keg1 Posted October 1, 2013 Share Posted October 1, 2013 On my 89 R model when you step on brake pedal and release brakes don't release right away. What valve would be bad? Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/ Share on other sites More sharing options...
Superdog Posted October 1, 2013 Share Posted October 1, 2013 probably the quick release valve,either that or the foot valve is sticking,seen that happen. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209325 Share on other sites More sharing options...
keg1 Posted October 1, 2013 Author Share Posted October 1, 2013 Wheres the quick release valve at? Forgot to mention when dropping trailer and unhooking service line a little air comes out also Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209330 Share on other sites More sharing options...
Superdog Posted October 1, 2013 Share Posted October 1, 2013 the quick realse valve is usually on a bracket hanging down from the front of the rear end, the brake chambers are plumbed into it. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209338 Share on other sites More sharing options...
gearhead204 Posted October 1, 2013 Share Posted October 1, 2013 if your getting air when unhooking from a trailer out of the service port I take it that you left the supply charged {red knob pushed in} ? if this the case one of several things could be occurring 1st. trailer brakes partly applied. 2nd dirt or sunflower hulls built up under treddle valve {brake peddle} check 1 clean 2 then see what you get from service line. in the other question the qr valves are located next to the diffrentals between the air cans Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209346 Share on other sites More sharing options...
keg1 Posted October 1, 2013 Author Share Posted October 1, 2013 Red knob is out. Its not a lot of air just when you unhook gladhand a little air comes out and then it quits. I figured it might have something to do with brakes not releasing quick. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209405 Share on other sites More sharing options...
gearhead204 Posted October 2, 2013 Share Posted October 2, 2013 block the supply line and charge the line then see if you get any air from the service line. if no air apply foot brake and release see if air continues to bleed from service line after application.if air still escapes chase lines back from tractor protection valve to next valve [should be treddle valve] or possably application relay valve, if it go to a relay valve remove the control line and see if air bleeds from control line if no air replace relay valve. if air present chase control line down snd see what supplys it should be treddle valve if so replace treddle after checking for crap between valve and peddal Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209534 Share on other sites More sharing options...
keg1 Posted October 2, 2013 Author Share Posted October 2, 2013 Thanks I'll start checking it out Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209614 Share on other sites More sharing options...
farmer52 Posted October 2, 2013 Share Posted October 2, 2013 Air leaking from the trailer lines could be a bad tractor protection valve. But a leaking TPV should not cause slow brake release. Just a thought. Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-209622 Share on other sites More sharing options...
keg1 Posted October 13, 2013 Author Share Posted October 13, 2013 Have been laid up with back problems but was able to look at it Thursday night. Jacked up trailer and released brakes and they didn't release completely. Set the brakes then released again hit foot valve and still slow to release. Did it a couple more times and then they worked fine. Ran it Friday and they worked ok. I wouldn't think a valve would have had dirt or something in it because I ran it about 3 days with them dragging when I would stop. I guess i'll worry about it if they start acting up again. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-211557 Share on other sites More sharing options...
turckster Posted November 2, 2013 Share Posted November 2, 2013 On my 89 R model when you step on brake pedal and release brakes don't release right away. What valve would be bad?Only thing that comes to my mind is either the service relay valve or foot valve is bad. If both front and rear brakes are slow to release from a brake application then I would point at the foot valve, especially since when you remove the trailer service line you are getting a little air from it. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-214584 Share on other sites More sharing options...
keg1 Posted November 5, 2013 Author Share Posted November 5, 2013 Replaced relay valve on trailer. Haven't had any more problems. Thanks for the help. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-215244 Share on other sites More sharing options...
Mack Doctor Jr. Posted November 27, 2013 Share Posted November 27, 2013 The foot valve has a little cylinder under the pedal that gets dirt in it. Take the pedal off and the rubber surround to get to the aluminum cylinder and make sure it moves freely. I take them out and clean them with emery cloth and antiseize it when I put it back in making sure it moves nice and easy. Quote Link to comment https://www.bigmacktrucks.com/topic/32983-brakes-slow-to-release/#findComment-218555 Share on other sites More sharing options...
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