Brakes seizing on front

This is a different expert. I was asked to try to help you.

You never should have adjusted the push rod. That is the reason that the brakes are locking up. They are building up pressure because they are never relieving. You may have another issue causing your low pedal but adjusting that rod is not the way to resolve it. You need to back off that adjustment until there is about 1/4" of pedal travel before that rod touches anything.Ignore the pedal height for now. You need to get the rod correct before be look for other issues. That is a very sensitive adjustment.

OK. I restored the linkage to approx.1/4" free play before the rod has any effect on the brakes. Have bought a manual and have the correct measurements on pedal from floor. Test drove it and so far no problems. Hope it stays that way. Still wondering why it seized in the first place. I will drive it 70 miles round trip to work tomorrow and will see what happens. Thanks for the advice. Will let you know how it goes.

It seized because the master cannot relieve pressure unless it returns all the way to it's stops. Only then does it release it's built up pressure. That's why you can never remove that free play.

I'm having the same issue with my 2000 Hyundai Elantra with no ABS. But, my master cylinder is still the original one and no one adjusted the rod length on mine (which seems to be the problem for the OP). Please see below and let me know your diagnosis.
The brakes are locking up intermittently in stop and go traffic for the last few months.
I removed the front tires. The brake pads were locked solid and the rotor wont rotate at all. Front-driver side brake and wheel was blistering hot, front-passenger side was less hot. Back brakes were not hot. When the wheel/brake lock up, the brake pedal is stuck at the up position, brake becomes super sensitive, the car drags and just touching the brake stops the car. Pressing with a lot of force wont make the brake pedal go down, it stays stuck at up position for 10 minutes even with the engine off.
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.
The car also runs louder than before. Rotating the steering wheel to the right diminishes the road noise partially.
People gave me a big 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 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 intermittent brake locking issue?

Hi 2CARPROS KEN, Can you please explain how the stuck brake booster internal valve can cause the brake pedal to be so stiff and be stuck in UP position for 10 to 15 minutes and then gradually loosen up over 45 minutes? Is there an easy way to test this? Can you please point me to a good video that explains the valve/diaphragm inner workings?

Have you checked the push rod clearance from the booster to the master cylinder is there free travel? 1/8 inch. This can hold pressure on the system causing the problem you are describing. I don't have a diagram of the booster. Please check the clearance and get back to us.

It is no longer an intermittent issue, the brakes lock every time I drive for a few miles. When it was about to lock, 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 got so sensitive that the car stops before the pedal travels far enough to activate the brake light switch. Can the master cylinder pushrod and pedal automatically lose adjustment after 17 years of use? I still have the original MC and pedal and no one adjusted those ever.
How about a warped rotor on front driver side, can it cause such locking?
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 (photo)?
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.

It sounds more like the caliper needs to be replaced here is a guide to help you.

https://www.2carpros.com/articles/brake-caliper-replacement

Thanks for the suggestion but the front driver side caliper assembly (which is getting very hot) is new, replaced recently while trying to fix this issue. Can the new (rebuilt) caliper assembly be faulty?

Can you do me a favor and and jack the car up in the front and see if the wheel turns freely?

also when hot and locking on, crack the bleeder to see if it frees up, if so it will be a pressure retention problem, if not a mechanical issue.

I took the car to a tire store and while they were rotating my tries I was able to rotate all 4 tires. Tires rotated with some friction, seemed normal. Bearings had no play. The car was in neutral.
Last time when the brakes locked, I lifted the front and the tires would not rotate at all. Everything becomes normal after 30 to 45 minutes of cooling.
Some people suggested that I unscrew the brake line when the brakes lock to see if that releases the lock. To test this, do I unscrew the brake line at the MC or at the proportioning valve? Will it have the same effect if I open the bleeding screw at one of the front wheels? You mentioned there shouldn't be any pressure. Does it mean no brake fluid should drip out when I start unscrewing the brake line?
I haven't driven the car lately but I was able to use PB-blaster and safely unscrew the MC mounting bolt from the booster. The proportioning valve was attached to the bracket, so it moved as well. Some of suggested it could be a pushrod or pedal issue. I'll drive the car today or tomorrow and if it locks, I'll unbolt the MC and give it about 1/4 (quarter) inch slack for a minute and then bolt it back and report back to you guys.
BTW, I flushed the brake fluid and bled all four brakes yesterday. Existing fluid color was fine, not dark or rusty.
I'll keep you posted.

I flushed the brake fluid in April of 2017, used Prestone synthetic DOT3 brake fluid $8.99 each bottle. This synthetic brake fluid won't mix well with existing DOT3 fluid, it would create a separate layer when poured and then slowly mix, shining bright light will show separate blobs of liquid. Maybe that caused the brake locking issue.
I re-flushed the whole brake system day before yesterday and also rotated all 4 tires, loosened and hand tightened the master cylinder mounting bolts. I used Super Tech (Walmart) DOT3 brake fluid $1.89 a bottle this time. I drove around all day today but the wheel/brake wont lock again, the car is running fine for now. I'll update when the brake locks up again.

Please let us know what happens.

Cheers, Ken

I drove the car around for ~30 miles today, city traffic. Drove on the Interstate @ 70+ MPH for a short while. The brakes did not lock since the flush 2 days ago. The road/engine noise has been louder ever since early summer of this year when this issue started. I took temperatures of all wheels several times. Today and yesterday the front driver side lug nuts got warmer than the front passenger side - just opposite of the past experience - however, they were not hot, just warm.
I think it is too early to call this mystery solved, but it is pointing towards the unholy mix of synthetic and regular DOT3 fluid.
Will update again soon.

Sounds like you had Dot5 (Silicone) brake fluid in there. That is the only fluid that is not compatible with 3 and 4.

WRENCHTECH: I am 100% sure it was Prestone DOT3 fluid. I still have the yellow Prestone DOT3 synthetic brake fluid bottle with a little bit of fluid left on the shelf. I keep them in air-tight condition. If you like, I can take a photo of the bottle and post. Let me know.
Anyway, it is too early to say for sure that mixing the fluid was the underlying issue because this intermittent issue can still show up next month like it did before.

Yes if you can take a picture of the bottle it will help.

The photos of the Prestone synthetic DOT3 brake fluid are attached.
I have a new issue with pulsating grinding noise coming from underneath the car. I'll create a new post.

Yes, that is regular Dot 3. All dot 3 and 4 is synthetic. You may have had the silicone fluid in the to start with. That is the only thing that would have a compatibility issue

I have a 2005 Elantra with the same problem, the brakes start locking up after about 5 miles and I get a hard pedal. Leave it overnight and I can do the same thing over and over. First time it happened smoke was coming from the left front wheel so I replaced that caliper , next trip right front caliper had burning smell, I took that caliper apart and cleaned it, it did not stick but next drive brakes locked up so I went ahead and replaced right front caliper and both front brake lines. Still had same problem so I replaced the master cylinder, didn’t fix it, so I replaced the power booster and it didn’t fix it, next I replaced the power booster hose that has the internal check valve built in and the brakes still start locking up after 5 miles. I have put at least $800 in the brakes at this point, and FYI this car doesn’t have ABS. Any help would be greatly appreciated

Hello,

When the brakes are locked up jack the front of the car up then loosen the mounting bolts for the master 3 turns each to see if the wheel release. If so the push rod for the booster is too ling and need to be adjusted inwards. Also check the see if the brake pedal is returning fully. Can you please shoot a quick video with your phone so we can see what's going on, that would be great. You can upload it here with your response.