Mechanics

LOW BREAK PEDDLE

1994 Toyota Corolla

Brakes problem
1994 Toyota Corolla V4 Two Wheel Drive Automatic 124000 miles

I have owned this car for 9 years and about a month ago the break peddle started going almost all the way to the floor. I checked the break pads, they were still at about 80% of the original thickness. Checked the rear pads and they are still fine. Blead the lines and had the same low peddle height. Replaced the master cylinder (bench blead it first) and reblead the entire system. It seemed to make a little differance. Tested the power break booster, it failed so I replaced it (adjusted the break peddle to the max height and the push rod to the no clearance spec recommended) and reblead the system again. It made no differance. Replace the wheel cylinders, readjusted the rear breaks, and reblead the system again. No differance. So with the only thing not replaced being the break calipers, I replaced them also and again reblead the system. All this has made no differance. I thought with all the things I replaced that some air might have gotten into the master cyclinder so I bench blead the master cylinder again and reblead the system again. I've done this stuff to plenty of other vehicles in the past and have allways had possitive results. At this point I don't know what to do. The paddle goes down to less than a 1/4" from the floor. Am I missing anything?
AD
Avatar
JimCarlin
December 2, 2007.



Hi there,

It is time to go back to basics. Try and get hold of 3 brake hose clamps. Lock off the 2 front flexible hoses and the rear flex hose. Now try brake pedal. If high and hard problem is down stream of clamps. If pedal spongy and will pump up, air in system. If pedal travel is still exercise problem in push rod length, or master cylinder not returning to top of stroke. Try these tests and report findings.

Mark (mhpautos)
AD

Mhpautos
Dec 3, 2007.
Hi Mark,

Thank you very much for your response and tutelage. I did what you suggested. With the hoses clamped, the pedal is hard and high. I removed the clamp from the rear hose and the pedal was still good. I clamped off the rear hose again and unclamped the front hoses and the pedal went almost to the floor.

The problem is obviously in the front. As I mentioned in my original post, the calipers are the last parts I replaced and the pedal didn’t change after replacing them. I’m sure it’s possible that the new calipers could be bad but what else do you think it could be?

Tiny
JimCarlin
Dec 7, 2007.
Hi there,

Good to hear of the progress, I feel that there is still air in the calipers as even if the calipers were seized you should still have a hard peal. Re bleed each side carefully and make sure that the master cyl stays at least 1/4 full all the time. Try this and report back.

Mark (mhpautos) : D

Mhpautos
Dec 7, 2007.
SUCCESS!

Thanks Mark. It ended up being a few things. Here’s the scenario: 1. Bleeder screws in the rebuilt calipers were mushroomed on the tips, most likely not seating correctly & letting air back in.
Fix – replaced them with ones from old calipers, working fine
2. Brass seals supplied with the new calipers were too thick and were blocking the flow of fluid going into the calipers.
Fix – replaced them with original seals, working fine
3. Sliding stud it right side torque bracket seized up causing excessive travel in the caliper.
Fix – Soaked bracket in creosote until the stud was freed up, cleaned cylinder & stud, greased & resealed, bleed calipers. Working perfectly.

Thanks again for your help.

Jim

Tiny
JimCarlin
Dec 15, 2007.

AD