123 Posted November 3, 2009 Share Posted November 3, 2009 When I engage the parking brake on my Mack, sometimes all the air releases through the valve in the cab. Other times it does it normally, coming out at the brakes. What's stuck that's not working properly? On a few occasions the brakes have not released properly and if I try again they do release fine. Seems to me something is kinda stuck. Any help would be appreciated, I don't know too much about air brakes, yet.... Quote Link to comment Share on other sites More sharing options...
ThaddeusW Posted November 3, 2009 Share Posted November 3, 2009 When I engage the parking brake on my Mack, sometimes all the air releases through the valve in the cab. Other times it does it normally, coming out at the brakes. What's stuck that's not working properly? On a few occasions the brakes have not released properly and if I try again they do release fine. Seems to me something is kinda stuck. Any help would be appreciated, I don't know too much about air brakes, yet....Bad quick release valves. They are designed to allow air to pass through them in one direction under pressure and when the pressure drops they open venting the air. This allows the air to vent as close to the brake chambers as possible giving you a quick response. Your spring brake quick release valves are gummed up. I don't know if you can rebuild them but I would say replace them. Quote -Thad What America needs is less bull and more Bulldog! Link to comment Share on other sites More sharing options...
Rob Posted November 3, 2009 Share Posted November 3, 2009 Bad quick release valves. They are designed to allow air to pass through them in one direction under pressure and when the pressure drops they open venting the air. This allows the air to vent as close to the brake chambers as possible giving you a quick response. Your spring brake quick release valves are gummed up. I don't know if you can rebuild them but I would say replace them.Thad is correct. Those valve can be rebuilt but it is much most time efficient to just replace them. OTC they cost about $20.00 for reman units at most heavy truck parts stores.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
HK Trucking Posted November 3, 2009 Share Posted November 3, 2009 ......and buy the metal QR valves. The plastic ones are junk in my opinion.. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment Share on other sites More sharing options...
Rob Posted November 3, 2009 Share Posted November 3, 2009 ......and buy the metal QR valves. The plastic ones are junk in my opinion..Second that one.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
123 Posted November 4, 2009 Author Share Posted November 4, 2009 Thanks! If they are gummed up, what else is gummed up that needs worked on while I'm down there? Quote Link to comment Share on other sites More sharing options...
Rob Posted November 4, 2009 Share Posted November 4, 2009 Thanks! If they are gummed up, what else is gummed up that needs worked on while I'm down there?First off I would look at the source. Your air compressor on the engine may be needing a rebuild. Once it is verified that it is either good, or rebuilt, then start taking lines loose and blowing an alcohol solution through the lines to purge them using an engine degreasing gun. These have a hose that will suck a solution up and discharge it and looks a lot like an air blow gun. Blow as many of the lines clean as you can.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
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