Rodeo :: 1999 LS V6 3.2L - Brake Chatter Occasionally At A Stop

1999 Rodeo LS V6 3.2L MT 277,000 miles. Over the past few months, I've been experiencing brake "chatter" occasionally at a stop.

It seems to happen mostly on hot days, and within the first few miles of driving, but I haven't recorded that data in any detail. It's right when I'm getting to a complete stop. It's a chatter that shakes the car when applying the brakes.

I thought at first that it seemed to be coming from the rear, but sometimes it feels like it may be at the front, or maybe it's happening at both.

I pulled the rear shoes and front pads to check the pads, shoes, rotors, and drums but found nothing. I did have a frozen bolt (pin) on one of the front brake calipers, but I fixed that and it still happens, but only occasionally. Some days it doesn't happen at all, and on other days it happens a few times.

The stuck caliper pin wasn't binding the caliper, I just couldn't get the pin out, but soaking the threads in liquid wrench, tapping it, and applying a little leverage freed it up. Before that I could easily spin the disc by hand.

It has never happened in the morning, but seems to happen mostly around mid day and early evening and mostly when the day has been especially hot, which seems strange, but that's how it's been.

It isn't the same feeling as the ABS being applied in a high speed slippery situation, but it is kind of at that frequency.

It feels like the pads or shoes are chattering on the braking surface, but neither of the pads, shoes, rotors, or drums show any signs.

If maybe this is a typical symptom of a master cylinder going out? That is a central common point for all brakes. It's a 1999 with 277K miles on it and the master cylinder is original, so.....