Tacoma Front Brakes Lock Up While Driving

Replace the flexible lines that run to your calipers. That's the problem 9 times out of 10.

Thank's for the info. I think what's giving me a hard time tracking this problem down is that it started as soon as I completed the rear brake job.

But if that were the cause, you wouldn't expect cracking the front brake line at the master cylinder to relieve it. Also if the flexible lines are blocked, he might have noticed something unusual when bleeding, like needing some pedal pressure.

And while you are there check the front wheel bearings for play/slop and strip down the front cailipers to make sure the piston/caliper assembly is all free to release pressure after the brakes are released.
I've always thought the absence of a positive retract spring on disc breaks is a design flaw.
Del

Disc brakes seem to manage fine without return springs. If they had them the brakes wouldn't be self-adjusting.

AROOGAH AROOGAH...SARCASM ALERT
Hang on, give me 5 minutes with a pencil and paper to design a limited travel, self adjusting return mechanism.
Oh, wait, it's already been done for drum brakes...
Del

No sarcasm intended. But a self-adjusting return mechanism would solve a problem that doesn't exist. If you think it has advantages and can design one that easily, you could do it and sell it to the car makers for big bucks. That's not meant to be sarcastic either.

Some of the early ones for drum brakes didn't work. I had a 73 Mk 3 Cortina where I had to turn the adjuster with a screwdriver every MOT plus one in between (did a lot of miles those days). That was the rear brakes, I never saw self-adjusting front drums as front discs came in about that time, but I imagine there were some about.

There are of course self-adjusting disc brake calipers where the handbrake is incorporated. I just replaced a Bosch one which had got stiff and didn't work properly. Peculiar symptoms which I can describe if anybody's interested. To see how it worked, I dismantled it, which Herr Bosch didn't encourage, eg a stud with 5-sided head in a recess. It was pretty complicated and I'll bet it took even those clever Germans more than 5 minutes to design it!

My '72 Commando has self adjusting front drums. It's the same hardware front to rear.

I am not saying they *work*, I'm just saying it has them.

The quickest and easiest way to adjust "automatic adjusting brakes" is to drive in reverse and apply the brakes off and on a few times. If the adjusting mechanism is all in place and working correctly they will cinch down to the proper setting.

The quickest and easiest way to adjust "automatic adjusting brakes" is to drive in reverse and apply the brakes off and on a few times. If the adjusting mechanism is all in place and working correctly they will cinch down to the proper setting.

If my High School Auto Mechanics class serves me, I believe thats called a star adjuster.

On the old Ford, the handbrake mech comprised a bar between the 2 shoe webs, which extended when applied. The bar was in 2 parts with a threaded section and ratchet wheel, and a hook thingy on the handbrake mech to turn the ratchet wheel when handbrake applied. As I said, it didn't work, but easy enough to turn with a screwdriver. Only prob was you had to do it with the drum off, so had to know from experience how many clicks to give it, or do it till the drum wouldn't go back on, then take it back one, which was a bit more fiddly. As the auto-adjust was via the handbrake, I don't think your method would have worked, but thanks anyway.

Star wheel...yep.

The hand brake works for adjusting too. You just sit there and set and release the brake over and over again until the brakes are tight. Of course, this only worked for the rear brakes. Reversing was the method for the front drums.

When front brakes were replaced with disks it alleviated that front adjusting method.

Most drums have a removable rubber plug on the back side which allow inserting an adjustment tool (i.e., a flat bladed screwdriver) to adjust as needed.

If I remember correctly, ^{( so check and make sure}) not to be confused with adjusting the wheel bearings.

we had a spoon-like screw driver. there is a notch behind where the drum fits on that you stick in the spoonlike screw driver.

This star adjuster, after its adjusted is suppose to make the adjustments as the pads wear as you back up.

Oh, I loved industrial arts class........... as a rural farm boy, driving a POS of a car proudly. what I pick up from that, I was able to make it home alright after car problems.

Then as it is now, other than maintenance, I always hated working on cars, and only did it when I had to. The plus side was, the feeling I had when it was done, which was "I'm glad thats done"

Del, If the caliper piston seals are OK they move the pistons away a little when pressure is released...but the wheel bearings must be adjusted to have a little bit of play and this cause the disc to push the brake pads away. Further,with no bearing play the grease is forced away from the working surface of the bearing...then it runs hot and wear fast, specially with very high melting-point ghrease.

