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1993 Mack MR


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Air builds very slow.  


I'm refurbishing this truck that my sons were going to put in the bone yard. They said it had bad tranny.

I got it going real good, eat on fuller road ranger, up shifting with full load, back brakes were sticking to start but freed up.

The next day, no shifting, found bad dual check valve from primary and secondary tanks . Air left that valve to back brakes and tranny

Installed new check valve now shifts great and port at tranny reads 75psi, but brakes appear to stick and air builds very slow.

And when hits 120 blows off ok, but when I push the maxi in, both tank gauges drop 15psi.

Where should I start? Unloaders in compressor? A friend told me years ago that building air slow could be fixed by turning some set screw on governor and that something was getting stuck

Does anyone know what the flashing light is? Reverse with pic of truck





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