they do when the big boy wrecker comes out and there is a problem with the air system or a bad can. They cage the bad one and hook and go. Now what we do is it right. Yes we do it but is it right to tow a 5 ton with a 5 ton? Do you tow a 5 ton with a 5 ton or a 20 ton. I like using my 20 ton to pull a 5 ton. Even if there was a problem with the tow brakes my 20 ton will stop the 5 ton. If you were driving a truck with caged brakes you might be looking for trouble. When a wrecker is on a call he can cage and tow. When on the hook of a big wrecker you don't want the tow parking brakes coming on while going down the road at 60 mph.
In the OP's case like I said not knowing how much is wrong with the brakes and air system the better thing to do is hire a real wrecker or low boy to haul the truck to be repaired.

quickfarms · May 28, 2015

A wrecker can not just cage and go every tow. This is reserved for really bad wrecks that are usually just towed to a safe area and loaded on a trailer.

On a modern truck the air brakes are separated into the primary and secondary system. The primary system works the rear brakes and the secondary system works the front brakes.

What they do is air up the truck from the tow truck, this is usually accomplished by tying into one of the unused tank fittings, this allows the tow truck to release the spring brakes. They them tie into the primary system using a plug that is already on the truck. If they are towing a tractor trailer they can bypass the primary tractor brakes and simply use the trailer brakes.

This is an over simplification of how they do it. The same procedure has been explained to me by experienced heavy wrecker operators on both coasts.

For safety's sake you do not want to cage the spring brakes. This can Lear to a run away truck. It is safer to have the spring brakes apply and stop the vehicle.

I know at the direction of law enforcement and under escort they can do a lot of things to get traffic moving.

fasttruck · May 29, 2015

If the caged brake is out of service because of a leaking diaphram in the emergency side then the air line leading to it from the chassis would have to be plugged to maintain the air in the rest of the brake system on both vehicles. Safest solution is either to resolve the air leak prior to departure or load the disabled truck on a trailer and these concerns can be addressed at home station.

98G · May 29, 2015

I'll be interested to see how this recovery ends up. OP, don't leave us hanging, be sure to post an AAR.

Artisan · May 29, 2015

Can someone explain these brake canister bolts to me?

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