Brakes locked up AGAIN!

Ok so tonight my brakes locked up on me again for the second time in two weeks. I was on the highway almost to workabout a 15min commute my steering wheel started to vibrate and would not stop at the same time I noticed my brake pedal was getting stiff. When I pulled over I didn't even have to apply the brake the truck just stopped. I had it in the shop last week for the same issue which they told me it was a bad master cylinder which they replaced and did a full flush. It lasted until now without a problem. Before I took it to the shop I had a bad wheel bearing replaced (front driver side) I was on the side of the road for about 30min with the truck off before the tow truck arrive at which time I started it back up to move it into a better position and the brakes worked again but the peddle was soft and spongey. I inspected what I could at night with a flash light and a buddy who checked the fluid which is clear and clean looking. He told me it might be a brake line collapsing. My truck just hit 92k its a 2wd auto with front discs and rear drums, ABS. Could a rotor be warped? The truck doesn't pull and rides straight and quiet at normal speeds I only noticed the wobble and brake issue as both times I was on the highway.I want to take it back to the shop and have them inspect it because we could not see anything obviously wrong.

 

brake booster might be a problem, but Id take it back to the shop you took it to

 

Yea def going to take it back. Is there anyway to inspect the booster or is it complicated?

 

You have to have someone help you but if you apply the brakes and you hear a hissing sound on the inside of the hood area by your brake booster is usually toasted. But it would be hard to stop unlike yours. I did however have an old ford that the brake booster went bad and it kept applying pressure to the brake master cylinder. There was no noise other than the brakes heating up and front end vibrating like you say yours does.

 

Yes thats what seems to be happening the brakes just apply themselves out of no where. The first time I barley made it down the highway before it happened and this time I was literally right near my job when it started to shake and lock up.

 

yeah my ford truck did the same thing...

 

did they flush your brake fluid? if not get that done. moisture can boil and cause expansion. that might cause the pedal pressure you describe.

 

Was it a independent repair shop or the dealer? There is an adjustment screw located under the master cylinder on the brake booster. The screw changes the distance between the master cylinder piston and the booster. Techs refer to it as "the do not fuck with screw". It's possible they adjusted it.

Did they change the master to stop a brake lock up? A master itself won't cause brakes to lock up. They may have changed it for a spongy brake pedal.

There's only a couple of thing that can cause brake lock up, a brake booster, contaminated brake fluid (oil), siezed brake calipers, a bad brake hose (fail internally and act as a one way valve (rare) and rear brakes contaminated with oil or out of adjustment (self energize).

The most common problems on Tacomas are the siezed caliper, leaking axles seals (contaminated shoes) and contaminated brake fluid. The others are very rare.

 

I still say you have a caliper piston locking up.

 

It was a local shop that replaced the master which fixed the issue for about a week. They flushed the fluid and installed new fluid which I checked its super clean. They said they did a complete flush and told me it was very dirty. It feels like just the front caliper and i want to even say the front passenger side. I had a buddy who use to be a mechanic tell me the same things you guys are. Its either bad break lines which he said are easy to replace or a locked up caliper. Is it possible to rebuild the caliper or is it better just to get new one from a parts store? I'm scheduled to have the shop inspect my truck first thing Monday morning.

 

Get two new rebuilt front calipers. Napa's a good choice.

 

Ok and I'm guessing replace the rubber brake lines as well since I'm down there?

 

I won't. Just do the calpiers and I'm sure it will be fine. Toyota brake hoses are rare to fail.

 

If my rotors are warped would it be obvious like once I install the new brakes and spin the wheel would I be able to hear it rub?

 

you will definitely feel it in the brake pedal.

 

Ok when my brakes worked before and after both lock ups the pedal felt fine. I'm just really bugged as to why it would just lock up out of no where, be fine after a flush and new master cylinder then lock up again the same exact way a week later after no issues.

 

Try jacking up one wheel at a time and see if it turns freely or if its having a hard time to even turn with the wheel off the ground. Our 4runner had all the calipers go bad and were dragging. The only thing I noticed was a drop in fuel mileage and some burned brake smell.

 

The out of nowhere leads me to believe a collapsed flex hose.

After the lockup, how long does it take to be able to drive it again?

 

After the first lock up I had my buddy replace the front passenger wheel bearing which I already had and was meaning to do and the wheel spun freely so did the other side. The truck has locked up three times no in total. The brakes will work after the truck sites. For example after the wheel bearing which we thought was the cause we drove around the neighborhood and it worked fine until two days later when I hit the highway for the first time it locked up after about 5min at 60mph. All times there was a brake smell but every time between that including before and after the bearing and new master installed at the shop I never noticed a smell. Last night I got the wobbles in the steering wheel pretty bad as I pulled over. For some reason one or both are just engaging on their own and not letting up. After they engage the pedal gets tight but still works like I can move a little and stop. I sat last night for about 30min waiting on a tow and when the tow arrived I hoped in my truck and the brake pedal was almost back to normal but super spongy and soft but still worked and applied the brakes. They just seem to close up as I'm driving and I didn't mash on my brakes on the highway either time it was in ligh traffic not stop and go.

 

After the lock up it takes about 20 or so minutes before its back to normal feeling.