air brakes leak

[Utahclaimjumper]

Robert,, Mike will be at "Q" and has the same setup as yours. He has changed his several times and knows them well.>>>Dan

[eagle19952]

Yes I have a 1962 4106 with I think they are called mini-max cans, there is one hose from the valve on the bulkhead to the can, the diagram is 6 inches and is connected with a two bolt clamp. I am on the road now hopeful I get some insight at the Western GM rally at Quartzsite. Happy New Year to all.

so with one hose it is not a parking brake

it can only be an application brake.
the leak returned and it is strange only leaks when parking valve on, something big leak other time small. no loss of air with parking valve off.

which makes me wonder if the relay valve that feeds that brake isn't plumbed wrong..or is defective.
does the pedal actuate the can ?
it's a head scratch that won't be solved without eyes and hands on .

[Jim Eh.]

Caution: To anyone that does NOT know - spring brakes can be deadly. Be sure you know what to do before attempting to alter or repair your brake chambers!

If you only has one hose going to the brake chamber, it must be a pre 121 system? If that is the case then it is most likely leaking when the brakes are applied as well. it could be that the diaphram is just not seated correctly and the is leaking. With no air applied (make sure the bus can't roll while you are under there) you could try lightly tapping all the way around the clamp as you apply a little torque to the clamp bolts to help seat the clamp.

Does it look like this?
http://www.fleet-products.ca/3000sc-type-30-service-chamber/

[luvrbus]

Just 1 line he has ICC brakes

[buswarrior]

Yup, what luvrbus said.

Air applied using a hand operated control knob or lever style control.

Still only one diaphragm back there, activated by two paths of air further up the plumbing...

The chamber will be leaking under a brake pedal application too.

make it stop before you go.

happy coaching!
buswarrior

[eagle19952]

Caution: To anyone that does NOT know - spring brakes can be deadly. Be sure you know what to do before attempting to alter or repair your brake chambers!



Does it look like this?
http://www.fleet-products.ca/3000sc-type-30-service-chamber/

ONLY IF THEY ARE TWO CHAMBER. This one can hurt, a lot.

except the new ones have a band that cannot be removed. you really have to work at it to hurt yourself with the new style,




it's the back chamber spring that gets you. the front service chamber...no big deal about as much tension as an ink pen spring. ok a bit more, not much more tho.

[Jim Eh.]

If you are working on a single chamber, have someone apply the brakes or set the "parking brake" (I used that term loosely) and clamp the pushrod with a pair of vise grips. Then release the application or "parking brake". It will keep the pushrod plate out of your way so you are not fighting the light return spring when reassembling the brake chamber. Once the clamp is back in position release the vise grips and test for leaks.

I once saw a loaded fuel tanker start rolling backwards in the parking lot of a truck stop when the air system dropped on a pre 121 system. Only the trailer brakes were set to "park". It looked pretty funny watching an old guy running after that truck. I dared not laugh at "the driver". Dad would have kicked my butt for the rest of the trip if I had. For the rest of my life I thought of that moment whenever I saw a Bendix RE6 equipped brake system.

[luvrbus]

Some GM owners get creative and just add a PBV to the ICC system and when the air leaks off they have no parking brake so they keep their mechanical parking brake with the Johnson bar