75 Mack 6 Posted October 20, 2018 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? Quote Share this post Link to post Share on other sites
Freightrain 2,385 Posted November 8, 2018 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. Quote Share this post Link to post Share on other sites
brickhouse15 12 Posted November 8, 2018 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. Quote Share this post Link to post Share on other sites
