Front Brakes are locking up!!!! Please Help!

[blombardo]

My Solution was a Master Cylinder

My Solution was a Master Cylinder -- 90 bucks at auto Zone. There are two holes in it - two lines that come out; apparently one of those holes were faulty. It's been over a week - about 500 miles and no problems. No more locking up.

Thanks for the information - I have learned a lot about braking systems.


Apparently if the ABS system was going to fail - A: my computer should say something or B: the brakes should pulse and not just lock up. If the ABS system was to fail the dealership told me I could choose to skip the $550.00 abs control module and instead simply install the $100.00 proportioning valve (which would in effect downgrade my vehicles braking system but it would still function safely)

I'm curious to know what the OP's solution was.
-Brian

 

[Awz]

I'd check the brake pedal pivot bolt. When I worked for Saturn, I had a 2009 VUE come in for nearly the same problem. I through some parts at it (after calling the technician support and stumping even them) It took almost a week but I finally found a position where, applying the pedal slowly, I could feel it apply itself more, and lock the front brakes. Sadly on this one simply loosening the bolt didn't work. Had to replace the pedal which required the removal of the ENTIRE dash up to the firewall. Took me two days

Mike

 

[cstmp8r]

I have the same exact problem with my 90. Drives fine for about 10-15 miles then slowly pressurizes and locks the front wheels. I replaced the mc and the booster and it was fine for a few days then started again. Everyone I have talked to has no idea what it could be. Also, when it first started it would lock while running but as soon as I turned the motor off it would release and roll fine. But once I started the motor again it would instantly lock up again. If I let it sit for a half an hour or so it would be fine again until I drove another 10-15 miles. One of the most frustrating troublshooting ever! I was thrilled to see another person with the same problem until I saw no remedy..lol..

 

[dengay1958]

Possible solution!!!!!

I have a '91 (Gen 2) Toyota 4x4 extended cab with 251K on it that was doing the EXACT same thing! I replaced both calipers and the master cylinder but the front brakes would still lock up occasionally.

After thinking it over, I knew it had to be a vacuum or other such problem that was causing pressure to build and not release. By chance, I pulled the cap off of the master cylinder and removed the low fluid switch and what I found really set a lightbulb off in my head!!

A piece of the epoxy (?) used to glue the wires for the low fluid indicator, about the size of my little fingernail, had broken off, probably due to contact with brake fluid over the years, and was lodged in the top of the cap right where the breather hole is. It was apparently being sucked up and blocked the breather hole allowing the system to build pressure but not release it until the engine was shut off which in turn released the vacuum and allowed it to fall away from the hole.

I cannot be 100% certain this was the issue, but I removed that piece 5 days ago and the brakes have not locked up once since. :amen:

Pull the master cylinder cap and then the low fluid switch and see what you find!!