Repeated Brake Failure 07 Scion Tc [UPDATED]

More
2 months 1 week ago - 2 months 1 week ago #201872 by Pav_Sul
This is the update to the original post, that I made 2 months ago. This is the original post, see bellow for updates. Thank you ahead of time for the input.

Pav_Sul wrote: Hello everyone, first of all I want to thank you for any advice you might have as I am out of ideas.

I have a 2007 Scion Tc 2.4L automatic, 135k salvaged and rebuilt at 45k. About 2-3 years ago I started having problems with my brakes, first a squishy pedal and then a seized caliper. Over the last 3 years I have replaced 2 master cylinders, 3 front calipers, 3 rear calipers, 2 brake hoses. I get a seized caliper every 6 months almost on the dot.

Some of the work was done by a Toyota dealership when I got frustrated and desperate, and some work was done by a reputable local shop and some of the work was done by me. People that have worked on this car have more experience working on Toyotas than I've been alive and they haven't seen a Toyota fail 2 master cylinders in 3 years.

I am writing this because my rear caliper seized up on my way home last night yet again.

I am going to try to list as much as I know:
Brake fluid is normal (yellowish, but not new)
Pedal feels squishy, like there is air in the system.
Rear passenger side caliper is seized
There is no fluid loss under the pedal or under the hood.

Master cylinder was replaced almost exactly 1 year ago with the driver side brake line, hose and caliper.
Front driver side caliper was replaced (seized) 6 months ago, system was thoroughly bled.

I am going to take a closer look this weekend, any ideas on what I am missing? I don't want to sell the damn thing because I don't know if it's safe, the dealer isn't going to give me shit for it because it's a rebuilt title and fixing a seized caliper every 6 months is still cheaper than a car payment.

Thank you everyone,

Pav


After a busy couple of months I finally had enough time to take apart the car and diagnose, it's was also impossibly cold in the Midwest, I don't have electricity in my garage.

Update:
Fluids: brake fluid is clear/yellowish, I found no leaks after pumping the brakes and checking all fittings. No fluid under the brake pedal.
Calipers: all caliper pins are free at all 4 tires, no rust and the original grease is still wet. Both rear calipers were seized, and I broke my C-Clamp pivot trying to compress one of them.
Master: No fluid leaks at the fittings. I pulled the master, the compression and decompression is not smooth, decompression specifically feels like the master gets a little stuck. I ordered a new master.
Booster: In the car test, holds vacuum, tested by pumping the brakes and the pedal getting harder and stays harder. Vacuum valve was tested when booster was pulled by trying to pull vacuum through it, works at it should.
Booster/Master push rod clearance: the clearance in the manual reads (0 mm), I measured a 1 mm clearance gap between the booster and the master.

This was measured using a vernier caliper. Basically following the instructions in this video:

  1. I measured the depth of the booster rod from the booster face surface (datum).
  2. I measured the distance from the master mount surface (datum) to the master hole entrance.
  3. I measured the depth of the master hole from the hole entrance
  4. I subtracted value in step 3 from value in step 2 to get the distance of the master rod from the mounting surface (datum)
  5. The difference between value in step 1 and value in step 4 was 1mm
  6. Yes I accounted for the thickness of the ruler I used to help measure the depths.

My question, could the 1 mm clearance (not interference) cause the master to fail and the rear caliper to seize?

What else am I missing? What else should I check?

Again, thanks for your help everyone.

-Pav
Last edit: 2 months 1 week ago by Pav_Sul.

Please Log in or Create an account to join the conversation.

Advertisement
  • ToyotaKarl
  • ToyotaKarl's Avatar
  • Offline
  • Moderator
  • Moderator
  • Mulletude
More
2 months 1 week ago #201884 by ToyotaKarl
Replied by ToyotaKarl on topic Repeated Brake Failure 07 Scion Tc [UPDATED]
Since you have replaced everything but the brake lines and you said this was a Salvage automobile. I would trace all those brake lines under the car for any bends or kinks... Perhaps disconnect them altogether and see how well compressed air can go through them...

Not much else I can help with that you have not already replaced.

Good luck...

-Karl

Just because it is legal, doesn't make it right....

ASE Certified Master Tech

Please Log in or Create an account to join the conversation.

More
2 months 1 week ago #201887 by Pav_Sul
Replied by Pav_Sul on topic Repeated Brake Failure 07 Scion Tc [UPDATED]
Karl,

Thank you for the input, I've got a couple of days until the replacement parts come in. I checked the lines under the hood when I was looking for leaks, and they all seem okay.

Tomorrow I am going to follow the lines back from the rear calipers as they seem to seize up first. Today I checked the e-brake (cable to drum) shoes and they are within spec and adjusted properly.

I don't have electricity in my garage, so I don't have an air compressor, any other way I can test for plugged lines?

-Pav

Please Log in or Create an account to join the conversation.

More
2 months 1 week ago #201895 by Tods213
Replied by Tods213 on topic Repeated Brake Failure 07 Scion Tc [UPDATED]
Sounds like contamination. Have you tried taking the siezed caliper apart? Inspected the inside for rust or a swollen o-ring?
At this point, I'd say destroying a good caliper core, if necessary, is worth the insights you'll gain.

Please Log in or Create an account to join the conversation.

More
2 months 5 days ago #201923 by Pav_Sul
Replied by Pav_Sul on topic Repeated Brake Failure 07 Scion Tc [UPDATED]
I wish I saw this before returning the cores. I will keep that in mind if this happens again, and I have a feeling it will.

The couple of things that I noticed while working the last couple of days.

The booster when installed and the brake pedal is pressed to the floor, the rod is not centered in the booster bore.

And the front right caliper had small signs of rust in the fluid, though I am not sure if the rust was just being picked up from the inside of the valve.

Please Log in or Create an account to join the conversation.

Advertisement
More
2 months 5 days ago #201926 by Tods213
Replied by Tods213 on topic Repeated Brake Failure 07 Scion Tc [UPDATED]
The rod not being centered in the booster wouldn't be the cause of various parts seizing and failing. At worst, it could leave your brakes applied but that would come with a host of other symptoms you've not mentioned. I should think you most likely have a degraded part in the system spreading debris throughout. You would be surprised how much is left in a system even after a great deal of bleeding.

Please Log in or Create an account to join the conversation.

Time to create page: 0.247 seconds