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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 flushed the whole brake system yesterday (Dec 17, 2017) and 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 but the wheel/brake wont lock again, the car is running fine for now. I’ll update when the brake locks up again.Someone told me the valve on the photo with yellow question marks is a proportioning valve.
Some of you suggested that I unscrew the brake line when the brakes lock to see if that releases the lock. That will tell whether the MC is not taking back the fluid through the compensating port. 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?
BTW, I flushed the brake fluid and bled all four brakes yesterday. I’ll keep you posted.See the attached photo. My car has an extra valve bolted on the vacuum booster under the MC. The brake lines go from MC to that valve (highlighted in yellow question mark). Unscrewing the brake lines at the MC when wheels get locked may not release the brakes because of this extra valve. What is that extra valve and is it a check valve?
[hr]In the morning when I start the car everything sounds normal. When I start driving, after a few pumps on the brake, I hear loud dragging noise appear from underneath the car which goes away after a few miles. However, after driving for about 5 miles or so, I can feel the brakes locking and the drag becomes more obvious until the front wheels lock tight. Everything frees up after 45 minutes of cooling.
It is no longer an intermittent issue, the brakes lock every time. 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 or 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.
Which brake line (photo) should I loosen?[quote=”nightflyr” post=192265]The brake booster is vacuum driven.
……….being it happens intermittently in stop and go traffic does the feel of the brake pedal change? meaning does the pedal become extremely soft or hard?………….(1)
…………..Carry a wrench that fits the bleeders, drive the car and try to replicate the problem.
When it occurs, crack the bleeder open and see if it is applied line pressure causing the calipers to lock up………..(2) [/quote]
(1). When it happens, the brake pedal gets stuck in the up position, brake becomes super sensitive, the car drags and just touching the brake stops the car. Pressing the brake pedal with a lot of force wont make it 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 the pedal becomes normal.
(2). Could you please explain what to look for after opening the bleeder valve? Do I do it on all 4 wheels?[quote=”Evil-i” post=192279]My first guess would be a deteriorating flex hose at that wheel. Not relieving hydraulic pressure when you release the brake pedal.[/quote]
The flex hoses in the front are brand new. Front-driver whole caliper assembly with piston and gliding pins are brand new. Brake pads and shoes are new. Rear brake wheel cylinders are new. All tires are new. What else can be be causing this brake lockup issue?It does not have ABS.
Is there any way to test and eliminate some of the suspects you mentoned?
Someone mentioned brake booster / vacuum issue. What do you think?[quote=”Tods213″ post=192237]I’m glad the brakes are at least treating you better now. I’ve heard that the bearings usually go out in pairs on those cars. So that could be a thing. You could try a running test with the front tires off the ground and use an automotive stethoscope to pinpoint the noise. (Parking brake set, on level ground and use jack stands)
To rule out the tires, you could try rotating them and seeing if the noise changes.[/quote]
The mechanic who replaced the front-driver side bearing said the part looked fine and had no play. The other bearings have no play and seem to be fine. I’m thinking the bearings are probably not an issue. Any suggestion why the brake is locking?[quote=”Bonnieman” post=190927]Glad to hear the new hoses fixed the problem.
Thanks for reporting back.[/quote]
Problem still exists. Brakes locked up again. I added more details.[quote=”Tods213″ post=191961]I took a minute and read through both of those threads and I honestly think they’re both ending up in with the same conclusion I’m offering you.
Either way, lets say I’m wrong. Your options are wheel bearing replacement versus transmission replacement. Obviously, a tranny replacement is going to cost you a boat load more cash.
On top of that, we’re talking about a 17 year old Hyundai. Would you rather spend $2,000 on a tranny job (conservative estimate), or $400 on a front bearing job? At the end of the day, how much is this car worth to you?
I’m totally not trying to be rude with you brother. It’s just that the possible outcomes range from the kind of expensive to the prohibitively expensive.[/quote]
Please read my latest comments. I had a mechanic replace the front driver side wheel bearing. The droning noise is still there and only goes away when I am rotating steering to the right. Is it cheap tire or bad bearings on the rest of the car?
Since the replacement, I have driven the car only once and the brake/wheel did not get too hot and lock up since then. Which was an intermittent issue to begin with. The transmission worked fine. I’ll update again soon.Update #2.
I had a mechanic replace the front driver (F-D) side wheel bearing today. The rotor, hub, snap ring, ball joint etc. was solidly locked. I guess high heat caused the locking. Disassembly was a PITA job.
After replacing the F-D bearing I drove around with the mechanic.
The noise is still there. When I rotate the steering wheel to the right, the droning noise goes away and the noise remains in all other situations.
Someone from another forum suggested it could be cheap tire. My tires are brand new. The noise started a couple of weeks after buying these tires. I bought the cheapest Chinese tires available on sale from Discount Tire and they are notoriously troublesome according to some forums.
The wheel/brake locking issue has not happened since I had the F-D wheel bearing changed yesterday. Note that I only drove for 15 miles since replacing the F-D wheel bearing. I touched all 4 wheels after driving for 15 miles and they were all cold.
So, the droning noise is not related to F-D wheel bearing. It could be cheap tires or other bearings, right?
I will update again soon.I have 2 updates. Update #1.
The wheel or brake locked again 2 days ago. This time I took off the front driver side wheel because it was sizzling hot and the rest of the wheels were not even warm. It got that sizzling hot after driving for only 10 miles or so in city traffic. I lifted up the front wheels and tried to rotate the hub and rotor. They were solid locked and I got burnt through the gloves. Shoving a screw drive in between the rotor and brake pad easily freed the caliper assembly. So, the culprit was either the front passenger side brake or the wheel bearing. As many of you suggested, I’ll have a mechanic change the front driver side wheel bearing tomorrow.If it is highly expanding brake fluid that is locking the brake pedal, is it going over the boiling point and transforming the liquid into gas? When that happens,
if I simply open the the top of the brake fluid reservoir, wouldn’t it reduce the pressure? I did that and it did not make any difference. I live in Chicago. So, the overheating bad wheel bearing issue should be less likely to happen in the middle of freezing winter, is that a correct assumption?I appreciate your comment. I think it is logical to tackle the cheaper possible fix first. What is still a puzzle to me is the fact that the brake pedal got really hard and sensitive. Can you please explain to me how a bad wheel bearing can make the brake pedal very stiff and stuck on the up position?