Mechanics

FRONT DISC LOCKING

1993 Toyota Camry

Brakes problem
1993 Toyota Camry 4 cyl Front Wheel Drive Automatic 473, 10 miles

I recently replaced the pads, brake hoses and calipers as well as the proportion valve. However, the left pads are locking when applied but will not release. The brake pedal gets very hard and locks the wheel. After a while when the car cools down the brake releases.
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Ck1
October 7, 2010.



The first thing I would suspect is the proportoining valve.
Then, I would loo at the caliper.
This is the front left caliper that is the only one locking up?
It can lock up on the shafts that the caliper slideson. Especially after it has happended once, it will happen over and over. Even if you straightenthe pin, I would think itis fatiguedand the caliper needs to be replacedif this is the case.

Let meknow howit goes and ifIcan help any furhter.

I have replaced both calipers with new ones and also replaced the proportioning valve, but the problem has not been resolved. I'm thinking master cylinder. What do you think?

Tiny
Ck1
Oct 7, 2010.
If the master cylinder were the culprit, I could see the seal being seated incorrectly and closing over the port and not releasing the pressure built up. However, This would affect both front brakes or both back brakes.
Again, this is the front driver's side claiper, correct?
That is the closest to the master cylinder. Keepthat in mind as we go through this. Not that I know that it is part of the puzzle.
Did this happen as soon as the brakes were done and you first used them?
If not, how long before this happened?

Let me know and I will think some more about it.
By process of eleimination, you are kind of getting down to the master cylinder aren't you?
However, make sure that the cliper that is locking up get checked over or replced as the pins it floats o arre probably bent and the pads are ertainlydamaged.

I will check backlater.

I was able to drive the car for several days before the problem reoccured after changing the caliper. I later changed the proportioning valve and then after driving approximately 40 miles the same left front locked again. I was told that the new caliper could be defective. I did not get to the master cylinder yet as it is only the one side that has the problem. I'll replace the caliper again and see what happens.
Thanks for the input.

Tiny
Ck1
Oct 8, 2010.
Before the problem reoccured, how long after the first caliper was put on before it had its first failure?
Was it an orignal caliper on the car or one tht you had put on that failed.
I just want to really clarify, communicating by text is not easy, so we don't misunderstand each other.
So forgive me if I ask things I have already asked or that may seem already evident.

So, first before you started working on the brakes and the system was from the factory, if it was not the original let me know, were there problems with the caliper then?

If not, I am assuming and correct me where I am wrong, part of the brake project that you originally did was the following; Both front calipers

Front brake pads
Are the rear brakes drums or pads? Were the rear calipers/wheel cylinders replaced at that time?

Rear pads/shoes

System fluid was replaced and bled starting at the passenger rear, then drivers rear, then passenger front and lastly drivers front. This is order of farthest to closest from master cylinder.

Then the 1 caliper locked up. After a period of time it freed up. How long before it locked up again and how did the brakes perform before that happened?

Then the proportioning valve was replaced. The caliper that was locked was not replaced. Did you inspect it and if so what did it look like?

Then locked again, same questions as above?

I am sorry about the redundancy. I just want to understand the timeline and what was replaced or failed and when in this sequence of events.

I think you will certainly have to replace the caliper, but I think that if it was remanufactured it probably has a warranty. So, try to get another without paying for it.

Hold off on replacing it because if I understand correctly, you have purchased 2 calipers that were defective. The odds are slim on that.
There is something else going on and I would hate to see you install another caliper and have it lock up.

I will check back soon. It will work out.

I appreciate the throughness of the questioning so no problem there. Here's the sequence-: 1. Change front pads, left front starts locking.
Change/replace left front caliper and brake hose.
2. Left front starts locking. Change/replace caliper and hose.
3. Left front starts locking. Replace proportioning valve.
3. Runs well for two days approximately 50 miles driving in different segments.
4. New left front caliper starts locking again, rigt side is working fine. Replace this caliper with a new one.
5. Drive three separate occassions approximately 50-60 miles total.
Problem reoccurs except this time the new right caliper is locking.
As you mentioned, I am doubtful that I got two bad calipers so I am puzzeled.
The rear brakes are drum with shoes that were replaced about two months ago. I had no problems with the rear brakes since the change.

Tiny
Ck1
Oct 11, 2010.
On my previous reply, #2 should be the Right front starts locking.
I'm wondering if there could be a problem with the pads overheating and sticking to the rotor? Strange thought but I'm not sure what else to look for.

Tiny
Ck1
Oct 11, 2010.
I do not think that the pads are the source unless you got something defective or really cheap. Just increasing the likelihood of a defective issue. In either case, I agree it is odd and is probably not the reason for the problem.
I would not rule it out, but something in the caliper is more likely.
Unfortunately, now that it has locked up once, the original reason that caused it could be covered by the damage that the locked caliper has caused to the pads and caliper.
I would get a new caliper through warranty and buy a new set of pads. However I am apprehensive to install them as of yet because if they were not the original source for the problem, they will be damaged and need replacing again without gaining any insight into the source of the problem.

I am going to do some research and put some more thought into the issue.

Go ahead and try getting replacements through warranty, but don't install them until we can get some more insight into the problem. You should only have to carry the core cost on the caliper for a while.

I will get back with some answers ASAP. Let me know what you find out and we will get you there.

I found somethhing strange in the slide pins/bolts. The ones in the second replacement caliper kit were different from the original as well as the first caliper kit. When I checked the right side caliper replacement pins/bolts the upper one is also different and was very difficult to remove although well greased. I'm going to switch those pins/bolts with the original ones and see if that makes a differance.

Tiny
Ck1
Oct 12, 2010.
I will be checking the posts as much as I can untill I see what comes from changing the hardware issue you found.

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