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has anyone ever have your brakes not lock up but more like they're being kept on kinda like riding the brakes driving. they only do this sometimes. I've replaced everything except for drums mastercylinder and booster.
Originally posted by b.osborn has anyone ever have your brakes not lock up but more like they're being kept on kinda like riding the brakes driving. they only do this sometimes. I've replaced everything except for drums mastercylinder and booster.
thx
JBORN
Sounds kinda like your emergency brake may not be releasing completely.
Next time you give that truck a new pair of shoes, buy the brake hardware kits for all 4 corners. They are cheap, and you will be amazed how much stronger those new springs are. I once had a shoe not release and it heated the bearing up til it fried and the oil ran out turning a corner and started on fire! If that wasn't bad enough, the filler for my saddle tank was right in front of the tire. Luckily it burned itself out and I limped home. This was at the end of a 300 mile trip, and it lit up only 2 blocks from my house.
Another thing you might want to consider is the wheel bearings. Bad or improperly adjusted wheel bearings can cause a drag which can easily be confused with a brake problem.
No one has mentioned the proportioning valve. I am no expert, but the prop valve in the drum drum setup may be responsible for the residual pressure (as opposed to the master). Drum brakes like about 10 lb resudual pressure to keep em ready for the next stop. Discs need less, at 2 lb. Anyhow, it would seem reasonable to worry about it.
Next time it drags, pull over into a parking lot, jack up the front end and spin the tire. If it is dragging, reach around and ease out the bleeder. If it spins thereafter, that will eliminate lots of stuff and narrow your problem down to the prop valve, master cylinder and outside chance that the lines are full of crud. Now, if you are lucky and it does it again, the next time, do like willowbilly says and crack the line at the master. If the pressure it there, then its the MC for sure.
Since a remanded master is pretty cheap compared to a prop valve and the prop valves are hell to replace, I'd start with that.
Keep in mind, the early master cylinders had the residual valves in them, the later systems moved the residual valves to the prop valve. Somewhere, you are probably hanging up.
www.mpbrakes.com is a good resource, though the prices are otherworldly.
>so you don't think it's the mastercylinder wheel cylinders are >brand new so are brake lines .
That would be a new one on me. I've never seen a flaky m/c cause sticking. Not saying it's not possible though...The weak spring theory seems to make more sense to me if it's not a plugged line, or bad w/c. MK
Sometime if you have a leaking master crude builds up in the booster cup, and pushes the M/C piston in appling the brakes.
Check it you may have a bad M/C
Sice reman parts are marginal at best, never eliminate the source of a problem because a reman part has been installed. I agree on the prop. valve. If it is both wheels ir is unlikely to be in the wheel area but I have seen a couple times that a brake hose had internal damage and had a sort of flap in there that kind of acted like a check valve and wouldn't let the fluid return. Any complete brake job on an older vehicle should include new hoses.
Yea, if it's both, it would seem to be up from the wheels. I was guessing it was maybe just one wheel actually sticking. I've also seen the hoses do that. Normally wouldn't expect both to do it at the same time though. But you never know. It's hard to guess on the internet, when you can't see anything..
But between all the different guesses, he should get it sooner or later.
MK
I recently gave my 67 250 a brake job. The easiest thing to do is just replace everything. A master cylinder is only 24.99, front cylinders are less than $10 a piece and front brake lines are around $20 each. for less than $100, you will have a truck that stops really well.