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I loose all my air when I set the park brake on my 1972 Prevost. It continually blows out the relay exhaust valve. Brakes work fine, if I don't set brake air holds up good.
I have a 1967 Silver Eagle Bus that I can not get the maxies to release On the rear drive axle. Is there any way to manuel release the maxies. Please Help ??????
Does this unit have spring brakes or cam locks, some "early" Prevost cars were delivered with the DD3 cam lock pots instead of 30-30 spring pots. Most bus companies at the time were running GM and MCI with this equipment and prevost would give you what you want.
If it has DD3's the air system aplies air to lock the brakes in the park position, there are protections in the system to insure that it will work if the rest of the coach looses air. the DD3 has an apply diaphram and a park apply diaphran as well as a cam release sysetm operated by air. maxi or spring brakes have 2 (two) air lines, DD3 has 3 (Three) going to it. If DD3 type tear off the top and replace the damaged diaphram, $110. last time I bought one, $440. for a rebuilt pot.
If its got 30-30's on it you have a relay valve problem probably, I hope.
The air is blowing out the exhaust valve part of the relay valve that connects between the maxi brakes on the drivers. This happens when I set the park brake.
That's interesting, as all that's supposed to happen when you set the parking brake is that the air pressure is exhausted in that section of the "can" that holds the spring brakes off. When you hit the "park" control the air is dumped, and the spring activates the foundation brake, setting them.
Sam,
That's right, the air is suppose to exhaust from the maxi and set the spring brakes. However, the relay valve that has the exhaust port for the maxi brakes to exhaust continues to exhaust air and drain the system. If I hold the part brake in the released position it stops exhausting and air build again. After I have been stopped for a while and the air bleeds off I start the engine and hold the part brake in the released position and air builds rapidly.
I have a 65 silver eagle bus.
I was getting oil in my air system. So I changed out the 501 bendix compressor and the type 2 governor. The system will only get 50 psi I've checked for air leaks and have repaired two with new lines. Any sugestions of what I may need to check. I thought about checking the check valves in the system but all are hard piped in and if I break them apart I will not be able to align the fitting up to reinstall.
The manual stated that I should have 5 air tanks I've have only found 4 I think when they converted the bus to a motor home one was removed that was used to operate the door.
Any help with this problem will a blessing.
email Roger
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