Hi All. I have been having trouble with the brakes on my '03 4wd 150 for a couple weeks and Ford can't seem to figure out what is wrong. When I step on the pedal at slow speeds the pedal pulses drops towards the floor then grabs again. Occasionally as this is happoning the truck pulls to the left quite hard. No lights or codes are showing up. I have replaced the front rotors and pads, as well as the front left caliper and ABS sensor. None of these repairs have reduced the problem.
Any Ideas?? Thanks for your help.

 

Sounds like some sort of ABS issue... you say the pedal pulses.

You also say it pulls to the left... that would indicate that you are getting ABS action on the right side of the vehicle, not the left. The ABS reduces the pressure on the right side but the left side still has full pressure and that is what pulls the truck to the left.

It could be your ABS speed sensor on the right wheel. Or it could be the control module. I would try the speed sensor first.

Is it a continuous problem? You could also try removing the fuse for the ABS to verify that it stops the problem. This would confirm that its somewhere in the ABS.

 

Thanks for your response, the problem only occurs at slow stopping speeds. I removed the fuse today and drove around a bit. This seemed to stop the problem. Is there a way to isolate wheter it is the left side ABS speed sensor or the contol module?

 

I would think you should have an error code, but I'm not sure.

Do you still have the speed sensor you pulled off? Try putting it on the left side and see if it fixes it (assuming it fits on both sides... I think they do...)

 

I switched the sensors and that didn't help. I checked the teeth on the ring the sensors read. There was no obvious damage to the teeth or any metal shavings in the grease. I also unpluged the abs control module and cleaned the contacts in the connector. This didn't help either. The brakes work fine with the control module unplugged, no abs obviously, but they don't pulse.

 

It sounds like you have a bad caliper. The driver side caliper being bad would cause your truck to pull to the left, and a problem like that would not be very noticeable at a faster speed. Your rotors would be moving too fast for it to catch enough to pull the truck to the left.

You say you have replaced it, but maybe its a sticky caliper.

 

WOW... where to start... so you suggest that at higher speeds the rotors and pads no longer have friction??? There are only 2 types of friction - static (not moving) and dynamic (moving). There is no such thing as super-dynamic friction that would cause different behavior at high speeds.

Nice theory, but no... thats not it...

He has already said that the pulling the ABS fuse will stop the problem, so it has to be in the ABS system. He changed the speed sensors, so its probably the module. Sorry to say it... you could try changing it yourself, but I would take it to a Ford Dealer first... perhaps its just a software issue and they can check/reprogram it.

good luck!

 

Hi Matthew, thanks for your help and suggestions. I have come to the assumption that is my contol unit also. There is not much else in the system left that it could be. Friday afternoon a Ford tech is going to look at the module and see if they can get any codes out of it. It was explained to me that the module doesn't talk well with the main computer and it can also store codes. ?? Worth a try.
Thanks

 

No... but awesome pulling out all the physics stuff. It wasnt a theory at all, and I never mentioned created some new form of friction. But what you ask makes no sense at all put up to what I said and it was quite outlandish. If there was no friction between the rotors and pads then how would he stop AT ALL aside from letting the truck slow itself down? Momentum which will be greater at higher speeds would keep him from noticing the pull as much. Its WAY easier for a caliper to catch at low speed. Do you really think its going to catch on a rotor while you are going 70mph or even allow it to catch at all? I can imagine that would be a really rough stop. And just so you/he knows.. A new ABS module is extremely expensive. After all, it is his money and therefore his choice. Maybe you are right, and im not saying you are wrong. Just dont be so quick to over look the simple things. The simple things can come back to bite you in the butt sometimes, and by the time that happens you will be kicking yourself.

 

Took the truck back to see the Ford techs and came to the conclusion it is the control module sending bad signals to the wheels. I put the fuse back in and removed the smaller of the two wire connections to the module. This made the brakes work normally and not pulse or pull to the left. I think I am going to leave the issue in this state for awhile. Thanks for the help and suggestions.