Brakes grab at the very end of slow stop? (1 Viewer)

[Saracal]

Just finished up a front axle rebuild and took the oppty to replace the pads on the brakes. When I went for a test drive the ABS light was on and off for a while, and the brakes seemd to "grab" right before coming to a final stop (smooth up until that point) . So I pulled the sensors and wiped them clean (there was plenty of grease on them from having repacked the birfs and knuckle) and put them back. Now the ABS light is gone so I hopefully have avoided any issues here, but I stil get that final "grab" at the end of slow brake at the final stop. Any ideas why this is happening? Never had this before so I must have done something in replacing pads and removing calipers to cause?

Thanks for the review.....

p.s. Never disconnect the calipers so I wouldn't have to bleed the brakes. Not sure if my issue is related to air in the line though?

 

[97FZJ80]

is it a jolting grab at the end or what...i guess more info on the type of grab?

 

[Saracal]

It doesn't really "pull" to one side or the other....it's almost like something "sticks" to the rotor at the very end when your speed is down and your are 10-15ft away from a complete stop.
You depress the brake pedal real slow and try to do the smoothest stop, and right before you do it's like someone/something just "grabs the rotor(s) tight and you feel the pedal get sucked away from your foot for that split second...then it releases. No noise from the brakes.

 

[97FZJ80]

theyre bled well and full on fluid right...pistons arent sticking right

 

[Saracal]

As I said earlier, I did not disconnect the calipers so I did not think I would have to bleed the brakes.....the fluid is full. How do you know if the pistons are sticking vs. some other issue? I'm not sure I can answer you correctly on this. Thanks...

 

[Jack G. Nichols]

Hopefully you pulled the ABS sensors before you pulled the axles for your rebuild. They are often damaged that way.

Pull the ABS fuse under the hood and see if that fixes the problem. If it does, replace the fuse and inspect the integrity of your ABS harness. I found I had smashed mine where it runs along the radius arm (?). I hate mud, and do not like rocks much either.

Look carefully at the sensors themselves. It is difficult to see hairline cracks in the black plastic - original ones looked like they were in an aluminum can, black plastic on the replacements I put in.

I ran around several months without the fuse installed before I finally convinced myself that I had to spend about $200 to buy the harness and sensor assembly - not available separately. I would not drive forever without the fuse, because of insurance liability if you have a wreck and hurt someone.

Cdan can get them for you at a better price.

If pulling the fuse does not help, maybe someone else can steer you into a fix.

 

[Saracal]

Thanks Jack...I will give that a shot. Is that a symptom of an ABS not working...the "grabbing" of the rotor at very slow spped right before a final stop? I did inspect the ABS sensors and they looked good, and I don't get any ABS lights coming on anymore since cleaning the grease off the tips of the sensors. But, pulling the fuse seems to be an easy trial fix so I will give this a shot. This is the #12 fuse (60A) in the realy block No.2 correct?

 

[Tyler93]

It still sounds like an ABS problem. Pulling the sensors and cleaning one more time...

 

[Squash]

If one sensor fails the ABS system should shut down...therefore my prediction is a stuck caliper.

Jack her up, have someone step on the brakes while you manhandle a wheel....drive it and feel for a heated hub or carefully touch the rotors, the burning hot one is your problem.

 

[Saracal]

It would appear as if Jack was right. I pulled the fuse for the ABS system and took it for a test drive. No more "grabbing" at the end of a slow stop. Now, I am not sure if the ABS Sensors are "damaged" or just not working correctly due to too much grease around them? Before I pulled the fuse, the ABS light was not coming on (or at least not after I cleaned them off) so I don't know if that equates to sensors working O.K. I would guess not since without ABS working I no longer have the grab?! Engine light does not come on constatntly either. Is there any way to further isolate this issue down to an ABS Sensor without too much trouble. Thanks all.

 

[Saracal]

Jack, When looking at the sensors now that it appears as if this is the culprit, what am I looking for? I cannot remember seeing any physical blemishes and/or cracks in them and honeslty, when wiped they looked brand spanking new. They are metal and not black plastic. I did leave one in when I removed the axle/birf (albeit very carefully); would just a slight bump damage this sensor? In otherwords, would I have to "see" physical damage to one to assume I did irrepairable damage? It looked like from ther FSM that one could test these sensors via continuity/resistance?
Thanks,

 

[Jack G. Nichols]

Sorry, I cannot answer your question directly.

My original sensors were the aluminum body/color, and looked fine when I pulled them too. I gave up and replaced the sensors and harness (come only as a set) and during the installation of the new set discovered my harness had been smashed. That was ten years and three moves ago, so the originals are history. I could detect no damage on the aluminum sensors either, but my issue may have been only the damaged harness wire. As a better diagnostic I might have tried to fix the damaged harness, but it did not turn out that way.

The sensors/harness assembly is apparently carefully balanced, and I am not sure a simple ohm continuity reading would be adequate. In any case, I did not try it. If is was that simple a single sensor replacement might work, and not require a balanced assembly. Pure conjecture on my part and a moot point.

I have heard others that use the black plastic (like my replacement) housing sensors have discovered thin cracks in the body, maybe caused by removing the axle without removing the sensors. The space between the reluctor ring on the axle and the sensor is very small, apparently not affected by grease on them. I suppose manufacturing defects in the sensor housing could cause cracking, but would be surprised to find a defect on a new Toyota part.

I just turned 231,000 on mine, all but 70,000 (or so) on the replacement sensors, and have had no other problems.

Hope yours is that easy. Good luck with that.

 

[Grench]

... discovered my harness had been smashed.

Do you recall where the harness was smashed in relation to the vehicle?

My ABS has recently started to exhibit funky behavior. It does not do it every time, but a couple of times is enough for me to start looking for where the issue is.

Gentle braking, get under about 3-5 mph and the ABS engages (I can feel the dadadadadada in the brake pedal. After about 3-5 times of doing that on any given trip, the ABS light comes on and the issue stops.

The next time the vehicle starts, it apparently resets and I may or may not get a repeat performance from it.

The axles were last opened up 14 months ago at SleeOffRoad in the course of getting re-geared. So, if the sensors have issues, it wasn't from and axle service oops.

So, do you happen to recall about where in the wiring harness I should be checking to see if it got smashed?

Thanks!

 

[Jack G. Nichols]

ABS Harness

On my 93 the harness runs from the right front wheel, across the axle to the left side, then makes its way back along the left radius arm. Mine was pinched right on the bottom of the arm, and I considered welding a half pipe of black iron for it to run in, but have not done it. Get on a red neck creeper (cardboard box) and slide around under there, not hard to find.

I think if you have an intermittent problem that checking for pinched wires and loose connectors would be a first step. I would pull all the connectors and fill them with silicone grease, then reconnect. You might find a corroded pin in a connector, or something like that. Might run a continuity test from the wheel sensor to the plug back by the driver foot well.

If you have a pinched harness wire you might try to repair it - if that does not fix it, Cdan can get you a new one, $200 or so, includes front wheel sensors and matching harness.

Please report back what you find.