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Discussion Starter #1
2000 Hyundai Elantra. The brakes lock up intermittently in stop and go traffic. I removed the front tires. The brake pads were locked solid and the rotor wont rotate at all. Brake and wheel were blistering hot. Front driver side was hotter than front passenger. Note that brake master cylinder and reservoir are closest to the front driver side. When the wheel/brake lock up, the brake pedal is stuck at the up position. Pressing with all my might wont make the brake pedal go down. The car struggles to move forward or backward when it happens.
15 minutes after turning the engine off, the brake pedal would go down a little bit. After 30 minutes everything becomes normal, the brake pedal goes down and up normally, the car drives normally afterwards for the rest of the day.
This is happening for the last few months. The engine also runs louder than before. Rotating the steering wheel to the right diminishes the road noise slightly.

People gave me a whole list of things that could be causing this. After this locking issue started happening, over the last few months I replaced the following parts:

1. New brake pads and shoes on all 4 with new hardware.
2. New rubber brake hoses in both front brakes.
3. New wheel cylinders in both back brakes.
4. New caliper with piston assembly in front driver side. Passenger side is fine.
5. New wheel bearing in front driver side (there was visible smoke from front driver side wheel when it first happened). Other bearings are fine.
6. New cheap Chinese tires on all 4.
7. Bled a large bottle of new brake fluid through the system.

None of the above fixed the problem and I am running out of $$ and ideas. Any ideas what may me be causing this brake locking issue?
 

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Tires? Just randomly throwing money at a problem is the worst way to fix things. It makes the part shop people happy but eventually you're going to empty your wallet. I don't have a solution to offer just the advice that randomly picking parts and replacing them hoping you find the solution is a bad idea.
 

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The car doesn't have abs does it? If so maybe try pulling the abs fuse or disconnecting the harness to it and take it for a test drive, carefully, given the weather.

You also aren't noticing any weird electrical anomalies are you? I only ask because someone else had a suspiciously similar issue happen, only they also had a cel describing high power draw. Not sure where the thread is, but I was thinking the two issues could be related.

Or maybe the issue is purely mechanical in the abs manifold. Either way I'm thinking the abs is at fault here in some way.
 

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When my master brake cylinder failed, it locked up all four brakes.
The front two burnt up. The brake pedal was up all the way.There was nothing I could do.
Parked it for an hour and the brake feel came back but needed to overhaul brakes.
A couple of new lines and a new master cylinder. Rotors and pads. ... so , so , much money later.
It was replaced and everything was normal again.

So, I would flush the brake line to see if there is anything in the line to cause this situation
If that doesn't fix it then a new master cylinder may be in need??
 

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Discussion Starter #5
Tires? Just randomly throwing money at a problem is the worst way to fix things. It makes the part shop people happy but eventually you're going to empty your wallet. I don't have a solution to offer just the advice that randomly picking parts and replacing them hoping you find the solution is a bad idea.
I agree with you. But, the local mechanics are just guessing. They are not sure what is causing it. One mechanic was very sure that it was the collapsed rubber brake hoses creating a check valve. I replaced those. Then next mechanic said it must be the wheel bearing... That's how it's going now, mechanic after mechanic, parts after parts.
 

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The car doesn't have abs does it? ........... Either way I'm thinking the abs is at fault here in some way.
This car does not have ABS.
I personally know a lot about electrical and electronics devices and this is not related. It is a mechanical issue.
Is there an easy way to test a failing brake booster?
Can it be a brake booster check valve issue?
 

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Discussion Starter #7
When my master brake cylinder failed, it locked up all four brakes.
...................
So, I would flush the brake line to see if there is anything in the line to cause this situation
If that doesn't fix it then a new master cylinder may be in need??
Thanks for the comments. I'll do a brake fluid flush at home and update. It is already very cold in Chicago.
Replacing the master brake cylinder is something that is outside of my skill set. That is also one of the last and expensive things on my "parts to be replaced" list. Is there anything else that could be causing this?
 

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Discussion Starter #8
This is no longer an intermittent issue, it happens everytime after a few miles

......
You also aren't noticing any weird electrical anomalies are you? I only ask because someone else had a suspiciously similar issue happen, only they also had a cel describing high power draw. .......
I noticed the brake gets so sensitive that the car stops before the brake travels far enough to activate the brake light switch. Can the pedal automatically lose adjustment after 17 years of use?
 

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Discussion Starter #9
It is no longer an intermittent issue, the brakes lock every time after a few miles. I touched the front driver side lug nuts and they were sizzling hot. Front passenger side was not as hot. Back nuts temp were normal. I also noticed the brake gets so sensitive that the car stops before the brake travels far enough to activate the brake light switch. Can the MC and pedal automatically lose adjustment after 17 years of use? How about a warped rotor on front driver side, can it cause such locking?
I still have the original MC and pedal and no one adjusted those ever. My vacuum booster also has a proportioning valve attached to it. Do I have to move the proportioning valve in order to remove the MC to check the pushrod clearance?
I tested the vacuum by pressing the brake pedal several times with the engine off and then holding the pedal down. Then I turned the engine on. The pedal goes down fine when the engine starts and creates the vacuum.
 

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I had a longer post, but the site timed me out, so I'll just write part of it.

Take a look at the reservoir cap, if it's not puffy/swollen, then that means there is no contaminated fluid in the system, which would cause the symptoms you described. Only thing I can think of is to do what avisitor suggests and replace the MC. Thanks to the age of the car they can be had for about 30 at the lowest, brand new. Install should be about an hour. And by what you described it sounds like the booster won't need to be replaced since it's doing it's job when the brakes do work. It wouldn't cause the locking brakes anyway, not even the check valve failing.
 

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Discussion Starter #11
I had a longer post, but the site timed me out, so I'll just write part of it.
Take a look at the reservoir cap, if it's not puffy/swollen, then that .........king brakes anyway, not even the check valve failing.
The cap is in good condition, not swollen. Fluid contamination is very unlikely. I personally flushed the system in summer. According to another poster, it might be a 17 year old push-rod adjustment issue which surfaced due to the age of the MC and the car. I was suggested to unbolt the MC when it occurs to see if it releases the locked brakes. What do you think?
 

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Discussion Starter #12
I had a longer post, but the site timed me out, so I'll just write part of it................. brakes anyway, not even the check valve failing.
If you look at the photos I attached on the last post, the check valve seems to be built-in to the vacuum booster and not replaceable as a solo unit.
I flushed the brake fluid and bled all four brakes yesterday. I'll keep you posted.
 

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Discussion Starter #14
It was indeed a contamination issue. I bought Walmart brand brake fluid and cleared out the old fluid on all 4. The car is running normal since December of 2017. I think it was an act of sabotage by the oil change place I visited (long story).
 
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