4Hummer

Okay My Drivers side caliper isn't letting go. As in Im driving with my brakes on ALL the time. Some times it locks up so bad I can't move, I have been forced to pull over on the highway or road a couple times and Release the pressure via the bleeder valve.

Well Friday night I finally got around to replacing the caliper. I figured this was the problem as I had replace the passenger side last year. and this one is the original

So I replace the caliper, bleed the system and head back to part source with my old caliper to get my $60 buck back for the core charge. Hop back into the truck throw it in reverse and She wont budge.... Drivers side caliper is LOCKED again.

I go back into the store and ask buddy what else it could be... He says FLEX line. So I buy one $25.00 . release the pressure on the caliper and drive home.

This morning I replace the flex line, Bleed the system again. and Head to Toys R Us for some xmas shopping. AND GUESS WHAT ??? Yup it locked again


WHAT THE HECK could be the problem ???? All the lines are fine. the systems been bleed, New flex line, new caliper, Pads are fine (BUT Wearing quickly on one side) I seems to act up after I've been on the highway, more than city driving,


HELP PLEASE Im outta ideas.

tallboy

It kinda sounds like the check valve in the front side of the master cylinder is pluged or stuck. The reason only the one wheel is locking up is because in is the shortest line to the master cylinder. Being the caliper is not releasing the added friction would be heating the fluid causing it to expand and intern appling your brake on that side. The opposite side has a line running back to the porproting (spelling) valve making this side had more rom for heat expansion. Hope this helps.




Greg

Mad Chemist

How do you know its the driver's side caliper for sure? Did you jack the vehicle up and check all four tires? Is there a check valve somewhere in the line that is frozen up? What exactly is FLEX line?

89macrunner

it sounds to me like you need a new master cylinder...you can probably have your current one rebuilt or go to the dealer and buy a new one

superjoe83

next time it does it, break the line loose at the master cyl, and see if theres pressure there, if there is, then the master cyl is bad, but if not, then its farther down the line

4Hummer

I know its the drivers side Because A: thats where I feel it. B: that tires doesn't Spin when lifted off the ground, and C: I can see the pistons on that caliper are not releasing.

The Flex line is the rubber hose that goes in-between the Hard line from the master cylinder and the line just before the caliper.

4Hummer

Is there a way to test this check valve ? Can I remove it and clean it maybe ? Whats it look like and where is it ?

Sorry to sound so stupid but this problem has me stumped

tallboy

I know on the first gen master you could. On the newer models I dont know?
If you could on yours there will be a seat that could be unscrewed at the point wear the front brake line leaves the master cylinder. Remove the line and then unscrew the seat. Beware these parts are about the size of a Knats a$$ so it could be a loosing battle. Call your local parts store and see if they sell a rebuild kit. I hate brake problems. I think the check valve would come in the kit. Some one else also posted breaking the line at the master when the wheel locked up again. That would conferm that it is your master cylinder check valve. Happy hunting.



Greg

Ironmike4x4

Sounds most likely a check valve. I am not too sure on Toyotas but on GM vehicles we can take an air gauge and force air into the valve and see if its the problem. I dont know what to tell you on this one though.

waskillywabbit

iTrader: (-1)

Time to rebuild your MC as you got a bad valve there...from everything I read about MCs before I did my rear brake conversion.

Mikey

I wouldn't rebuild it. I'd just buy a reman unit. One thing I wouldn't do is mess with a master cylinder. Because if you get it wrong...........

TechWrench

There is another possibility, I have only seen it twice, but is can cause the problem you are having. If there is a clamp that holds the 'flex' brake line somewhere between the steel line and the caliper, and it has a rubber gromet, I have seen where the metal between the clamp and the gromet can rust and swell to the point that the hose gets pinched. If it gets pinched enough, it can act just like a check valve and not release all the pressure when the pedal is let go. Try loosening the clamp and see if the problem goes away.