Pulsing brake pedal

[Chic N Stew]

This is gonna sound kinda stupid, but have you checked the pads, they may be cracked or chipped or something like that

 

[metalmacguyver]

I don't believe that the problem is warped rotors. The problem only happens (to me) just as I am coming to a stop - barely moving. There is no other time it happens. Then the pedal drops/pulses and there is also a noise (hard to describe) that is comming from the pedal area (maybe behind the firewall). Kinda sounds like a very quick series of clicks. I thought master cylinder but there is no leakage.
Any additional info / help is appreciated.

that clicking sound is the ABS activating.

 

[gsxrken]

Sounds like an ABS issue to me to.
Or atleast take it for a short test drive with the ABS relays PULLED fron the power distribution box

AD- would you know where the appropriate relays are on a 99 4x4 4WABS? Thanks

 

[rparker]

more info

Not sure if it is applicable but: had to go into 4wd and the ABS light came on. Stayed on after I took it out. Did not come back on after shutting down and starting again. Also after I took it out of 4wd, was going down a slight hill, snow covered so going slow, put the brakes on and rears locked.
The real puzzler is that the pulse does not happen every time. It happens most of the time so now I am looking for it and when it does not happen it startles me.
Do I admit defeat an go to a dealer?

 

[metalmacguyver]

AFAIK, the 4wd part should not affect the abs. i would recommend having a dealer check it out.

 

[Yellowsplash]

I had the same problem. Its actually quite common. The abs sensor isnt getting a good reading on wheel speed and when you slow down to under 10 mph the abs kicks in. Seems to do it more often with only slight pressure on the pedal, and less often under hard braking. Either way, the sensor (which I believe is magnetic) is dirty and not getting an accurate reading from the rotor ring. Just remove the rotors and clean the sensor on each side with some brake parts cleaner and wipe it off real good. Should clear up your problem...

 

[shadetree]

The problem only happens (to me) just as I am coming to a stop - barely moving. There is no other time it happens.

This is one symptom of a warped rotor. As the vehicle slows, the pulsation begins, then slowly dissipates as the vehicle comes to a stop, not saying you don't have other problems, just that this is one symptom. shady

 

[bigredneck61088]

i have this same prob on my 2001 2wd and its not warped rotors, anyone come up with a solution???

 

[MAKG]

This is one symptom of a warped rotor. As the vehicle slows, the pulsation begins, then slowly dissipates as the vehicle comes to a stop, not saying you don't have other problems, just that this is one symptom. shady

And runout is very easy to measure, so it should be done before going after the ABS system. While you're at it, mic the rotors, since thin rotors can cause warpage when hot, that goes away when cool.

Though pulling the ABS fuse is a good idea.

No one asked what the conditions were. If this is on slippery surfaces, the behavior described might be normal.

 

[Joshs93four-oh]

He says that just before drawing to a stop that the pedal pulses and the pedal drops. The ABS pump is activating. I have had this problem many times with customer cars and they have all been Fords. Is the abs lamp iluminated? If not, maybe one of the speed sensors has an intermittent output but the duration of the fault is not long enough to set a code? Maybe one of the front hub assemblies is starting to go bad and there is metal particles/comtamination on one of the tone rings internally? Another possibility is that the hub assembly housing is corroded and scaled enough that the speed sensor mount surface is actually "raised up" and away from the tone ring engough to affect the air gap. If it is a rapid pulse then there is no way that it is a warped rotor because the vehicle is not traveling fast enough to create that frequency of pulses. An abs pulsation feels like the brake pedal playing a "bass note" through your foot. Josh
________
Harley-davidson model jd

 

[fastmaxx400]

I had this problem with my ranger when I first bought it. I replaced the rear sensor, and it still did the same thing. If I pulled the abs fuse it would not do it. I took off the front wheels to look at the sensor and everything looked fine so I took it to get the codes read. They told me left wheel sensor. Replaced that and still had the problem. Ended up saying what the heck and replacing the other sensor on the right wheel and it fixed it. I was about to pull out my hair. Later talking to a tech, he said that the sensors were not reading the same causing the computer to think at low speed one of the wheels was locked up. I am so glad its fixed

Kevin

 

[4.6StangRage]

mine does the same thing i checked my pads and they are thin and need to be replaced.

 

[gbadgley]

That is a very common problem with the Ranger/Explorer. I can tell you right now it is in all likelyhood in the ABS. I put 4 new rotors on my explorer and cleaned the sensors, No difference, It's just one of those things that I will have to dig into to find the real problem.

 

[yuzr]

your'e right, lost speedometer

disable the ABS... lose your speedometer and odometer

2000 2.5L auto. 22k miles, a few every day.
Drove 10 miles, 2 hours later returned to truck and found:
- ABS light
- inactive (spee)(o)dometers
- NO UPSHIFTING (so, I drive in 2nd, not revving).
Those three symptoms, no others. Invariable and permanent.
Fuse 14 visibly intact. Fluid fine.

What is your take on this interrelationship of ABS and shifting?

 

[westonoto]

AFAIK, the 4wd part should not affect the abs. i would recommend having a dealer check it out.

4wd does have some effect on abs. I don't know the mechanism of action, but when driving on ice or packed icy snow, having the vehicle in 4wd seems to greatly lessen the tendency to activate ABS. Thank God it does. The ABS is dangerous on those road conditions in my truck. No front braking power at all. Far better with 4wd on.