I tried searching but came up empty; sorry if this has been asked before.

A friend has a 2006 F150 V8 XLT 2WD and is having brake problems. It is pulsing with maybe a slight grind through the pedal. Can't feel it through the steering wheel or the backside.

It was slight until he changed the wheel sensors on the front. Then it became consistent. I can;t say anything much about that part.

I drove it a few miles today and under moderate to heavy braking it is perfect. I did not brake hard enough to get close to wheel lock, but I stopped every way from very easy to pretty hard. As I said, moderate to heavy pressure, it stopped as new. But light braking is another conversation. Under very slight pedal it starts with a grinding feel through the pedal, but the feel is regularly pulses almost like the same spot in each wheel rotation, but not quite. It starts off slightly irregular, but the more it slows, the more consistent it feels through the pedal.. Push the pedal a little harder, the pulsing (grinding) is more noticeable. Harder still, it goes away completely. When it pulses, it is a bit faster when the truck is going faster, slower when the truck is going slower, but did not appear to correspond with the exact same spot on the wheel each time. But is could have, I was not trying to time that.

I want to blame the new antilock sensors, but it happened a little before and got noticeably worse after. it may have something to do with his install if there is some tricky way, something easy to miss, or maybe more than one way to install them. Not sure of the extent because I did not drive it until the problem showed up. He said it was worse after the sensors. He bought the sensors online, so I do not know the source.

Aside from new sensors, I do not know enough about ABS to even join in the conversation about what it might be.

Any suggestions are appreciated. Thanks.

 

I assume the obvious has been checked ... rotors ?

 

I asked, but not sure if he checked, probably not. But the shudder, pulsing, or however to describe it, was only felt through the pedal and not through the seat, the steering wheel, or the floorboard. It was not like any warped rotor feel that I have ever experienced, so likely not. I'll suggest he check that.

 

Tell him to disable the ABS (pull the fuse to the ABS pump) and retest. if the pulsation is still there while braking, it's a concern with the base brake system.

 

^^^ This ^^^

 

Don't mean to appear ungrateful to those who helped, but I've been AWOL for a few days down state with family. I'll relay this on to him and see what turns up. I have no experience with ABS, so I'm out of the loop here.

Thanks, and if he gets back to me, I'll report on it here. Maybe it can help someone else down the line.

 

Quick followup. My friend just called me and said it was suggested to him that the bolts (screws?) that attached the wheel speed sensor were rusty so he needed to clean the rust off. He did, put some vaseline on it, and it is getting better, almost no pedal vibration or pulsing.

That is what I hate about electrical problems, takes three weeks to find the problem and three minutes to fix it. At least it was a fix and not a buy and replace.

I'm not sure about the vaseline, though. Seems that the screw might vibrate out easier......

 

If the sensors are not getting an accrate read on wheel speed, if the computer thinks a wheel is rotating slower than others when the brakes are applied, it will pulse the brakes as if a tire is sliding or partially sliding as tires don't speed up when braking. That pulsing is the anti lock system doing it's thing to let the tires regain traction. I feels like gravels through the brake pedal.

 

Thank you for the explanation. I have never been able to figure out something by just remove this and replace it. But when I begin to understand what is going on and why, the job gets easier. That helped a lot.

Again, thanks.