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Parking brake issue


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My 1964 B-model has roto-chambers that work the parking brake on the rear axle only. These are not maxi brakes. When i build air pressure and release the parking brake (single valve on the dash) the brakes release just fine but when I push down on the brake pedal hard, it pops the valve out. If I hold down on the foot valve, I don't hear any air leaking anywhere and I try to push the parking brake in, there is no air at the valve and it won't release. I let up on the foot valve and it works. I changed the foot valve but no luck. It looks like the dash valve is new so I'm thinking someone else tried that but no help. I'm thinking a check valve or maybe another valve somewhere is hanging up. Any thoughts?

Live every day like it's your last, because one of these days, it will be.

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  • 2 weeks later...

Ok, now that I stumped the best of you's, I think I found the problem but I for the life of me , can't figure out why. On the dash valve there was 4 lines running into the valve. Supply, delivery, a line running to a dash valve that activates the tractor protection valve and the exhaust. Someone had a line running from the exhaust to the upper half of the foot valve, so when you pushed down on the foot valve, it would pop the valve out. The problem I have is the lines is a copper line just like the rest of the lines and it looks like it belongs there. Does anyone have any idea where this line should go? The exhaust line I get, just run it outside the cab to exhaust outside. But why was it hooked up to the foot valve? Remember this truck has roto-chambers and not maxi's.

Now I know why no one had this happen to them. Someone connected the lines wrong.

Live every day like it's your last, because one of these days, it will be.

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If all else fails you can contact the Mack museum for a shop drawing of the valve that should include what lines connect to what valve.

Money, sex, and fire; everybody thinks everyone else is getting more than they are!

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