vip3r82

I am at a lost!
Both old and new cal are locking up, no ABS light, bleed all my lines 4 times or more. cal sliders are greased and working fine. I don't have a way to get to shopkey5 at this time and must get this fixed asap!
Any and all help would be great!

Thanks!

BabyGT

Line might have collapsed internally creating a sort of check valve letting pressure get to the caliper but not push back the other way through the line causing it to stay locked up.

TfcCDR

There are check valves in the system, at least one for front and one for rear. They're not actually "check" valves, they are there to add resistance to the backflow of fluid, so that new fluid will be drawn into the system from the reservoir. All of them that I have seen were at the master cylinder. It's possible that a "performance" car will have valves at the brake block, too.

If the valve fails (or is clogged by gunk), fluid pressure won't drop as fast as it should when the pedal is released, and the driver's side brake will be affected first (because the line is shorter).

My first thought was water in the brake fluid, expanding and applying brakes, but the OP said the fluid has been changed several times. Assuming that this wasn't done out of the same (possibly polluted) can, it could be that water is trapped in OLD fluid in the caliper of one or both front brakes.

vip3r82

Here is what i have done so far.
Changed rubber line going to cal.
Taken off paportioning valve cleaned all ports.
Flushed out old brake fluid in master cyl.
Still have same issue.
Is there away to check or rebuild check valves in the master cyl?

TfcCDR

The check valves on some master cyls are just little rubber inserts installed where the hardlines are connected to the MC body. On others they're a plastic or metal flap or disc mounted in the piston return spring buffers (usually a nylon insert in the end of the spring). There may be other configurations, those are the two I'm familiar with, and I don't know which are in your MC.

The only reason they're in there is to keep the fluid from being drawn out of the line into the cylinder when the pedal is released, by slowing the fluid return. When you pump the pedal during bleeding, you're working the check valves to draw fluid from the reservoir and push it into the hardlines.

Back when I was young (and dinosaurs ruled the Earth), the parts places carried a master cylinder rebuild kit consisting of the cups and/or crowns, springs, check valves and boots. It's possible that NAPA has a kit for your MC, and if you look at one they can point out the check valves and tell you where to look.

I would NOT go digging into your master cylinder without a rebuild kit AND INSTRUCTIONS detailing how to do the rebuild!

It might be better just to replace the MC (and could even be cheaper than the rebuild kit). It doesn't take much to mess up a master cylinder, so it might be cheap insurance just to swap it out.

One possibility that I would check first is if the caliper piston is shot. If there is a scored or pitted bore, a gummy cup or damaged piston, it might work just fine when you apply high pressure to the system, but bind up rather than returning to "relaxed" position (it doesn't move very much).

This is easy to check -- pull the wheel, pull and clean the caliper, then have a helper VERY gently press the brake pedal (with FINGERS) while you hold the caliper piston(s) with your thumb(s). Now GENTLY use a pair of pliers to return the piston(s). If everything doesn't feel perfectly smooth, there is any binding, or one returns more easily than the other (or the other doesn't return at all), you have a piston problem.

vip3r82

I put pressure on the system and then took a wrench to each fitting working my way from the mc to the caliper each time i checked the rotor to see if it would turn, "no luck" lol the top pistion is harder to push back in. I do have another concern as well. When i first changed the brake pads on the front, the passanger side looks like they still had over 60% of there pad left. Could this be caused by the old owner not bleeding the system corectly?
Any ways as soon as i get the cash i will replace the caliper and let you know.
Thanks for all the information and help. And sorry if my spelling is bad, 6am and no sleep for 36 hours. Lol

vip3r82

This is the color of the brake fluid that came out of the original caliper.

The reasion why i changed calipers in the first place is that the guy i got the stang from i guess usex a C-clamp on each piston without using the old brake pad or a block of wood when he compressed the pistons, .in turn chipping both pistons. The black fluid i got out of the original caliper when compressing both pistons each piston compressed very smothly. The chips in the pistons are not bad at all. Pic posted soon

vip3r82

This is the chipping of the pistons on the original caliper. My question is this, could this caliper be used for a month or two untill i get my school money and or tax refund?

PNYXPRESS

So the original caliper worked fine and the new one locks up? That would point to either bad caliper or improper install.

vip3r82

Not really, old caliper top piston was dragging, and is chipped. "Improper install" that's funny since i have been doing brake jobs for over 10 years. Just never ran into this kind of issue. Even on my F150.