How can I free my trucks air brakes

craigermags · May 4, 2006

To make a long story long here is my dilema.
I have a 1976 International loadstar 1700. During a pretty good week of rain, and with the hood off the engine filled with water which has lead to a stuck engine(304 CI). I am working on trying to free up the engine now so if you have some ideas on that it would be appreciated.

Failing to get it started up again I would like to relocate the truck. I can do this by pulling it with my tractor, if I could get the wheels to roll. It has air brakes, which I know little about. The brake release knob in the cab no longer has air coming into it. I tried to pull it with the tractor and it would not budge. It is in neutral so I am thinking that the air brakes might still have air in the lines keeping them engaged.

I might also add it has a two speed rear end but I did not think it would be the cause of not rolling freely.

Any help to my dilema would be appreciated /forums/images/graemlins/smirk.gif

JoshJ · May 4, 2006

I am by far no expert, but just a thought:

On some rigs with air brakes the brakes will not release until a certain air pressure is reached (for safety reasons, I presume) Come to think of it, this may only apply to the trailer brakes, but if it also applies to truck brakes then no engine = no air = its not moving. Does the compressor run off the engine or battery? (Probably a stupid question...) But if it is battery run, maybe you can get your pressure up without running engine to the point where the brakes release and you can move it.

I apologize for all the speculation... /forums/images/graemlins/confused.gif Its late /forums/images/graemlins/blush.gif

paratrooper · May 4, 2006

Here's the drill . This will apply only if you have Maxi Brakes , sometimes called "piggy back" brakes . You can tell very easy if you do . There will be 2 drum looking deals on the end of the axle . The bottom one is the brake and the top one is the Maxi . When the air is sufficient the pressure needed to release the Maxi brakes will enter the top one due to the flow from the Combination Valve . This air will depress a big spring that is forcing your brakes to stay "set". If you don't have the amount of air needed to do this your brakes will stay set . This is a safety feature since if you lose air the brakes will lock instead of as in days gone by you will lose your brakes and fly off of hills . Now for the cure . You must "cage" the brakes . There is a hole in the middle of the top chamber . If you are lucky there is a threaded rod sticking out of it . If you don't have the rod you must find one at your local truck parts store . Assuming that you have it you must take a wrench and start turning the nut so the threaded rod will start pulling out towards you . This is pulling on the spring so that it will not allow the spring to keep your brakes locked . When you have pulled both of them out your truck will move BUT you will have NO!!!!! brakes . You might want to have someone in the truck when you move it . They must have the truck in a very low gear and the clutch depressed . If control becomes compromised they will slowly let the clutch up and this will stop the truck . Hope this helps .

Stimw · May 4, 2006

As stated you probably have 2 stage air chambers on the rear axles. They used to have a slot on the side of the air chamber and the caging tool is bolted in it. The tool is a threaded rod about 6" long with a nut on one end and a "T" on the other. You put the "T" into the end of the air chamber as far as it will go, turn it 1/4 turn clockwise and pull out to seat it. Then you turn the nut to tighten it and release the brakes. NOTE!! MAKE SURE TRUCK IS IN GEAR AND WHEELS BLOCKED!! ( 2 speed axle can go into neutral, between gears and let truck roll even with trans in gear also.) Many people have been hurt releasing brakes without this step.
Another way to go is to attach a fitting to the air tank and fill with air. You could even use a cheap 12 volt compressor if you are patient. Then release brakes with parking brake button.

hudr · May 11, 2006

We always made sure we had a fitting on one of the air "catch tanks" on the truck. Mainly we used it for a source of air to run tools and inflate stuff in the field. But it also comes in handy to pump up the truck w/ a compressor and release those parking brakes.
Good luck.

Builder · May 12, 2006

Does your air brake reservoir tank have an air compressor fitting on it? If it does, you can pump air into the tank sufficient enough to allow you to release the brakes with the air brake knob in the truck.

If you don't have one, it's easy to unbolt one of the plugs on the air reservoir (usually there's 3 or 4 of them) and just thread-in a air compressor fitting. Hook up your compressor to it and pump that tank up to 100-120lbs and your brakes will be able to be released and you'll have enough air to use them a few times to move the truck around!

B safe, don't cage the maxis if they're rusted or weak, they can fly apart.

craigermags · May 14, 2006

Thanks to everyones help I now have the brakes free. Thanks

Builder · May 15, 2006

( Thanks to everyones help I now have the brakes free. Thanks )

Just curious-how did you get the brakes free? Did you pump up the air tank?

Builder · May 15, 2006

( Thanks to everyones help I now have the brakes free. Thanks )

Just curious-how did you get the brakes free? Did you pump up the air tank?

craigermags · May 24, 2006

Finally got the air brakes fooled by hooking up my air compressor to the air chamber tank and then releasing the brakes as usual. /forums/images/graemlins/grin.gif