Help!! major brake problem....
 

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..

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

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??

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

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

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

Hmmmmmmmm just too many 3" exhausts out there under the names....lol. Again, I wouldn't try to rebuild the master cylinder. You never know if the cylinder is pitted or worn too much. The rebuilt from the parts stores are your best bet, sometimes it is a huge hassle getting that C-clip back in and if you haven't done a few, you might put a piece or two in wrong, so just to be safe.......u know.


Russ

just a suggestion, i don't know if it will solve the problem. it probably wouldn't hurt to bleed the brakes in case there's any air in the brake line that might be causing the inconsistancies in braking power.

I'd put money on it that its the master cylinder, has happened twice to me in different cars, and was not much to fix at all, the symptoms you describe are the classic master cylinder problems.

[QUOTE=rnoswal]Hmmmmmmmm just too many 3" exhausts out there under the names....lol. Again, I wouldn't try to rebuild the master cylinder. You never know if the cylinder is pitted or worn too much. The rebuilt from the parts stores are your best bet, sometimes it is a huge hassle getting that C-clip back in and if you haven't done a few, you might put a piece or two in wrong, so just to be safe.......u know.

YEA !!! I don't even have 3", its 2 1/2" ........I tried to find out how to change that to something else, like on SM, but ????

Anyway...you guys are correct in that the master cylinder is most likely the problem. But...the leak-down is 'internal'...so no external leaking.

Buy a remanufactured one, be careful not to get air in the lines. If you do, the ABS (if you have it) will F*** up and you'll have to deal with that.

I suggest that you go have it checked and replaced at a 'good' (not a ripoff one like Midas or Pepboys) shop. Let them take on the resposibility of making sure its working properly when its completed. It should not be more that 1 hours labor, and about $60 for the part. (That's all I'd charge at my shop.)

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