caliper brakes getting stuck

i´ve been having problems with my braking sys. cause after 1 mile my front brakes get stuck. the piping is new, pistons, seals, brake master cyl, everything is new ... and i have to bleed them to be able to release the pistons. i´m using DOT5 and if i bleed and the pistons do release means that the seals aren´t too tight, right? could it be the route i choose for the piping??? can a tight curve on the piping near the caliper cause that effect??? please let me know what you think ... cause i cannot figure this one.

gracias,

Paul. /ubbthreads/images/graemlins/driving.gif

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...the piping is new, pistons, seals, brake master cyl, everything is new...

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Does 'everything' include the hoses? I have heard of (but not experienced) internal hose failures that cause them to act as check valves & maintain pressure on the calipers.

What I have experienced that also causes this problem is a faulty restrictor valve. TR3s & TR4s have them -- only some TR4As got them. If it is there is is a little tube-like thing about 2" long connected to the top of the 4-way brake line connection.

It is supposed to act like a check valve to keep the piston from withdrawing very far from the disc and keeping the pedal firm. Nice idea until it gets gunked up and sticks. I gutted mine -- removed a spring and ball from the inside I think -- when it caused sever brake drag.

Could have possibly just cleaned it but the brakes feel fine w/o it and others recommended removing the innards.

BTW, this occurred shortly after the change to DOT-5. Maybe a coincidence, maybe not. Other than that the DOT-5 has been no trouble at all.

yep ... it does include hoses ... i dont think i have this valve but i will check it and let you know in a couple of minutes

nope there is no valve, but you know what, since the two calipers are getting stuck and overheating the rotor disks, i assume that the problem is in the master cyl, it might be a bad setting of the master cyl, í will check that. thank you for your help by the way.

Hi Paul,
Just a guess. The master cylinder piston is not fully retracting to let the line pressure vent back into the reservoir when the pedal is released. The MC linkage can be adjusted to give full retraction.
D

Paul, I think Dave is on the right page as to your problem. Just one thing, you said you have a shape bend in the line, if it's almost closed this will give you just the problem you discribe if you only have this bend on the side the brakes are sticking or are both sides doing it? Had a fellow come in with this on the rear brake and turns out he had used a pressure fitting on that curvey line on the IRS and had tightened it up so much it would press fluid into the brake but wouldn't let it out. Check master adjustment first. Wayne

So that's what that thingy is on top of the 4-way brake line connector. I'm in the middle of a frame off resto on my TR3, and last week just put in all new brake lines, and was wondering what that "thingy" was there for. It's incredible what you learn on this site.

Paul,
Another guess. As George said above, most brake systems have a "residual pressure valve - valves", (RPV). The purpose of the valve is to keep a slight pressure on the wheel cylinders, & or calipers. Disc brakes usually have a 2 psi valve & drum brakes are about 10 psi. Without the RPV, on drum brakes, there is a chance of the wheel cylinders sucking in air when the wheel cylinders retract. On disc brakes, it prevents the pads from being pushed back too far which reduces pedal height.

There is a slight possibility that your car has a RPV which is not working correctly & allowing more than two psi residual to be applied to the calipers. Not likely, but looking at all possbilities.
D

Dave, you were "right on" the first time, i bought the master cyl from ebay and it was originaly for a ford cortina ... i bought it for $30.00 brand new and the only thing i had to change was the linkage. the modification i made did not allow the piston to retract completely and this is why i was having so much trouble.

as simple as that, i so much apreciate the imput of you all ... this is why i enjoy this forum soo much ... were most of the endings are "happy endings" ...

we´re all a bunch of nuts i must say !!!!!! because of the time and energy we all put into these brits vehicles ... /ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/crazy.gif

muchas gracias ....

Paul.