2003 Toyota Highlander with 145,000 miles. Problem: 75% of the time when braking (mostly in town driving) the brakes start to grab - almost like the assisted brake system is trying to kick in. Our local dealership and another mechanic have used sensors/monitors to figure out what’s happening and unfortunately it doesn’t happen long enough that they can diagnose the problem although they say the abs is o.k. - it might be a tire sensor but they can’t confirm that. Has anyone had this problem and if so, how did you solve it?
Could it be rust on the rotors? Does it only do it early in a drive?
Here’s an idea: There’s four rubber hoses, one for each wheel, that connect the chassis-mounted brake lines to the wheels. They have to be flexible b/c the wheels move in relation to the chassis. Those hoses can collapse( internally, you can’t see it) over time due to all the flexing they have to do, and when that happens they can become a sort of a one-way valve. You press on the brake pedal and the car slows, but when you release the brake pedal the brakes remain on, and the car continues to slow, seems like grabby brakes. But the problem is actually the rubber hose is old and worn out. Sometimes when this happens the brakes will be partially applied all the time which makes the wheel heat up when the car is driven, so one test you can do is feel (careful might be very hot) each of the wheels after a drive. If one is markedly hotter than the other 3, that’s a good clue the brake hose has collapsed.
Does this happen right before you come the car is completely stopped?
Try to inspect if the pistons are sticking.