Ok , I need a little help here. I have disc's on all four corners & a firewall mounted booster/proportioning valve on my truck. Problem is the front brakes are sticking. Bled the brakes last week and have good pedal pressure but the front brakes don't seem to be disengaging. Any ideas?
Got a bit of freeplay in the pedal pushrod? Is the booster pushrod a bit too long? Newer front brake hoses?
If you happen to have the wrong master cyl (drum brake) it will have a higher residual (holds a little pressure in the line, like 10psi on drum brake master vs 2 psi for disc) Just a thought
I think he's likely onto something here. But doesn't it seem like the rear discs would be hanging up instead of the fronts, ***uming he's got a front disc/rear drum master cylinder? I've had front discs hang up with old brake hoses where the inner lining of the hose had deteriorated and acted like an internal check valve. Maybe a little strange to have both fail that way at the same time though. Try pumping them up so they stick again and crack a brake fitting somewhere between the front hoses and the MC (not at the caliper) and if the wheel still drags suspect the hose. If the wheel releases then the problem is elsewhere in the system.
Do they stick when they are cold or just get worse when the cars been driving for a bit? Pull the master and make sure that the snap ring that holds the pushrod in place hasn't twisted a bit. That happened to me once. Because it twisted, it didn't allow the pushrod to fully disengage. When the brakes were cold, it wasn't noticeable...but that little bit of drag on the pads would cause the fluid in the calipers to expand because of overheating and that would cause the brakes to stick.
You are right, the rears would be hanging up too, unless the china man who put the master together only got one in wrong. More likely something else. Depending on which way you have it plumbed, the rod being adjusted a little too long might lock up one set.
Isnt that what a brake proporting valve does ? Less presure to the front and more to the rear,or vice,versa depending on car/truck and master cyl...................YG
I was having the same problem, I changed the valve and problem solved, make sure you have the right prop. valve they look the same but could be different, They make them front disc and rear drum and one for all 4 disc.
I used drum brakes on a 67 b,cuda i raced and bought a adjustable pro,valve and adjusted the front brakes hard so i could do burnouts with less strain on brakes on rear.Worked great,maybe that might help fix her if everything else ck,s out ok..........good luck..............YG
I don't think it's the M/C. It did the same thing last year when I had it running briefly. All components were new, including the hoses and calipers. It has sat up however for a number of years as I piddled with it. As I mentioned before I just swapped out the M/C recently. It's the same style but it came with a proportioning valve. I think the calipers have gone bad from sitting so long. Just bought a set to install but got side tracked by my dog. He got out of the yard yesterday morning and was missing all day. He came back home that evening and was is awful shape. Looks like he was attacked by a pit or two. There are huge chunks missing from all four legs with his back legs being the worst. His face is all torn up as well. Gotta play doc for awhile.
Pump up the brakes till you get them to stick, go to the bleeder valve on the M/Cyl, crack it, if you get pressurized fluid out of the bleeder on the M/Cyl then you know for certain the residual presure relief in the M/cyl is holding too much pressure. It may be bad or just not for that application. It is the little Br*** seat the Line seals against when you screw it into the M/cyl, easyst thing is to replace the m/cyl but if you can find a knowlegable parts man in a brake specialty store he can sell you what you need the little valve can be pulled out with a screw if you know how to do it. or let them do it for you.
If your new m/c and proportioning valve are for your truck or one very close in weight,you are likely ok.BUT if its for a car or truck that weighs 700-1000 lbs less you could have problems you cant fix.Ive been told by master mac ,that weight doesnt have a thing to do with a master cyl.If it doesnt then why would they have so many diff typs and sizes.IOW A dump truck wont use a vega m/c or VW.Just trying to explane the point.Good luck.......................Let us know...........YG
Problem solved!! Got a chance to install the calipers and that took care of the problem. Now on to the engine. Gotta figure out why it's running so ****py!
Great news,thanks for the update,engine running ****y? ck air in tires?......just kidding. hope its a cheep simple fix.......................YG
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