Just wonderin' if any of you could offer me an opinion about my air brake system.

On my single axle International, there's a 'distribution' valve, (for lack of knowing the correct terminology), right over the rear end, mo unted to a crossmember. All the air brake lines going to the maxi-cans and service brakes come off this valve. In the center bottom of this valve there is a screen, I believe this to be the exhaust port. When I release the maxi brakes, (push in the yellow **** on the dash), air continually leaks out of this screen/exhaust port.

My question is; do I have a bad maxi-can and is the air that's leaking by the diaphram in the can making it's way to this valve where it's escaping? Or is this 'distribution' valve itself bad? The few times I've had a can fail, it leaks right at the can itself, and I've never had one of these valves go bad, so either way I have nothing to compare it to. I really don't wanna go replacing things that ain't bad to begin with!

chaikwa.

 

Sure sounds like a bad valve. Generally if the pots leak the sound of air is right at the pot itself.

 

Sure sounds like the valve.

 

i work on a fleet of air brake vehicles. the valve you are talking about is a relay valve. sometimes these vavles can get gummed up with this "grey ooz". the relay valve can be taken apart, there is at most two shuttle valves, they have orings on the outside of them. take the valve apart and clean the pieces off with brake clean. just set the pieces out on the bench so you know how it goes back together. i have had a brake can leak back into the relay valve but this has only happened once maybe twice in six years. or you can go to a brake supply house and get a relay valve, it will probably help to take the old one with you so they can get you the right one.

 

Wow, that was fast! Thanks guys. I think Monday I'll take the valve off and go get a new one.

chaikwa.

 

when you get the relay valve off and have the new one take the old one apart. if it has the grey ooz try changing your air dryer or drain the air tanks more often...

 

Change what you will, however that is a bad maxi can, if you want to verify it, just simply clamp off the service line to each maxi can one at a time, (with the wheels chocked and the parking brakes disengaged) (yellow button in) and air system at full operating pressure (120psi), which ever side stops the leak is the culprit, period, (change the can). try it and find out for your self.

Tim

 

I dunno if I CAN clamp off the lines. They used some kinda hose that's as stiff as hydraulic line and I'm afraid if I try and clamp it, it'll stay crushed. Maybe if I disconnect it tho...

Thanks for the input!

chaikwa.

 

I have used alcohol to clean these valves before. This was out in the bush. But just take the main line from the compressor off and dump in some alcohol, start it up and get pressure up release the brakes a few times If it cleans out the gray goo, and the valve stops leaking then you know what is wrong. This is not the way to fix it unless you are out in the middle of no where and want to get home. But it is an easy and cheap way to diagnose.

 

The main air supply line to the valve should be plastic, but the lines going from the valve to the sevice and park ports on the cans are supposed to be reinforced rubber, it is actually a dot reg., and that truck could be put out of service for it if they are not. If it is an older truck and it stays local then I wouldnt worry about it. As far as damaging the lines from clamping them, wrap electical tape around the teeth of a pair of needle nose vise grips and gradually clamp the line to see if the leak slows or stops, if the line is plastic and does get damaged you can cut the bad section out and put a union in it until you can replace the line. If the line is reinforced rubber it most likely has a fiber braided jacket on it that hardens with age, (you should be able to clamp it). You can buy air brake line by the foot, maybe pick some up ahead of time, also if you want to change the lines to rubber most truck parts stores have pre made lines in stock, or they can make them while you wait. Also, under no circumstances should you disconnect a pressurized air line, (but you knew that).

Good luck, Tim

 

Agreed on the bad chamber! The diaphram in the middle is worn thru and the pressurized air is coming through the exhaust on the valve because it is trying to exhaust the air that was on that side of the chamber.