Brakes locking up

[BlazerBud]

My Blazer is fine,

I bought a cheap 1991 MX-6 Mazda for just driving to work.
I have a question about brakes. I'm sorry this is long, someone please give me some advice.

This car was parked for a while, I think it was sold as a repo from a pawn your title place. The price was right so I got it.
It drives fine, but I have only had it two days, and every day after about 20 minutes of driving the brakes lock up and the pedal gets hard, like no fluid can get get drained back to the reservoir. Each time I had to creep in first gear with the brakes smoking to a parking lot where I could bleed the brakes. All 4 wheels get locked not just one, the front hold worse than the rear obviously. Bleeding just one caliper frees it all up though.

Here is what people have told me:

1. There may be water in the lines. This may be true, the last time I bled them it was so hot, that mostly steam came out.

2. One guy said the master cylinder may be getting fluid behind the piston. I don't know much about the validity of this.

3. One guy said an old brake hose can get frayed inside and act like a check valve, preventing fluid from getting drained back to the reservoir. This would be evident if only one wheel locked up. I don't think I have experienced this.

4. One guy said the brakes were likely dirty when parked, and rusted up. He said it may be cause. This is probably part of the issue.

5. I think the fluid was crap, I have bled about a quart through the system draining each caliper individually. I think I should flush about a gallon through it all. The only real noticeable thing is that the pedal feels like there are several distinct places in the travel of the pedal where it feels like notches, I was worried that this may mean junk in the piston or bad seals in the piston.

 

[jonrpick]

My Blazer is fine,

I bought a cheap 1991 MX-6 Mazda for just driving to work.
I have a question about brakes. I'm sorry this is long, someone please give me some advice.

This car was parked for a while, I think it was sold as a repo from a pawn your title place. The price was right so I got it.
It drives fine, but I have only had it two days, and every day after about 20 minutes of driving the brakes lock up and the pedal gets hard, like no fluid can get get drained back to the reservoir. Each time I had to creep in first gear with the brakes smoking to a parking lot where I could bleed the brakes. All 4 wheels get locked not just one, the front hold worse than the rear obviously. Bleeding just one caliper frees it all up though.

Here is what people have told me:

1. There may be water in the lines. This may be true, the last time I bled them it was so hot, that mostly steam came out.

2. One guy said the master cylinder may be getting fluid behind the piston. I don't know much about the validity of this.

3. One guy said an old brake hose can get frayed inside and act like a check valve, preventing fluid from getting drained back to the reservoir. This would be evident if only one wheel locked up. I don't think I have experienced this.

4. One guy said the brakes were likely dirty when parked, and rusted up. He said it may be cause. This is probably part of the issue.

5. I think the fluid was crap, I have bled about a quart through the system draining each caliper individually. I think I should flush about a gallon through it all. The only real noticeable thing is that the pedal feels like there are several distinct places in the travel of the pedal where it feels like notches, I was worried that this may mean junk in the piston or bad seals in the piston.

Replace or rebuild the MC, completely bleed the system dry, then replace with all new fluid.

Option #2...not sure if it'd cause the problem, but when the piston doesn't seal well, fluid will creep past, hence the rebuild or replace idea.

 

[BlazerBud]

Is it more expensive to replace the MC or difficulty to rebuild?

 

[Jason4x4]

My Blazer is fine,

I bought a cheap 1991 MX-6 Mazda for just driving to work.
I have a question about brakes. I'm sorry this is long, someone please give me some advice.

This car was parked for a while, I think it was sold as a repo from a pawn your title place. The price was right so I got it.
It drives fine, but I have only had it two days, and every day after about 20 minutes of driving the brakes lock up and the pedal gets hard, like no fluid can get get drained back to the reservoir. Each time I had to creep in first gear with the brakes smoking to a parking lot where I could bleed the brakes. All 4 wheels get locked not just one, the front hold worse than the rear obviously. Bleeding just one caliper frees it all up though.

Here is what people have told me:

1. There may be water in the lines. This may be true, the last time I bled them it was so hot, that mostly steam came out. Not Likely

2. One guy said the master cylinder may be getting fluid behind the piston. I don't know much about the validity of this. Could be a bad master, since it is all 4 locking up.

3. One guy said an old brake hose can get frayed inside and act like a check valve, preventing fluid from getting drained back to the reservoir. This would be evident if only one wheel locked up. I don't think I have experienced this. Correct, would cause one wheel to lock up

4. One guy said the brakes were likely dirty when parked, and rusted up. He said it may be cause. This is probably part of the issue. It would do that from the start, not once warmed up

5. I think the fluid was crap, I have bled about a quart through the system draining each caliper individually. I think I should flush about a gallon through it all. The only real noticeable thing is that the pedal feels like there are several distinct places in the travel of the pedal where it feels like notches, I was worried that this may mean junk in the piston or bad seals in the piston.

Flush the fluid till it comes out clean, also, If someone has replaced the booster in the car, the rod on the pedal or inside the booster that pushes the master could be out of adjustment, causing it not to release all the way.

 

[BlazerBud]

Thanks guys, I think I got it straight now. Autozone has re-man master cylinders for $36 after core is turned in. I'm gonna start there, then drain the whole system, purge it all out with fresh fluid and see what happens. I think the comment about the symptom where it only gets bad after it is warmed up vs. being bad all the time means it has to be a bad master cylinder and not just crap in the lines by itself.

 

[jonrpick]

Thanks guys, I think I got it straight now. Autozone has re-man master cylinders for $36 after core is turned in. I'm gonna start there, then drain the whole system, purge it all out with fresh fluid and see what happens. I think the comment about the symptom where it only gets bad after it is warmed up vs. being bad all the time means it has to be a bad master cylinder and not just crap in the lines by itself.

That's a good plan of action. Even if it doesn't fix it, you have the benefit of new parts and elimination of one major piece of the brake system.

I'm betting this'll fix it though...

 

[jonrpick]

Is it more expensive to replace the MC or difficulty to rebuild?

Even though your buying a reman'd unit, I'll go ahead and say that rebuilding is probably cheaper **IF** you have the needed tools to do so. Add the tools and you're over the cost of that reman'd MC. A MC cylinder hone for example is $10-$15, and that's just one tool. Almost 1/2 the cost of the new MC, and you haven't even bought the rebuild kit yet.

$36 is a steal considering...