Its actually there, but you may not see it.

The rubber seals that help keep the fluid from leaking, "stick" on the pistons and pull the pistons back a tiny amount after each time the brakes are used.

When the pads wear, the seals "slip" and then do the same thing again on a slightly different area of the pistons.....which, by the way, is the reason for only using completely original parts in any brake system.....wrong type of rubber may seal, but could cause too large or too small retraction of the pistons.

As an aside, disks and pads are usually "tuned" to each other by the OEM, to work efficiently and to get the best/lowest wear rate.

Aftermarket pads will still stop the car, but can often wear the disk at a far higher rate than necessary, wasting any savings made....

I would try replacing the front brake calipers first....

Well kiss my nasty knuckle busted hand, an actual mechanic.....lol

Could be some of us have gotten to old to bend down to do the work. Or forgotten which way to turn the wrench.

I've found that ramps get the work higher, thus easier to bend down to. Getting under is my problem due to vertigo.

SolarEagle would like to know if your daughters available to take a look at his brakes.

Good on you.

We live in a disposable world. Nobody wants to take the time to "fix" stuff.

Not everyone has the skill and knowledge to strip down, clean, reassemble. Fewer take the time.

Cheers.

When you work on antique junque, replacements may not be available. Like the oil filter for my 1943 Chrysler engine. Thus disassemble, clean up, maybe some repair, and replace may work just fine.

A while ago the master cylinder was leaking on my car and I wanted to replace the seals in it. It didn't look too hard to disassemble and the Chilton guide even had instructions for replacing the seals. While some were just O rings others were particular to this unit, I looked and looked but could not find the seals for sale anywhere, and ended up having to replace the whole thing. I hate that I had to exchange it to avoid the core charge to some company that is just going to clean it, replace the seals and resell it. Would of much rather just cleaned it fixed it and put it back in myself. For many things in cars they simply do not make it possible, to repair it yourself down to that level, and forget about electronics.

Your system probably has a proportioning valve to compensate for the two different types of brakes.

HowStuffWorks "How Master Cylinders and Combination Valves Work"

I don't know if it has been disturbed by your work, but, it's a thought.

Thank's for the info. I think what's giving me a hard time tracking this problem down is that it started as soon as I completed the rear brake job.

It could be that bleeding the brakes after attending to the rears is the cause of the problem. When bleeding we tend to press the brake pedal all the way to the floor which is a place it is seldom required to go. It sounds like the booster has suffered as a consequence. The brake place I use warns of escalation when any part of the brake system is overhauled - especially master cylinders (I note that yiou have already changed it). It is unfortunate that your home mechanical work has resulted in a high financial cost. Keep the faith.

Was the engine running when you bled the brakes?

Good answer.

Also, is one front brake locking, or both? If it is both, it is not the flex lines etc, it is somewhere in the system before the division to R & L wheels.

My money is on bigg. It might be adjustment of the master cylinder plunger - if it is adjustable.

This topic comes up every 6 months or so.

I wonder if there is some minor difference between the old and the new master cylinder and the pedal or similar is catching on something, and not returning fully. A bit of the bodywork may need to be ground away.....or similar.

Also, try pulling the pedal up, if it can be moved up, it could be that the new master cylinder is mechanically bad.....

I have also found carpets that do the same thing, that is holding the pedal down slightly..........now that is a very cheap fix....

