M939A1 Spring Brake Reservoir Cut-off Valve and One-way Valve location?

[Bonte]

EDIT: Found the problem! The one way valve was installed BACKWARDS. This had the opposite effect obviously and instead of preventing the spring brake reservoir from back feeding into the secondary reservoir, it prevented the spring brake reservoir from filling!

Will solve the problem tomorrow when I get the right tools for the job.

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Greetings,

I found my spring parking brake release valve (dash valve) to not be operable when I acquired my M934A1 truck. I also found that the drain for the spring brake reservoir is always empty (drain #4) which leads me to believe that no pressure is making it from the secondary reservoir to the spring brake reservoir or there is a serious leak somewhere. I am unable to detect a leak and my secondary tank takes a looong time to drain, so I do not believe that to be the case.

Since there is no pressure in the reservoir and no back pressure on the valve, I am assuming that either a cut-off valve has been closed between the secondary reservoir and the spring brake reservoir OR the one-way valve between the two has failed somehow or was installed in reverse.

First question, is there a cut-off valve for the spring brake reservoir? I am getting mixed information from the operators manual and the technician manual about the existence of such a valve. The parts manual does refer to a valve, but I could not find it in the TMs or in any figures in the operators manual. If it does exist, where is it located?

The second is the location of the one-way valve which is between the secondary reservoir and the spring brake reservoir. This is shown in the technician and parts manual clearly but I am uncertain where exactly I can find it so that can test it for damage. If a cut-off valve does not exist, or it is open - this could be why I do not have any pressure in the spring brake reservoir.

Thanks in advance for the assistance,

Bonte

 

[73m819]

That dash push valve is the emg. override, in normal operation, it is OUT, the emg. brake handle controls the normal spring brake operation though a air valve that is controls.

 

[Bonte]

That dash push valve is the emg. override, in normal operation, it is OUT, the emg. brake handle controls the normal spring brake operation though a air valve that is controls.

Yes, I am very well aware of the operation and function that the spring parking brake release valve and the position it must be in to operate. However, my spring brake reservoir never fills and thus the valve will not function which is the reason which prompted my question.

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