Hello all,

Let me preface this with, I have searched this forum and have not found any posts with related issues. So here we go, I have a 2011 Navigator that has been well taken care of. Yesterday my wife told me there was an issue with the brakes. The red brake light stays on and she said it feels like there is pulsing in the pedal. I asked her how hard she was stopping when she felt the pulsing? I got the GGF look if you know what I mean... Ok, so I go take the truck for a drive to see what's going on. I started the truck and released the parking brake, sure enough the red parking brake warning light stayed on. I pushed the parking brake pedal as far as I could and released it again, making sure my foot and leg were not in the way. The light stayed on. OK so that's a problem. Message window says Check Brake System, yup figured that's what the light meant.
OK, so during the drive I applied varying amounts of brake pressure at different speeds. There is pulsing in the pedal as if the ABS was being activated, however the intensity of the pulsing was not consistent. It would be stronger, or lighter, depending on how hard I applied the brake. I'm thinking the ABS was being activated however, I felt smooth braking in the vehicle as if the ABS was not activating. That seems strange to me. I also inspected all four brake rotors, the left rear is wearing differently than the others. It almost appears like it is metal on metal, but the pads have almost half an inch of material on it. The truck does not pull to one side as if one of the brakes was grabbing harder than the others. There are no strange noises coming from the brakes when applying brake pressure. I checked the fluid level and it is just under the max fill mark.
Any help, or advice, y'all have is greatly appreciated.

 

Do you have forscan? You can monitor the wheel speeds of each ABS sensor. That will rule out the ABS system(and this may not throw a code either, because the ABS computer thinks there could be legit lockup).
There is also lockup impending, where the computer can think you are locking up due to the wheel speed readout, the ABS effect could be more subtle.

 

I do not have Forscan unfortunately.
I would think if the ABS computer was thinking there was any type of lockup and it activated the system I would feel more than a pulsating in the pedal. You'd think you would feel it in the way the truck was stopping, not just the pedal. That's what is throwing me for a loop. I know what it feels like when the ABS system is activated for real in this truck. What I'm feeling now isn't it.

 

Brake light usually stays on if the parking brake sensor switch is shorted or there is low brake fluid. Guess that eliminated. There could be a simple wiring issue somewhere, but generally that should not affect braking if the fluid is full.

Pulsing then could be a very warped rotor. Also check the wheel bearings.

From what I understand, ABS COULD reduce pressure if it feels lockup is imminent. That could give a slightly different feeling than full lockup. I read an article long ago that when they design a braking system, the friction material of pads is matched to the ABS calibrations. Everything has to work together very precisely.

If it locks, then it can start pulsing to the point you feel it hard. But there are other modes. Depending on all the wheel sensor inputs, it could make that call. Like, for example, 1 wheel is dropping speed a bit faster than the others because of a bad sensor. Assuming you eliminated all base brake issues (pads, rotors, fluid, master cyl) next is get an ABS scantool. Maybe someone else will have more input.

 

Another thing you can do is disable ABS by pulling the fuse. That will eliminate that from the equation.