Brakes locked up AGAIN!

Is the wheel on the offending side filled with more dust than the other side (front discs) Doesn't have to be on the outside of the wheel, could be the inside.

This is an indicator of a engaged caliper. It's possible it is partially engaged, runs enough to build a lot of heat, swells enough to lock the caliper. At that point you are almost boiling fluid.

You should find one or both of the pads on the offending side much more worn than the other side. Or maybe the inside pad worn a lot, and the outside pad just a bit.

You may have a broken pad shifting around and doing naughty things.

BTW, get the warped rotor idea out of your head. http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

There has to be some indicator of the problem.

I've never seen a master (which was replaced) lock up brakes, only cause 'no brakes/low brakes'. I've never seen a booster cause lock up brakes, only a very stiff pedal (manual brakes, no power assist)

I agree with @Jimmyh, the caliper(s) are the prime suspect.

Please keep us up on the final verdict. I would have won money if I'd bet you'd be back with the same problem after the master replacement...........

 

I will check the pads for wear and cracks. I keep my rims clean and the first time it locked up it appeared the front passenger had some dust on it more so then the driver side but again it was just a minor amount. The out of no where thing is really bothering me because there is no pulling to one side, smell or noise so I'm super nervous every time I drive and last night sucked it was fine for a week after the shops wrong fix.

 

Ok took it back to the shop they tell me its a bad booster, the booster is a Toyota only part and the total with labor will be $1,300. They said they can save $200 by reusing the existing lines. Please help with advice. Thanks

 

Did a quick check on Rockauto.com and they list about 5 boosters for a 2007 Tacoma, but they are all "Out of Stock" Still, I find it hard to believe it's a Dealer Only item.

 

I see stores like O'Rileys and Advanced carry it and can order it for way less.

 

The booster is easy to test. If you want to do it yourself, find where the vacuum hose goes into the booster. The next time your brakes lock up, pull over and disconnect that vacuum hose. If the brakes free up, bingo – you need a booster.

Not sure what 'lines' they are talking about. And while a bad booster can stay in 'boost mode' keeping the brakes engaged after you release the pedal, I don't know how it could engage the brakes just rolling down the road from your description.

If you do verify it's the booster, and it truly is a dealer only look for a junkyard part. Or shop that rebuilds them.

If you can't satisfy yourself with the test I mention above, at least get a second opinion. There's a lot of $ on the line to be wrong.

BTW, it's not something that's hard to change. No reason not to have a DIY day on this.

 

I found some boosters aftermarket at AutoZone for around $250. The mechanic who test drove my car just called back and said he drove it on the highway and felt the brakes start to lock at which point he pulled over and did what you mentioned above he removed the hose and they free'd up he said he repeated this a few times but wants to see if its the brake flex lines which he offered to install and test out for $60. My mechanic friend told me if it is the booster he will install it for me.

 

While I usually don't like to troubleshoot by substitution, you're around 10 yrs on those flex hoses and I bet they're original. I reckon for $60 that's not a bad idea either way.

 

Well if these $60 hoses don't work I'll be taking the truck home. The mechanic mentioned the only way the booster would apply the brakes on its own is if it builds vacuum where it shouldn't and when they locked up on him they released as soon as he removed the vacuum line from the booster. Would the booster make a noise if it had a punctured diaphragm inside of it? I just hate not knowing whats wrong when my daily commute has me on the highway.

 

Has anyone ever heard of a brake booster building vacuum in a part it shouldn't and apply the brakes?

 

Remember I mentioned the "do not fuck with" screw. I bet you someone made an adjustment when they had the master cylinder off. It's rare to see a Toyota brake booster with problems.

 

This has been super frustrating and confusing. I will post any new updates but appreciate the help and advice on here. I'm having new brake flex lines installed hoping maybe one collapsed. I will keep post any updates or changes. I swear if its not one thing its another.

 

http://www.rockauto.com/en/catalog/...4686,brake/wheel+hub,power+brake+booster,1884

 

Ok new master, new hoses and still no fix. The brakes lock up on highway drives not city streets. When they do lock up they release after removing the vacuum line from the booster OR letting it sit for about 30min.

 

The next time your brakes lock up, pull over and disconnect that vacuum hose. If the brakes free up, bingo – you need a booster.

Removing the vacuum frees the brakes up. I wonder if it only happens on highway drives because its building a vacuum where it shouldn't?

 

Be sure the brake pedal pushrod is not adjusted too long.

 

I guess I missed that.

 

There is an adjustment screw under the master cylinder on the brake booster. Make sure that screw is adjusted to the correct length. When they put the masterm cylinder on and if the tech made an adjustment you could have the exact problem your experiencing.

Toyota brake booster failure rate is very low.

 

This first happened to me weeks ago leaving work. My truck still had the OEM master cylinder and no brake systems arriving to work but when I went to leave the brake pedal was really sensitive like the slightest pressure applied the brakes. I made it about 1/2 mile before the steering wheel began to shake and my truck began to slow down due to the front brakes applying by themselves. Today my mechanic tried to replicate the problem and couldn't until he drove on the highway. He said they began to lock up twice and both times he pulled over, removed the vacuum line from the booster and the brakes released.

 

http://www.customtacos.com/tech.old...6toyrm/06toypdf/06rmsrc/rm2006ta/04200610.pdf

http://www.customtacos.com/tech.old...6toyrm/06toypdf/06rmsrc/rm2006ta/04200410.pdf