changed master cylinder and still weak brakes???

[stanlam]

I have a 1992 Ford Explorer with over 200,000 miles. The car is stock with 2 wheel ABS brakes. The problem is the brakes are really weak. The brakes were inspected by a mechanic and everything looked fine. Then the mechanic tried to bleed the brakes. The front brakes bleeded fine, but the back brakes didn't bleed at all. From there the master cylinder was replaced with a new one. After replacing the master cylinder, the back brakes would bleed better, but still very slow. The brakes was tested again and the brakes are still weak. Any suggestions? Is there something about the 2 wheel ABS that is making this job confusing?

 

[Dlee6204]

There is a Rear ABS Module/Valve that can often get crudded up and cause problems with bleeding the rear brakes. They can sometimes be taken out and cleaned up but it might just need to be replaced. It's located in the frame rail on the driver's side.

 

[kona_mtb]

I had this problem with the front brakes. Changed the master cylinder and still weak, dealer said everything looked fine but that he could change my pads, rotors and calipers just to see. Wanted $1200 told him to screw himself and changed my brake hoses. Fixed the problem

 

[bats]

Check your brake hoses for leaks. Rub them down with a mixture of soapy water and have some one pump them while some one checks the lines for leaks. Another thing to look for is a vacuum leak. Two of my vac lines came off and I had ridiculously weak breaks.

 

[stanlam]

Thanks guys for the help. I also got somebody who mention this thread. does it sound correct????

http://www.explorerforum.com/forums/showthread.php?t=60093

There is a bleeder valve on the RABS module, now this is a RABS module and not a ABS module correct? It mounts on the drivers side frame about 18" in front of the rear axle, correct?

Bleed this sucker first, then bleed the rear brakes as you normally would. You can see how it sits on the frame that the bleeder valve is up high right where the air bubble will rise too. Failure to do this will result in a soft pedal and pulsing/grabbing rear brakes..also a possilbe RABS light.

 

[YBCold]

ive made a write up about replaceing the RABS valve. sometimes they just rust from the inside out or get air trapped inside and need be sequenced. some OBD scanners can sequence them for you.

heres some threads i participated in. might help. wouldnt hurt to check all your lines

http://www.explorerforum.com/forums//showthread.php?t=257833

http://www.explorerforum.com/forums//showthread.php?t=261342

 

[92exp4x4]

I took mine out, left the connector plugged in, zip tied it to the frame and plumbed new brake line around it.

No more problems.

 

[stanlam]

Thanks for all your help everybody. The car is finally fix because of this thread....

http://www.explorerforum.com/forums/showthread.php?p=2626293#post2626293

Basically I went to the auto store and spent $5.00 on a 1/4" union and did a bypass of the Rear ABS. That was super easy. I don't really care for the ABS since my car is 19 years old.

 

[de]

RABS valve

ive made a write up about replaceing the RABS valve. sometimes they just rust from the inside out or get air trapped inside and need be sequenced. some OBD scanners can sequence them for you.

heres some threads i participated in. might help. wouldnt hurt to check all your lines

http://www.explorerforum.com/forums//showthread.php?t=257833

http://www.explorerforum.com/forums//showthread.php?t=261342

Hi. I will try it this week but my Ford shop manual page 06-09-46 of the Anti Lock Control, removal and installation of the RABS module, after installation, instruction #4. Bleed the brake system as described in Section 06-00 Brake - Hydraulic-General service. It is not necessary to energize the valve electrically to bleed the rear brakes.

The Haynes manual says that one should take the car into the shop.

So hopefully I'll be able to bleed my master cylinder as described in both the shop manual and the Haynes manual then bleed the brakes at the wheel cylinders w/o any complications. Now cars with full ABS and a HCU, that might be a different story.