ozrad7 Posted April 7, 2010 Share Posted April 7, 2010 Im just wondering if it is normal for there to be a delay between when the front drive brakes lock up and the rears do? mine seem to take a good 1-2 seconds or depending on adjustment dont lock up at all. I only noticed this because sometimes part of the load gets stuck in the tipper body and needs a bit of a jolt to get it out. The truck is a 84 r688rst with 55k rear end. Quote Link to comment https://www.bigmacktrucks.com/topic/13326-r688-rear-brake-question/ Share on other sites More sharing options...
Packer Posted April 7, 2010 Share Posted April 7, 2010 Sounds like an air volume issue.Kinked line, junk in the air line, maybe a stuck valve??The brakes should all be working with very litle lag in them.VERY little!Look for a dent or kink that reduces air flow to the rear brakes.If flex hose is involved, you may have the inner lining peeling back and plugging the line.Are the linings wearing the same?Has this issue just started or has it been there awhile??Air brakes are the best system trucks have.Electrical and mechanical are the ones that pop up the most.I think that you will find that the problem will be simple and easy to fix.Finding it may take a bit.Packer Quote Keep a clutchin' Link to comment https://www.bigmacktrucks.com/topic/13326-r688-rear-brake-question/#findComment-52638 Share on other sites More sharing options...
ozrad7 Posted April 7, 2010 Author Share Posted April 7, 2010 its been like it since ive owned it so 9 months and for how long before that is anyones guess but the drums and linings were replaced before i bought it, i did have to replace a slack adjuster on the rear drive as it would loosen itself off within a day or so.I just put a new compressor on it and there was a lot of oil in the air system which seems to have cleared out of the tanks now so maybe the lines,valves, ect. all need pulling apart and cleaned out. I need to do the wiper motor aswell as it wont work until the engine bay warms up. I didnt want to touch the brake system until i was sure i had a problem. Quote Link to comment https://www.bigmacktrucks.com/topic/13326-r688-rear-brake-question/#findComment-52639 Share on other sites More sharing options...
spud Posted April 8, 2010 Share Posted April 8, 2010 sounds like a lot of oil has got into your air system mate! pour some metho in your wet tank and into your maxitorqe filters it should work .we had the same problem on a v8 valueliner "crook aircompressor" other than the first option the only other alternative is too take of your relay valves and clean them out. Quote Link to comment https://www.bigmacktrucks.com/topic/13326-r688-rear-brake-question/#findComment-52725 Share on other sites More sharing options...
ozrad7 Posted April 9, 2010 Author Share Posted April 9, 2010 yeah im not getting oil from the tanks anymore so whats in the system would be built up sludge i think, when you put the metho in the system how long do you leave it in for before draining the tanks? a day or two or a couple of hours and repeat till it starts coming out clean?.My local truck work shop told me all they could do was remove all the lines and tanks and clean them seperatly to which i said dont worry about it. Quote Link to comment https://www.bigmacktrucks.com/topic/13326-r688-rear-brake-question/#findComment-52780 Share on other sites More sharing options...
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