Lost Air - Now Brakes Jammed On

[doe70]

howdy,

just did a long trip in early r600, drained oil after first 9 hrs but then drove another 10 and no probs. today i drove 10km and rear brakes started locking on as i was starting off, are now totally locked on, ive got full tank air in starter tank but main reseviour has none. thought it was compressor dead so hooked up mobile comp in back of ute with genset, guage shows pressure rising for about a minute then drops again. ive tried blanking off comp line and acc air lines but same happens - i cant see or hear any major leaks!

have i just got oil into maxi valves? but then why no air pressure. Whats the best thing i can do, truck is on side of road still. is there an easy way to release brakes manually?

all info would be appreciated.

cheers ellis

[RowdyRebel]

howdy,

just did a long trip in early r600, drained oil after first 9 hrs but then drove another 10 and no probs. today i drove 10km and rear brakes started locking on as i was starting off, are now totally locked on, ive got full tank air in starter tank but main reseviour has none. thought it was compressor dead so hooked up mobile comp in back of ute with genset, guage shows pressure rising for about a minute then drops again. ive tried blanking off comp line and acc air lines but same happens - i cant see or hear any major leaks!

have i just got oil into maxi valves? but then why no air pressure. Whats the best thing i can do, truck is on side of road still. is there an easy way to release brakes manually?

all info would be appreciated.

cheers ellis

If you have no air in the service side of the system, your brakes will be on. The starter tank air has nothing to do with the brake system.

You CAN manually release the brakes with a bolt in the chamber....however, if you manually release them, you will have NO brakes at all (especially with no air). I wouldn't recommend doing that unless the truck is going to a shop on a hook. If you were able to build air and only had parking brakes on 1 axle of your tandems, you could limp to a shop with the brakes caged...but still not if you don't have air pressure. You NEED air pressure to apply the brakes.

If you can use your mobile compressor to air up the service tanks, and stay outside of the truck to listen for the air leak while the compressor is running. Is the air leaking when you try releasing the brakes? Or perhaps when you step on the brakes? Either of those, look & listen closely at the brake chambers...possible diaphragm broken. In my experience, a broken diaphragm will dump your air pretty quick.

If air is leaking, you WILL hear it.

Try this, too...especially if your compressor is loud (and hides the noise from the air leak)

Connect the starter air tank with the service tanks with a valve, so that you can air up the starter air tank and shut off the compressor...then use the starter air tank to charge the service tanks and listen for the leak.

[Gambi80]

If you've got a maxi brake leaking and can determine which one it is, you can cage (or back off the slack adjuster a bunch) the one and pinch off the line going to the chamber to prevent leakage and still have brakes to the rest of the truck.

If you're having trouble building air after that, use a mobile compressor to charge the air system on the truck to limp home. I had to do that when the accessory drive shaft broke on my truck, rendering the air compressor useless...if you've got a jake brake and/or not many stops it helps quite a bit.

[doe70]

Hi just an update to firstly say thanks to rowdyrebel and gambi80 for their input, helped a lot. i went up this morning in pissing down rain, hooked two air lines together and kept ute far back so noise wasnt a problem, still dumped 110psi in under a minute and half, but found it was in fact a diaphram gone in one of rears, just held rubber supply hose together and put duct tape around it few times to pinch it off. then recharged system no probs, drove home good as gold. ill get around to pulling it out and looking at it soon.

thanks again

ellis

[RowdyRebel]

Hi just an update to firstly say thanks to rowdyrebel and gambi80 for their input, helped a lot. i went up this morning in pissing down rain, hooked two air lines together and kept ute far back so noise wasnt a problem, still dumped 110psi in under a minute and half, but found it was in fact a diaphram gone in one of rears, just held rubber supply hose together and put duct tape around it few times to pinch it off. then recharged system no probs, drove home good as gold. ill get around to pulling it out and looking at it soon.

thanks again

ellis

Just be careful...them things have a lot of spring pressure in 'em, and can fly off with quite a bit of force once you remove the clamp. Luckily, the brake chambers aren't too terribly expensive...one of the less expensive things that can go wrong....and don't take all that long to change out, either

[Gambi80]

Just be careful...them things have a lot of spring pressure in 'em, and can fly off with quite a bit of force once you remove the clamp. Luckily, the brake chambers aren't too terribly expensive...one of the less expensive things that can go wrong....and don't take all that long to change out, either

Yea I worked for a guy who wanted me to change out the pancake within the chamber to save a few bucks. I told him to get phucked and if you want to do that you can handle it yourself.

[cgallamore]

Yea I worked for a guy who wanted me to change out the pancake within the chamber to save a few bucks. I told him to get phucked and if you want to do that you can handle it yourself.

i agree. a complete chamber is to cheep to risk changing a pancake, the lugs that the hold down bolt goes in corrode and give way at the worst time.