I have a 2004 Sienna that seems to have continuous problems with irregular braking. It just always seems to brake irregullarly after the brakes warm up. It get a periodic pulsing to the braking force that can get rather annoying. I can reduce the problem for short time by applying the brakes firmly several time in a short time as done for "bedding" the brakes. But, it never seems to last. The next time I use the van, by the time I get the few miles to the freeway, it is showing up significantly again.
I replaced the disks and pads in the front a year or 2 ago. The problem still occured. I recently had a problem with the parking brake sticking, and ended up replacing the rear disk/drums, pads and shoes, and both read parking brake cables. I had replaced the front left caliper a couble years ago. And after the surging brakes problem re-occured after the rear brake rebuild, I started checking the temp of the disks (HF cheap IR scanner) after I stopped at the end of 14 mile drives, and found that the front right disk was alway significantly hotter than the others. So, I replaced the right front caliper. That did seem to cool that one significantly but it was still hotter than the others. At the same time, the left rear was always somewhat hotter than the right reak disk.
So, I thought, maybe there was a bubble in the lines causing 1/2 of the system to work harder, so I tried to bleed the front left brake (had done the right rear in the rear end rebuild). Well, the bleed nut on that caliper was rusted, and broke off trying to loosen it. So, I replaced that caliper again (on the O'Rielly's lifetimne warrantee).
The problems remain. the right disk ends up hotter after every trip, and the irregular braking repeats. I pull into the driveway, check the temps, and the right front dist will be over 200 F, where the others will be in the 140F range (gentle driving) by the time I get out and check it. The rear left now is only a little hotter tha the rear right disk, but still warmer. The right front is 50F or more hotter than the others in any case.
The hotter disk makes me wonder if that is most of the cause of the surging problem. Not all of it, because I frequently notice a lighter surging at the the same rate but different timing for a double surge, so more than one wheel is getting involved.
If you can offer any suggestions for why I have these problems, or solutions to them, I would greatly appreciate your help.