Brakes locked up AGAIN!

Check the screw and if it's within spec change the booster.

 

Thanks.

 

Awesome and thank god I do not have the VSC

 

Any write up's you know of on checking this screw and knowing how its suppose to be adjusted? I doubt it is this because the OEM MC was never touched since I owned the vehicle and this locking up happened out of no where.

 

One thing that can cause this is a dragging brake. My son had a mustang that did this thanks to a caliper pin that was grundgy. If the thing drags, it gets hot, and brake fluid WILL boil if you get it hot enough, and when it boils it produces pressure that will keep the brake engaged. But you should be able to smell it. We jacked his mustang up to figure out which wheel. After you let it sit, the fluid cools off, and the pressure is released.

Whether that is your problem or not is unknown without having hands on the truck. If it happens again, CAREFULLY touch each wheel in the center. If you have this problem you will know it instantly as the hub will be HOT...

 

I touched each wheel after it locked up twice and nothing was hot to the touch but I def smelled burnt brake smell but didn't notice any excess dust on my rims. I replaced a bad wheel bearing, master cylinder and brake flex lines. The brakes don't drag on city streets and there is no brake smell. On the highway I made it a week after replacing the master cylinder will a full flush before they locked up one night on the highway which causes a violent wheel shake. They released after I was parked for about 30min but had it towed home anyways. My mechanic test drove it today without issue until he took it on the highway where he claims it locked up on him twice and both times he removed the vacuum line on the booster which freed up the brakes. It has to be either the booster, check valve, or stuck caliper. When we replaced the bearing the pads were still meaty and appeared to worn pretty evenly.

 

You should be able to find it in the service manual. Just want to confirm before changing the booster. You could also compare the adjustment to the new booster. If the screw adjustment is the same proceed with changing out the booster.

 

Ok thanks! This is so frustrating!

 

Just weird that it did the same thing with the OEM MC and the aftermarket MC

 

I had the same thing, it was a brake caliper. Changed both since they were originals w/235k miles on them. Then did a brake fluid flush/refill. Brake system gets water in it over time when you open it. Rusts the pistons, journals. The master is see-through so you don't have to open it to check the level, for this very reason.

 

Seems to me that if it did the same thing with both master cylinders that would indicate your problem was not with the master cylinder to begin with. Wouldn't be the first time a problem was misdiagnosed.

 

Yea I feel sick to my stomach for jumping the gun and just taking it to a shop instead of waiting for suggestions on here. So now I have a new master cylinder along with new flex lines for both front calipers. I'm going to test the booster myself for vacuum using the pedal test because the mechanic said when it locked up on him he disconnected the vacuum line which released the brakes so if I'm not mistaken thats a bad booster.

 

What were your symptoms? My brags don't stick or drag they just apply out of no where on the highway. They are find on city streets and no brake dust build up on my rims. I never mashed on my brakes either on the highway they just locked up three different times all at different distances from my house.

 

Any updates?

 

Not trying to be a smart ass but you really haven't followed the advice some of us have given you. I said to you don't change the brake hoses or MC, these parts are rare to fail and you went ahead and did it anyways.

Personally I think you should bring it in to a different shop. One that is trustworthy and honest. Trying to diagnose via a forum with limited skills can end up costing more than if you brought it into a shop.

 

Not being a smart ass at all I'm a dumb ass and ignored good advice. Being I have a new MC, brake flex lines and it still locks up randomly on the highway and only releases when the vacuum line is removed from the booster or the truck is let to sit for about 20min. I have a trustworthy friend who is a former service tech, he is going to install a replacement booster for me. Sorry I did not listen to you all and acted irrationally it has really been bugging me. I will update after the issue is resolved and hopefully have some good advice for any future issues anyone else may have like this.

 

Had a family mechanic check my calipers after the advice and he said they are fine. Just got in my truck and my brake pedal is hard to push feels like a rock. It wont leave park until I start it and then the brakes are sensitive. They will lock up if I drive long enough and only release when I remove the vacuum hose off the booster itself. I can't seem to find a booster at any parts store I can order. I was just fucked over by O'Reilly's who ordered one last week and waited until today to tell me it was an inventory error and they cannot get one. I found one on Discount Auto site and Ebay I need help with a part #. I have a 07 Pre Runner 2wd no stability control. I found a booster online which says it will fit my model part #53-4925. Has anybody ordered a booster online and not from Toyota? SHould I grab one off ebay or Amazon? Local parts stores have it on their sites but say they do not have it in their warehouse.

 

Welp, that part number seems to check out as far as compatibility.

http://www.oreillyauto.com/site/c/d...34685_-1&pt=01305&ppt=C0066#compatibilityTab_

 

You need to verify the adjustment screw under the master cylinder on the brake booster before you buy a booster.

http://www.doityourself.com/stry/how-to-perform-a-brake-booster-push-rod-adjustment

 

Thank you! Will post update afterwords. Does it matter that this problem happened out of nowhere nothing was tampered with the pedal was just stiff as a board one night as I left work?