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Hi all, I'm hoping someone can provide some insight to this brake problem. I apologize for the length of this post.

My parents have a 1996 Taurus which has front and rear disc brakes. They told me it was having brake problems. When I initially looked at it, the brake pedal had excessive travel and the rear brakes had some major issues - the rotors were covered in rust, one caliper guide pin on each side was frozen to the caliper bracket, and one of the calipers was frozen solid - basically no rear brakes what so ever. We replaced the rear rotors, caliper brackets & guide pins, the pads, and one of the rear calipers.

I moved to the front of the car and removed the front calipers for inspection. The caliper pistons both seemed to move fine. The pads themselves were pretty rusty, but they had a lot of lining left and the caliper guide pins moved freely. So I wire brushed the pad contact points, put on fresh grease, and reassembled the fronts.

After doing that, the brake pedal still had excess travel. Basically it feels like it only just starts to "bite" just before it bottoms out. I thought that there might be air in the system, so we replaced all the brake fluid and bled the lines. Still the pedal traveled basically to the floor. If you're coasting at 5 mph and push the pedal to the floor, the car will gradually come to a stop. I figured the only other possible issue would be that the master cylinder is bad. So we pulled the master cylinder, bench bled and installed a re-manufactured one. Then we re-bled the lines and there is still excess pedal travel. The brakes kind of work, but the car will not do a "hard stop".

I have not seen any indications of leaking brake fluid on any of the lines or around the calipers.

If anyone has any ideas or insight about what to do next, I'd be very grateful.

Steve  

how about the rear brake caliper adjustment..

the rear disc brakes have the parking brake built in...

step on the parking brake pedal a bunch of times till the pedal only goes down about half way MAX.. then try the main brake pedal..



you can check the parking brake clearance...  remove the rear wheels. . put the lug nuts back on.. so the rotor is held tight against the hub..   see if there is ANY clearance between the pads and the rotor face...  work the parking brake lever on the caliper until the piston stays out moving almost all the clearance...

you might be able to do this with the wheel on.. i have not tried it on a taurus...

does this car have ANTILOCK brakes..???????

does the ABS light come on for bulb check when you start the engine.. for 5 seconds or so...

does the ABS light come on when trying to brake at a ANY speed..

cars with ABS can have weird problems like you describe..

i am hoping that you know.   that when you retract the calipers that you loosen the bleeder screws while you carefully depress the pistons with a clamp.. so that no air is entered into the caliper.. and NO fluid is pushed backwards up the brake lines through the antilock control module..  

Thanks for the info.

I think the first thing we will try is getting the parking brake rear caliper adjustment.  After all the work done on the rear brakes, the parking brake cable is sagging, so I figured we need to tighten it at the adjustment nut.  But we'll try stomping on the E-brake pedal a bunch of times first and see if that has any effect.

When I retracted the calipers, I didn't loosen the bleed screw, but afterwards, we bled all the brakes (several times), so I don't think there's any air in the calipers.

Steve  

figure out why the cable is sagging .. after you verify the rear calipers are in adjustment..

do not tighten the cable adjustment more than needed.. you don't want the parking brake levers to be pulled off their stops..


the springs retract the parking brake cables...  the cables should NOT pull the adjuster off away from its seated position when the parking brake is released..






 

ONE serious warning...

DO NOT USE silicone dielectric tune up grease on the caliper slides..  it will cause the caliper pins or slides to seize like they were welded..

use brake caliper slide lube..   white lithium grease.. silglide..


dielectric tune up grease is for thermal transfer of heat from electronic components .. so they don't overheat and fail..
it contains dissolved silica sand  ..  get it hot enough and the dissolved materials become sand again.. paste to a solid..  not a good thing to have in something that has to slide with NO friction..  

Ok, here's another question then about the rear brakes.  When I pulled the rear calipers off, to initially retract the piston, one side the piston was completely frozen and we replaced the caliper.  The other side, the piston was tight, but I was able to get it to fully retract (using the special tool that simultaneously rotates and compresses the piston).  Do you think that this tight caliper piston could be causing the problems?  I would think that a tight caliper piston would cause weak braking on only that one wheel, but wouldn't effect brake pedal travel, or the braking on the other three wheels.

Steve  

does it have ABS brakes....

the ABS system could do exactly that.????

I thought that there might be air in the system, so we replaced all the brake fluid and bled the lines. Still the pedal traveled basically to the floor. If you're coasting at 5 mph and push the pedal to the floor, the car will gradually come to a stop. I figured the only other possible issue would be that the master cylinder is bad. So we pulled the master cylinder, bench bled and installed a re-manufactured one. Then we re-bled the lines and there is still excess pedal travel. The brakes kind of work, but the car will not do a "hard stop".

does it still do this...

describe your exact problem again.. as currently after checking the rear calipers..

does the parking brake hold????   will it only go down a few clicks...????

does the brake pedal go to the floor???   does it go to the floor with the ignition key off????

what happens if you pull the ABS fuse??  

I'm almost positive the car has ABS brakes (has the ABS light on the dash, although I don't know where the ABS module would be located to confirm this).

I have not had the opportunity to check the rear calipers.  Unfortunately this is my parent's car and it's located 70 miles from my home, so I can only work on it occasionally.  

The parking brake pedal has excess travel, the same as the main brakes.  You push the parking brake all the way down to the floor and the brakes will bite, but not hard, so I think the parking brakes need adjustment (also, as I said, the cable sags when it's released).  I'm going to tell my dad to pump the parking brake pedal a bunch of times as you described to see if that helps.

I believe with the ignition key off, the main brake pedal will pump up and get firm.

I didn't try pulling the ABS fuse.  Sounds like it's something easy to try.  What do you think the effect would be?

Thanks for all the feedback.

Steve