I started a thread about a week ago about what I thought was an ABS issue with my 2004 Ford Escape XLT.
A bit of background information: every now and then (usually when decelerating from around 35-40mph), I will get a pulsating/knocking feeling from my brake pedal. At first, I thought it was the ABS, as I was told about a year ago that the ABS tone ring was broken. The more the problem manifested itself, the more I got to study it a bit. The pulsating/knocking in the pedal is usually accompanied by a very dry rubbing sound, and both the sound and the pulsating seem to be in direct relation to the motion of the wheels. I took it to the local garage this weekend and they recommended changing out the rear brakes - this made sense to me, as they haven’t been changed out for as long as I have had the car.
Got the car back about an hour ago - on my way home, the pulsating came back when I was coasting into a stop light. FML.
The pulsating seems to have no affect whatsoever on the stopping distance of the car - a few times when it has happened, I have mashed the pedal, and the car comes to a quick stop just as you would want it to. After coming out of a complete stop, the brakes will work completely fine for a while - there seems to be no real rhyme or reason to what makes it happen.
Anyone that has any ideas of what the issue might be, or that has experience with this issue, it would be appreciated!
Intermittently Sticking/Dragging Brake Caliper(s) That Sometimes Do/Does Not Release Rotor(s) All The Way?
Caliper(s) Not “Floating” Due To Corroded Slides/Pins ?
Thanks, CSA - while I have no doubt that that truly is the common sense answer, I have to ask one more question which may or may not be dumb: are any of those problems a safety risk, or could I possibly wait to have them fixed until my bank account can recover a bit? Would these be repairs that could be done in the driveway?
@Dobb, Mind You That My Suggestion Is Only A Semi-Educated Guess And Would Have To Be Checked Out.
I Wouldn’t Think It Would Be A Big Safety Issue Unless My Suggestion Is Correct And It Begins To Drag Much Worse, Creating A Pull. Also, If A Caliper Sticks/Drags Then The Brakes Could Wear Faster (because the brake is actually applying itself while driving sometimes).
When was the last time front brakes were replaced/serviced on the vehicle and do you live in a part of the country where road salt is applied to the roads in winter?
The front brakes were changed about two years ago (give or take a few months). When I initially took it in last week for the pulsating, they did a full brake inspection. They said the back brakes were very worn, and most likely the original brakes (11 years old? Yikes!), so they are now brand new, with only about a mile’s worth of driving on them. The front brakes got a clean bill of health. I am in Michigan, so between the past two winters, the car has gone over more than its fair share of salt. This makes me think that your hypothesis about the calipers is correct. I would say that when there is pulsation in the brake pedal, it is only maybe 10-20% of the times I use the brake pedal. After I come out of a complete stop, the brakes usually work perfectly fine for the next several times I use them. There are no dash indicators, and there is no noticeable pull in the steering wheel (yet).
I’m not sure how this vehicle is equipped, discs all around, or front disc w/rear drums. In any event, I think the problem with the ABS tone ring needs to be fixed first, before proceeding with any more diagnostics.
Once the ABS system is back in good order, if the pulsating still occurs, the first thing I’d check is for warped rotors. As @db4690 mentions above, have the shop measure the run out. Drum brakes can pulsate also due to run out problems, but it is less common than discs. Still, run out can be measured for the drums too if that’s a suspected source.
re “New brakes”": A point of clarification. When brakes are serviced – for example for disc brakes – it is possible to replace only the pads. But sometimes both the pads and the rotors are replaced. And sometimes the pads, rotors, and calipers are replaced. When discussing brake work with the shop, make sure you understand which of the three has been done.
“A bit of background information: every now and then (usually when decelerating from around 35-40mph), I will get a pulsating/knocking feeling from my brake pedal.”
I agree that rotors need to be checked for run-out, but because this problem is intermittent, described as “every now and then” and because of the “very dry rubbing sound” that accompanies the “pulsating/knocking” I thought a faulty caliper could be initiating the problem. And a sticking/dragging caliper could heat the rotor and cause warping and exacerbate the run-out dimension that was suggested.
A brake inspection is where I would begin. Perhaps an uneven wear pattern on brake rotors and pad thickness comparison would provide more clues, too.