Help with brakes on 93 Jeep Grand Cherokee

[uphill]

I just put new brakes front and back. But I have no break pressure when you push on the break pedal. It goes to the floor the Break light comes on, on the dash. Take you foot off the break pump the pedal once and the light goes off. I can build a little pressure but not enough to drive it safely. Is there anyway to test the master cylinder? Or is there something else I should be looking at? Thanks for your help?

[Jeremy airjer W]

Did you pump up the pedal after you installed the brakes. After the pistons are pushed in and the new pads are installed there is a lot of gad between the pads and the rotors. It will take a few pumps to get the pedal back.

If it still does it after several pedal pumps than typically one of two problems is present. One being an external fluid leak (leaking line, fitting, wheel cyliner) and the other is the master cylinder failed. Quite possibly do to the fact that you pushed the pedal all the way to the floor.

If you opened the bleeder screws or opened up the hydralic side of the system you will probably need to bleed the system.

[uphill]

Yep pumped the pedal, did not open the bleeder screws the only thing I did was took off the caps where you fill the brake fluid when I pushed the calipers back in. Should I have leftthem on?

[Jeremy airjer W]

Than I would recheck the rears to make sure they are adjusted up properly. If that checks out then recheck the wheel cylinders, lines, hoses, for fluid leaks. If that check out than there is a good possibility that the master has gone bad. If you pushed it all the way to the floor than thats when it probably went bad.

Typically a master never sees its full range of travel. Debris and corrosion collect at the very end of the bore that never gets used. When you push the pedal to the floor the seals in the master travel through all that debris and corrosion and destroy themselves. I see bad masters often in older vehicles that come in with fluid leaks and blown brake hoses.

If the master is bad than I would highly recommend going new. Although there is no gaurantee that the new one will work either but the chances are much higher. Just this last week we put 3 masters in an old cadalac. The first one was reman and didn't work, the second was new and didn't work (at this point we are doubting ourselves) and the third, new, was the charm!

[uphill]

Thanks Airjer, I just talked to someone and they said the same thing. The break pedal went to the floor before I changed the breaks and I just figured that the pistons on the calipers were fully extended. So I just ordered a new master cylinder only 40 bucks.

[Jeremy airjer W]

Your welcome! Thanks for posting. Hope that fixes it!!

As long as there is fluid in the master the pistons will keep pushing out until they finally pop out of ther bores. The pedal will feel fine until this happens. of course you will hear a couple weeks worth of grinding brakes before this happens. I am lucky enough to see this at least 2-3 times a year!!