Both front calipers seizing? - Toyota 4Runner Forum

RandyBobandy · 02-19-2020, 05:14 PM

Went on a test drive after finishing my 5 speed swap and both of my front calipers seem to be seizing, however when I jack up the front end with the vehicle off, if I hit the brake pedal they both unstick, I took off one wheel and compressed the pistons in the caliper and they move freely, no signs of sticking, and it doesn’t happen when driving around in the driveway just when I get on the main road.

Is this a problem with my master cylinder? The pedal feels normal. These are 199mm tundra brakes if that matters

Edit: this is a 97 with the older style master cylinder assembly and not the newer one that is one unit with the booster

nissanh · 02-19-2020, 06:08 PM

I think the return lines are blocked. Could be flexible hoses and/or the return valve on master pump. You can remove and clean the master pump but DO NOT let your ABS pump to run dry.

Also check the hub bearings. Those might have a free play.

RandyBobandy · 02-19-2020, 06:32 PM

The flex hoses are relatively new, maybe 10k miles on them, as well as the hard lines at the caliper, would the master cylinder be the likely culprit as both are seizing at the same time? Rear brakes seem unaffected.

How do I prevent the ABS pump from running dry if I remove the master cylinder? I’ve never really messed with the ABS system

I should also add that the brake pedal was replaced with the smaller manual pedal during the swap but I didn’t touch any adjustments, just swapped in a new pedal, I don’t know if that could cause this issue

brillo_76 · 02-19-2020, 07:44 PM

Quote:

Originally Posted by RandyBobandy

The flex hoses are relatively new, maybe 10k miles on them, as well as the hard lines at the caliper, would the master cylinder be the likely culprit as both are seizing at the same time? Rear brakes seem unaffected.

How do I prevent the ABS pump from running dry if I remove the master cylinder? I’ve never really messed with the ABS system

I should also add that the brake pedal was replaced with the smaller manual pedal during the swap but I didn’t touch any adjustments, just swapped in a new pedal, I don’t know if that could cause this issue

If you didn't mess with the master cylinder or brake fluid. Switching a pedal would not effect that.

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RandyBobandy · 02-19-2020, 08:58 PM

I'm going to try pulling the abs fuse tomorrow and see if that does anything, If not I'll try removing the master cylinder and cleaning it

RandyBobandy · 02-20-2020, 05:38 PM

ok so I pulled the abs fuse as brillo suggested, and it didn't make a difference, however when I pulled back into the garage I got out and pulled up on the brake pedal and it instantly released the brakes, so that got me thinking that I have an issue with my brake pedal return spring, likely due to the fact that I have no clue where the end not attached to the pedal is supposed to hook to and I just hooked it to the best looking spot I could find

so would any of you be willing to stick your head up under your dash and tell me what that spring hooks on to, or post a picture if you can find one, I've been looking all over but cannot find a pic of where that spring attaches

brillo_76 · 02-20-2020, 11:12 PM

Quote:

Originally Posted by RandyBobandy

ok so I pulled the abs fuse as brillo suggested, and it didn't make a difference, however when I pulled back into the garage I got out and pulled up on the brake pedal and it instantly released the brakes, so that got me thinking that I have an issue with my brake pedal return spring, likely due to the fact that I have no clue where the end not attached to the pedal is supposed to hook to and I just hooked it to the best looking spot I could find

so would any of you be willing to stick your head up under your dash and tell me what that spring hooks on to, or post a picture if you can find one, I've been looking all over but cannot find a pic of where that spring attaches

That took me 10 pictures to get. I hope it helps

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RandyBobandy · 02-21-2020, 07:07 AM

Thank you that is exactly what I needed, I’ll fix it and update later today

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