I drive a 1994 4 cylinder automatic geo tracker with only 61,000 miles on it. in feb. of this year is sitting,

Question

in traffic, as the traffic moved up, i moved up but when i applied the brakes the car would not stop, i had to throw the car into park, to get it to stop, after doing so the wheels spun like crazy. i was able to drive the car home and it never happen again. i checked the brake fluid level and it was okay, i checked for leaks there were none, thing it was just a fluke,( i had new brakes put on in 2005) i contiue to drive and the brakes worked perfectly, until this weekend, it happen again, only this time when i applied the brakes, the car accelarated
so fast i could not throw it in park. i hit the person in front, neither one of us was hurt luckily, and there was no damage to either car, our bumpers matched. i did have to be towed, because i was blocking traffic. when i got my car home again (and there it will stay) i checked the brack fluid was not low, and i found no leaks,*are there any auto mechanics out there with suggestions?..especially from Virginia Beach,Va, or anywhere...HELP

Answer 1

Is the pedel going all the way to the floor, or are you maintianing constant pedel pressure and getting a firm pedel and just nothing happening with the brakes?

I will check back to help answer.

Since there has been no responce, I'll just give out a few pointers. If the master cylinder has an internal leak, I've seen them where on usual braking, the pedel is firm and hard, but in a panic stop (hard braking) the pedel goes to the floor, this is caused by seals on the inside of the master cylinder pisons(eiter primary or secondary piston) do not contain the fluid its susposed to because the seals are weak or damaged. It will occure on hard braking and not on soft because on hard braking there is more force being applyed in a shorter amount of time and the seals will buckle or seperate under the force. However on standard braking (soft braking) the seals will hold up under the same pressure, but will stay together because the force being applyed is different. The seals will tend to hold together more if thier being gentally eased into pressure, instead of being forced to opperate in thier fassion.

If you are getting a firm pedel and the pedel feels nothing out of the ordaniry, this could be casued by brake fade. This is caused when extreme heat "treats" the surfases and creates a "mirror" affect. This mirror finish and exetreme heat will cause less friction, this reduced friction will make braking harder. Its like taking a 10lb weight, and pushing it with 10lb of force on a concrete surface and taking the same weight and pushing force and sliding it on an ice covered surface. The concrete surface will represent brakes working at thier full potential. The friction on the weight's and the concrete's curface's will cause the weight to slow down quite quickly, this is how brakes are susposed to work, a good amount of friction, the better it will be for stopping. However, using the same wight and the same force and haveing the weight slide to a stop on the ice will take a lot longer because the friction of the ice is less then the friction of the concrete, this will cause the weight to slide longer before coming to a stop. This represents brakes when they are "mirrored". \

Brake fade usually indicates that the brakes have been heated to a point of being so hot that they have changed the properties of the metal(s) in the rotor. Brake fade can be cuased by worn or thinned rotors, or by high speed stopping. Anything that can cause excess heat or reduced heat dicipation can cause brake fade. Usually, the rotor(s) have to be replaced and same witht he pads (and at times the calipers as well) or other mating surfaces.

There are a few posibilties, I would suggest, before starting to rip everything apart and replacing parts at random, I would take it to a brake shop and have them diagnose the problem. Not all brake parts are cheap, and this problem may be caused by other things. The two that I have listed are just off the top of my head, I'm not limiting just to that, but to be sure, a full diagnosis will be needed. Have it towed to a brake shop and tell them the problem, and what the conditions that problem have occured were. They will be able to diagnose the problem (using existing information, and conformation), or by process of eleimation. I have seen some booster and master cylinders reach into the high hundreds ($800+/-) in some cases. Sometimes paying $50-$100 diagnosis is better then "shotgunning"*(1) a problem. It may save you a lot in the long run, and you know that the problem is being solved by a trained individual. Brakes are something that should not be taken lightly, they are the most inportant part of your vehicle.

*(1) Shotgunning - throwing parts at a problem in hopes that it will fix said problem. This is usually done if diagnosis has not been done, or if no diagnosis is being done, and the most likly cause is "fixed". It may fix the problem, but it may not fix it. Proper Diagnosis is the only way to go.

Answer 2

First off EXPERIENCE!, If you don't have that, get a metric tool set, sockets, wrenches, screwdrivers, etc. Or a friend with mechanical experience. This is not a job for the unskilled. Best advice, Take it in, at least there are guarantees, and skilled people. And no don't go the shade tree mechanic route, that costs twice as much in the errors made in doing the job. If you don't follow this, then get a book for the car, read, learn, then have a day to do it, and get greasy like the rest of us who can't afford a mechanic.

Answer 3

Are you positive you are applying the brake and not flooring the accelerator pedal? I have seen that happen too many times. You think you hit the brake but actually just floored the gas pedal.

Answer 4

if it has a power brake booster I would replace that. If it doesn't have power brakes your looking at a new master cylinder.