when i meany rebuild i dint mean take it apart and put it back together..i meant get some new parts from either a dealer that deals with brakes or ones that are refurbished to work as good or better than the factory and nickeleye is right...the leaks will be internal not external so if it is the mc there is no need to check for a leak under the car unless u really messed it up

what i found weird was if it had a internal leak wouldnt it be draining out some of the brake fluid out of the resevoir? because mine is still topped off hasnt dropped any at all...

Well yeah, that was mentioned by someone earlier. The seals get soft and allows the fluid to blow by the seal on the piston inside the master cylinder. You can tell a lot of the times by just putting light pressure on the brake pedal and you can feel it go right to the floor. This doesn't always work, but many times that is one way to tell that it is an internal leak, or blow by. Usually you get some minor leakage into the brake booster.


Just go buy a brake master cylinder at Advanced auto or another parts store and put it on. Make sure you bleed the master cylinder first then the wheel cylinders. It wouldn't be a bad idea to make sure the fluid comes out clean on all the wheel cylinders so you have fresh fluid in the system.

Keep us informed.

Russ

k thanks for all the help guys... i havent had time to do anything yet... tomorrow is the day i am installing everything....

boost gauge and pillar pod... turbo timer
fix my turbo pressure... now that is is getting cold out i cant push it hard without hitting fuel cut

and well now check these brakes out... im excited about tomorrow now... going to be lots of fun...

Alright ill update everyone... there was an option for an wideband on my turbo elbow and it fell out... must not have been tight... but anyway that was blowing the exhaust air right on my brake lines causing it to boil my brake fluid... So my problem is fixed now...

my brakes had symptoms like that when i first got it, but it was low on fluid. and it has done it randomly about twice since then, lose tiny ammount of pedal pressure than it comes back. a friend told me that is exactly what happened to his car and he replaced the master cylinder and it was fine...so im guessing that is a good assumption. and yah what is with the 3" exhaust...i was also trying to change that. haha.

I agree with most of the others, seems like the master cylinder. I had the exact same problem with my clutch slave cylinder. Piston seals were shot, fluid was shooting past it and not letting me generate any pressure unless I pumped the clutch. Also explained my loss of fluid...

Replaced the cylinder, problem solved.

Soft fading brakes - tried usual stuff
 

My '90 Supra with ABS has had a soft braking problem for over one year.

So far, I have:
* replaced the master cylindar twice with rebuilts - no difference
* replaced all calipers with rebuilts
* replaced/bled all lines (in the prescribed order)

Symptoms remain: soft pedal reaching almost to floor with limp braking, with an evental more dramatic "grab" as the car slows down.

I am at a loss as to what to do next. A couple of observations that I don't know how to interpret:

When bleeding the lines after caliper replacement, I do a "no backpressure" bleed until the fluid shows no air. Then I have my assistant hold the brake down too build up pressure at which time I open the bleeder. I noticed that sometimes the fluid sprays out forcibly and other times it dribbles - although there is no evidence that air is in the lines.

Assistant reports pedal still travels close to floor even though new calipers have been installed and air is removed from the line.

Questions:
Are there any other components of the brake system that could impeed/limit fluid pressure to the calipers other than the master cylinder? Are there solenoids or boosters or orifices related to the ABS that I should look at?

Any other suggestions?
is there any other part of the system that I should look at?
how about adjustment of the piston in the master cylinder. Is that something that might be fruitful?

get new rotors. And pads. It sounds like rootrs are too far worn. And check the actual connection between the pedal and the master cylinder. And also if it has a pedal heigh adjusment? im not sure, But if it does check that