99 4R Braking problem: pedal goes to floor

[djhyatus]

There is braking, but very minimal. While it's running, you can almost get the pedal to maintain normal pedal height if you can rapidly depress the pedal fast enough. While it's OFF, you can build pressure and maintain a hard pedal. When being driven, the braking feels as if only either just the front brakes are being applied or just the rears. The master cylinder res. is maintaining it level, there is no fluid leaks that i can see (i.e. took both front and rear tires off and physically looked at all the lines and cylinders/calipers going from MC to all 4 tires). I just got done replacing the MC and it still hasn't fixed the problem. I'm starting to think it might be the proportioning valve for the front brakes.....

Any suggestions??? Please help...

Thanks much,

Hyatus

[Greasygreg]

was there a problem with the origional master cylender or did you change it to correct the braking problem?did you then bleed the brakes, verifying that fluid was coming out of all 4 wheel clyenders?

[djhyatus]

Yes.... I did bench bleed the master cylinder before i installed it and i did bleed the brakes starting from the farthest wheel and working my way toward the closest wheel. Turns out the MC was not malfunctioning, i thought it was, thats why i replaced it. Too bad special order parts can't be returned...

I'm at a total loss as to what could be the problem

Any help is much appreciated,

Hyatus

[Greasygreg]

well, Hyatus; it sounds like you followed the proper procedures, in changing out your mc, so i think you've eleminated that as the source of the problem,maybe we need a little more background info here...I had a buddy with a 97(abs) who put in a 4"lift,and his rear brakes stopped working.turns out he didnt install some bracket that relocates the rear proportioning arm,(bolts to rear diff housing,)and it messed his brakes all up.So now im gonna ask,does your truck have abs? has it been lifted?did your problem come on all at once or has your brake petal travel been an issue for awhile? Im trying to narrow it down with any information, as there arent too many parts in the brake system

[djhyatus]

This 4R does not have ABS - No modifications were made to the vehicle at all (wifes vehicle ) - And yes, the problems onset was immediate.

I've spoken with a few people i know who've worked with brakes before and their stumped as well. None of them have ever worked on a proportioning valve, so any symptoms arising from that component would be overlooked. I've never worked with one either, so i would not be able to tell if that was the problem for sure. I've read up a little about how one works and i think it would be a possibility. Either that, or the check valve located directly under the MC. Since both of them are dealer parts and today just happens to be a sunday, i guess i'm @#$% out of luck trying to replace those parts .

Any other suggestions?

Help is much appreciated,

Hyatus

[djhyatus]

Here's a link that comes close to explaining what my symptoms are: http://www.aa1car.com/library/2004/ic30444.htm

The Load Sensing Proportioning Valve is the type out 4R's have.

[joebruva25]

Have you done a brake job recently?, cause i did a brake job on a corola and had the same problem i did the master and the proportioning valve and it did'nt help 1 bit so i took the pads out and had a friend push the pedal very gently, the piston in the calipers moved only a bit so we continued this until they almost came out of the calipers(be very carefull not to blow them out) then i compressed them back in being carefull not to lodge them into the calpiers wrong, needless to say this corrected the problem. hope this helps!