Hmmm....weird. Check the connection between the brake pedal and the master fluid? Maybe its before the pressure hits the brakes. But you can pump them? So its not like the brake pedal gets stuck?

And they lock up...I'm guessing no ABS?

I'm out of ideas.

 

Its so crazy....I really want to burn the car.

This is the FIFTH time this has happened within the past month.

1. First time Proportioning Valve was taken out cleaned along with the master cyl then all 4 bleed.
2. Locked back up within 70 miles. Proportioning valve then replaced with a different one. All 4 lines bleed
3. Car was great for approximately 70 miles so then we switched out the ABS unit. Car was great for 1000 miles. Even ran it hard at the track. Bill said it was dragging then, I just forget what NORMAL breaks fell like in a supra.
4.Then got the SS lines for all 4, was great for maybe 100 miles
5.Now it sits again with the same problem.

This car must hate the 1jz and is just demanding we put a 7m back in it. I have no clue. We are open for ANY suggestions because there isn’t much left and the possibility of both calipers locking up consistently at the same time all 5 times is completely crazy.

 

its got to be the calipers. the rubber seals in the calipers are old and get hot and lock up. i'd say its time for a new master cylinder and new calipers. my brothers 85 celica does the same thing and he has steel braded lines on it already, so we started replacing calipers. but the therory of the car rejecting the 1j is a good one. heheheheheehhe or maybe the car is afraid of going really fast, your lucky, my mk3 loved going fast, but didn't like to stop.

 

Well , I dont know what to say other than if you let chris take the car up here I can look at it , this really sucks i know but dont even think about burning the car it is too mint.

 

Your problem sounds like a fluid return issue. When the brakes begin to heat up, the brake fluid expands. The excess fluid must return back to the master cylinder reservoir through its compensating ports. If the fluid can't return, it forces the caliper pistons out locking up the brakes. If the master is adjusted wrong, the master pistons cover up the ports preventing fluid return. I would also check for any pinched or kinked hard lines. Just some thoughts.

 

yea, i inspected the hard lines way back when... when i rebuilt and inspected the master cylinder. the operation and components inside the master cylinder are in like-new condition and moved smoothly. all the seals were intact and the bore was not blemished. the proportioning valve was full of Crap, dirt, burnt fluid and sediment. the spring and valves inside were actually siezed and stuck together by the crud.

i just pulled the calipers off and checked the operation of the slider pins. the upper pins had minimal lube on them. the lower sliders moved smoothly though. i cleaned the upper pin off and used some axle grease. took it down the street and back. stomped on the brakes, locked them up a few times to cycle the ABS... no hitches yet.

one thing i need to find are the anti-rattle clips for the pads. the right side (problematic side) is missing both upper and lower clips. the driver side is only missing one clip. im not talking about the ones that sit in the caliper bracket, but the V-shaped spring-clips that apply outward pressure on the pads themselves.

anyone know where i can get them clips?

 

If you can post a picture of what you are looking for, I can look for them at a local junkyard. They always seem to have at least 2 Mk3s (hell I want to kill myself for not being able to buy a pristine one that only had no battery) there, and rarely dont have all the parts. Dunno the condition they'd be in, as mostly they are just 'average', but at least I can get the parts for cheap, regardless of price. I'm not looking to profit from this if I could do it, however I'm not sure when I'd be able to get them to you.

 

i wasn't talking about the caliper sliders, i was talking abou the rubber seal in the actual caliper on the piston, they wear out and get old just like everything else, thats why i said it could be the calipers. when the piston moves back and forth in the caliper there is a rubber seal to keep teh brake fluid from getting past the piston and shooting out onto the pads. you would have to take the piston out of the caliper to see the seal i'm talking about. it would be easier to just replace the calipers with new ones. if there is dirt and grime built up on that seal it would cause the calipers to lock up some times.

 

oh bill those are new calipers since the 1j has been in the car. They are remanufactured and I had a friend powder coat them and I did notice a little powder coat on this rubber seal you are talking about. Could this cause the problem?

on and the tiny brackets flubyux2 is talking about is a small v looking dealy that keeps the pads together or something. I'm not exactly sure of its function. What junk yard did you see some mkiii's at? I need a few miscellaneous parts.

 

they are the anti-rattle clips... not to be mistaken for the anti-squeal shims that you are supposed to glue to the back of the pads. these clips are V-shaped, thinner in diameter than a coat hanger and the tips of the V go into the metal backing plates of the pads themselves. they apply outward pressure on the pads, away from the rotor surface.

the rubber seals you see on the calipers themselves are actually just dust boots... they dont actually hold in the brake fluid or any pressure. there is another rubber seal on the piston, like a piston ring, which seals the piston against the caliper body. if youve ever taken apart a master cylinder or slave cylinder, you know what seal i mean.

i may be able to adjust the brake pedal actuator rod so there is a little slack. i suppose its possible that the pedal rod is overadjusted and applying a slight amount of force on the master cylinder itself and the pistons in the master cylinder are unable to retract and return to their at-rest position. ill try to mess with that tomorrow. if youve ever adjusted the clutch slave cylinder rod under the dash on a car, youll know which rod i mean.

but, these brake lines are bad ass. you can feel the brakes grab as soon as you apply a tiny bit of pressure, and its like stepping on a board... which is how it should be. im so used to pedal travel equating in to braking force. in reality, brake fluid doesnt compress and in an ideal situation, the brake pedal would NOT move at all, except to take up any slack in the physical portion of the braking system (clearance between pads/piston and rotor, clearance between brake pedal and master cylinder) then it would come to a stop and the pedal would no longer move. at this point, brake pedal pressure equates into caliper pressure and braking force. this is EXACTLY what these brake lines do. the harder you press the pedal, the harder the brakes grab; as it should be... WITHOUT brake pedal travel.

i would highly recommend these brake lines to anyone who uses the brakes on their cars!