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Leaking air and oil

75 Mack

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I have a 75 f model Mack that will not build pressure. When I started looking around I found a valve under the cab at the brake pedal that was leaking air and oil. Can I just replace it or is the oil a sign of a bigger problem? Also I keep reading about air dryers on brake systems but I have not been able to find one. Are they on the older trucks?

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  • 3 weeks later...

Pictures of leaky valve will help determine what it is.

If you are getting lots of oil then compressor needs rebuilt/replaced.

Typically it is governor that is bad if it won't build presure and needs replaced.  They are cheap and easy.



1959 B61 Liv'n Large......................

Charter member of the "MACK PACK"


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I had lots of oil in my air lines, and replaced my Tuflo 450 compressor: problem solved.

I bought a re-man from Highway & Heavy Parts, as they were one of the only places I could find a Bendix compressor for a three bolt flange compressor for Macks. Priced very well too.

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