Help!! major brake problem....

[bigal0043]

alright so i was driving home last night from school and the brakes went completely soft.. like went to the floor... but i could pump them to get pressure... after i got it pumped to stiff again i held it in to see if i was losing pressure but wasnt... it only seems to loose pressure when i dont use it and after like 15 mins of driving.. it is fine before everything seems to get warmed up...

but it happened again when i was in the city but on the way to work... on the highway getting off the exit..

and once it lost pressure u have to pump it for the rest of the time in the car till the car cools down... any ideas?? i was thinking an air pocket maybe???

the brake pads are pretty thick so its not that and it is not losing brake fluid it is completely full..

[rnoswal]

Well that usually means the brake master cylinder is bad. The piston inside has seals and the seals are letting the fluid go by and then no pressure. It could actually be leaking into the brake booster and that is why you don't see any fluid on the outside. If you pump them up for now, it will hold, but this won't last all that long. Another symptom is after you pump it up is putting slight pressure on the brake and see if it slowly goes to the floor, just another sign of master brake failure.


Let us know how it goes.

Russ

[bigal0043]

i hope it is just a break in a line somewhere then.. but it is weird that it just started to happen out of no where...


how much is a new master cylinder... think it would be cheaper to find someone who has a used one.... can i rebuild one??

[joel w]

remanufactured is about $40 +- and new is about 120+-
they make rebuild kits but i would not recomend them. atleast with a remanifactures the liability is on them if it fails. brakes are important!!!, I would not want to risk mine and other peoples lives to save a few bucks? Just my opinion..

. here is a pretty good online auto dealer, ive used them many times. and there competitive in price to the local guys

http://www.rockauto.com/catalog/cata...&parttype=1836

[rnoswal]

If it was a broken line then the pedal wouldn't go to the floor because, depending on if it is the front or rear that is gone then the other will still work. Safety feature. Go to the parts store and buy one from them. They are fine and have a warranty. If you want to check to make sure there are no broken lines, just pour in some fluid and put it on dry pavement, step on the brakes a few times and if it is leaking you will see a wet spot on the ground. If it is the master cylinder, sometimes if you look under it, on the brake booster you will see a trail of wetness and bubbled up paint.

Russ

[SupraMan1784]

i think the master cylinder is shot...rnoswal said it right...the seals are shot too thats why its goin soft, pump it enough times and it will create a seal on its own..which is why the pedal got stiff again, rebuilding the master cylinder should fix the problem....but also check the lines...might have a small leak, or some air in teh lines

[GCPRO]

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?

[Isphius]

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