ranchhopper Posted March 6, 2018 Share Posted March 6, 2018 For some reason the center air valve (yellow) leaks when its cold does anyone else have this problem? Its only below 40 or so degrees leaks pretty good out of the bottom where the exhaust port is the brakes do release but the light does not go off charges a full 120 PSI but gets pretty irritating. Quote Link to comment https://www.bigmacktrucks.com/topic/52723-air-valve-leaking/ Share on other sites More sharing options...
Rob Posted March 9, 2018 Share Posted March 9, 2018 (edited) Pretty common once the valves are a few years old due to the hot/cold cycles the cab endures. I think it's an "R7" valve but you'd need to check as I've been away from trucks for a while. O ring kits are cheap but the valve is usually about $20.00 so not really worth rebuilding, (to me) locally. Sorry for my inaccurate post but the valve is either a PP-1, or PP-7 and not an "R-7" as I posted earlier. R-7 is a relay valve. PP-1 is the most common to release tractor brakes and PP-7 is for charging semi trailer brakes. Edited March 12, 2018 by Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/52723-air-valve-leaking/#findComment-393729 Share on other sites More sharing options...
other dog Posted March 10, 2018 Share Posted March 10, 2018 19 hours ago, Rob said: Pretty common once the valves are a few years old due to the hot/cold cycles the cab endures. I think it's an "R7" valve but you'd need to check as I've been away from trucks for a while. O ring kits are cheap but the valve is usually about $20.00 so not really worth rebuilding, (to me) locally. that may be true, but what I usually do is just grab the valve and wiggle it back and forth a few times, that will usually stop the air leak. Hi Rob! 2 Quote Producer of poorly photo-chopped pictures since 1999. Link to comment https://www.bigmacktrucks.com/topic/52723-air-valve-leaking/#findComment-393788 Share on other sites More sharing options...
Rob Posted March 10, 2018 Share Posted March 10, 2018 Hi Tom; Most of those valves only leak during the cold months and are perfectly silent during the warm summer season. I have several in my parts bin of all types and one of these days when I start working on trucks again, I may use a few on a couple projects..... Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/52723-air-valve-leaking/#findComment-393816 Share on other sites More sharing options...
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