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Air line problems

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Ever since I bought my RS700L I have had parking brake problems both the release valve and distribution valves on the driver side frame rail were replaced. I replaced both valves when I bought the truck with valves from my parts truck. The original valves were broke off the frame that's why they were replaced all airlines were swapped to the same ports on the valves they were taken from. Now the problem is there is a delay when pulling the valve out to set the parking brakes there is a noticeable sound of air being forced somewhere I don't believe it should be when pushing in the yellow release valve there is a noticeable hiss of air behind the dash somewhere by the release valves on the dash which quits after 6-8 seconds but does drop the air pressure gauge quite a bit. The distribution valve on the frame leaks all the air from the tanks within an hour after parking the same as it did with the old valves that were replaced. When pushing in the blue tractor brake valve on the dash it is being held out by air pressure it wont stay pushed in the release position the only valve that will stay in to release the brakes is the yellow valve. I would like to eliminate the extra release valves in the cab because the truck is no longer a semi tractor its just a straight truck now any suggestions would be helpful something is routed wrong somewhere..

Edited by ranchhopper
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When I set the maxi brakes on my trailers I have the same thing. A long drawn out hiss of air. I believe there is an exhaust valve beneath my Suzy hoses. I'd guess there might be an exhaust valve somewhere in your truck system that might be dicky. 

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You can take a look at page 31 or 84 in the Bendix link and this may give you an idea of what is in a single yellow knob set up.  Also, using the Bendix book, you could check your existing system versus their schematic for an explanation on what is going on with your truck.


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It doesn't cost anything to pay attention.

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