I don't know how you guys approach it, but when I have to bleed my brakes, I always start at the farthest wheel cylinder from the master cylinder, (I always insure the master cylinder is completely full to begin with) In my case, the farthest from the master cylinder is the right rear. I have a old brake fluid can that I fill at least 1/2 full of clean brake fluid. I run a hose from the bleeder valve into the can of brake fluid, which I tie wire or nylon tie at a point higher than the cylinder being bled. (insuring that the can is higher than the wheel cylinder and that the hose is SUBMERGED to the bottom of the fluid in the can. I can then break the bleeder valve open, go pump the pedal very slowly to the floor and let it up very slowly about three times, then crawl back under the vehicle and tighten the bleeder valve, REFILL THE MASTER CYLINDER, remove the hose, and go to the next farthest bleeder valve. Empty the can and refill the can about half full with new (clean) brake fluid, tie it up higher than the bleeder valve and repeat, until all four wheels are bled. Some might say I'm putting dirty brake fluid into the can, but that is why I empty the can and put in clean fluid when bleeding each wheel. (I'm sure the purist will say that it will allow some "unclean" brake fluid to remain in the system, but then again, I don't drive a $250,000 Bentley, and if I could afford one, I should be able to afford to take it in for "proper" service. Also it is a MUST to make sure to TOP OFF THE MASTER CYLINDER after bleeding each wheel to insure that you don't suck any air into it by running it out of fluid. If you do, you can chase your tail for hours!!! The same can be said of the can of fluid at each wheel, make sure that the hose is at the bottom of the brake fluid. When letting up the brake pedal, it will suck fluid from the above mentioned can, as well as the master cylinder, preventing any air bubbles in the process, just brake fluid. For bleeding the master cylinder, push the brake pedal down very slowly for a short distance (an inch or two) and let the pedal up very slowly. Keep repeating until no more air bubbles appear in the master cylinder reservoir on the downward pressure. Make sure to keep the master cylinder full of brake fluid, and top off when completed. It does take somewhat more brake fluid than by having a "toby" to "assist" you~ (Pump it up, now hold it, OK, Pump it up, now hold it, OK, etc.) but!!!When you don't have any help, you have to improvise!! It's worked for me for years. Happy motoring.

Does the truck have 4 wheel anti-lock brakes? Was the engine running when you bled the brakes? Does the brake light come on when you experience the locking? If it does in fact have 4 wheel anti-lock brakes, try removing the fuse for the anti-lock brake system. This will not affect the performance of the brakes but will remove the chance of the anti-lock system from causing a problem.

Buy a Ford or Chevy or a Ram pickup and sell the Tacoma.

II recently had an issue with a new master cylinder where it would limit the amount o oil being returned; similar to a residual pressure valve. After a few hours of troubleshooting one day I finally checked the master cylinder and realized it was a manufacturing defect preventing the full return of the piston inside. I would recommend double checking that your master cylinder is freely letting fluid return. Could be a manufacturing flaw or the link through the vacuum booster is just aka tad long. I would pump the brakes until they lock, then loosen the mountain feet on the m.c. and see if it releases - cheaper than all the other suggestions this far.

For anyone thinking otherwise, the ONLY way to adjust wheel bearings on any car is exactly as the car manufacturer says they should be done:. Some need preloading.

Here you car will fail the TÜV Tests if there is any play/movement of the wheel/disk relative to the car, they test for that. Really carefully.....

Its also dangerous for the bearing and of course you and yours if the bearings are loose as someone here said they should be....the disk will also rub on the brake blocks if it is not held tight in the correct position....

Disk brake blocks release due to the "give" in the rubber seals, in the way they are designed and made. Its enough.

I was just getting ready to take her to the "DEALER" When I decided to give the push rod an adjustment. Cranked it back five turns and took it for a test drive, "PROBLEM SOLVED!". I still can't understand why replacing the rear shoes would have had an effect on the push rod but I'm not going to argue. Thank's to all who offered help, this is a great site! Glad I found it.

Well done Bare Tree, glad you solved it. I can't see why it happened either, but I bet you're well pleased!

I'm happy as a .......... in a ..........! Now on to the other 300 chores I was working on when I ran in to this one.

Is the pedal height correct? 5 turns seems to be a lot - you just need to have free play when pedal is up.

Dead right!! Well put.

I don't think you found the problem correctly, you have simply adjusted to to stop the problem, its NOT fixed.

On the up side, other than eventually a slightly "looser" brake pedal if the problem fixes itself, what can go wrong? You are erring on the safe side......

Something was "hanging" the brake pedal....

if your mechanic didnt loosen the bleeders when he pushed the pucks in, then its probably the proportioning valve. it should be near the the master cylinder. it splits the hydraulic pressure going to the front or rear brake cylinders. the front brakes need more pressure. it's an easy fix. or he might have ruined the check vale in the master cylinder.

The only thing we did was replace the shoes on the rear. That's why we were stumped.

a stuck emergency cable.