911...brake gurus needed!

Searched, some similar but no definitive answers. 2009 Tacoma DCSB 4x4, changed the front pads and rotors yesterday. Pads and rotors are installed correctly, break in performed accurately.

My issue is there is no firmness in the pedal whatsoever now on the first pump. The second pump will stop on a dime. I have reversed bled, gravity bled, master cylinder bled and the old pump and hold routine as well. No discernible air in the lines at all.

After reading a few threads, I went to a gravel road and forced the ABS to kick in about 4 or 5 times, then bled the system again. No change, pedal is still to the floor on the initial depress.

Any ideas? Should I just change the master cylinder as well? Wheel cylinders are fine, no fluid loss thru the system, pedal feels as if air is in it but none to be found no matter the bleeding process. This is my work vehicle (I actually work out of it) and had to take the day off because this needs fixed. Anyone out there that can save me? Thanks in advance.

 

How are the rears? Are they adjusted properly?

 

Tell us how you moved the pistons back into the calipers.

 

Sounds like a master with an internal bypassing failure. Could have been on the cusp of failure and the bleeding process pushed it over the edge.

Had that happen on an old Z car once, took me a few hours of struggle to figure out what was happening.

Be sure to bench bleed the new master!

 

make sure the rears are adjusted properly. Sounds like you are having to fill up the rear cylinders with the first pump then it finally gets firm.

 

brake booster? usually if your master is shot then your pedal will be spongy not completely useless

 

I c-clamped the pistons back with the lid off the master cylinder. Checked the rears this morning first thing, everything looks good. Self adjuster still works like a top and get a slight , very slight rubbing sound when free spinning the rear drums.

The second pump feels like the brakes on a Ferrari (well for a Tacoma anyways) but the first depress has nothing, it will eventually stop you at the bottom of the pedal but that isnt really confidence inspiring with the drivers in the South. I am thinking of just going to get a master cylinder but 165 dollars is a lot to drop on OEM if that doesnt solve the problem.



BTW, truck has 103k on it. Front pads looked fine when changing but I am doing all the general maintenance so that for piece of mind I know when it was done. First time I have ever had an issue with this and it is perplexing to say the least.

 

Did you clean and lube the caliper bolts? Sounds like a bad master cylinder.

 

Yes, brake cleaner on all pins and bolts. Sanded the pins and lubricated everyth ing. The front brakes work fine when engaged, no grinding squealing or clunking. The emergency brake is tight and feeling right. I am just going to assume its the master cylinder , as said above it may be suffering from blow by. The booster seems fine as the pedal with the truck off holds firm for the 2 minutes or so that I kept pressure on it.

 

Why would the master cylinder or the brake booster fail though?

What fluid did you use and how much? I'll go out on a limb...if you used that commonly available 1L Valvoline synthetic container, it's probably not as good as Toyota'a brake fluid (I've used Valvoline synthetic several times on other vehicles and was never satisfied- actually had same issue you are describing). Generic fluid certainly isnt recommend either. Also, brake fluid must all be used once that container seal is removed...it can't be stored for later use once opened.

Sounds like to me you may still have air in the lines. ( had same issue ( brake firmness not achieved until 2 or more brake applications) on my old Mazda until I bled the brakes with speed bleeders).

 

You compressed the caliper pistons with the bleeder open or closed ?

 

Closed, lid off the master.

 

I vote for air in the lines. I know you bleed the brakes multiple ways but some air is still there.

I don't think it's the master. If it was bleeding by the brake pedal would be good at first and then slowly go to the floor.

 

possible,

I never had an issue with using clamps to return the pistons back. Meaning I never had to bleed them after doing new pads. Did you do the bleed in the correct order? Other than that it could be the master cylinder is on its final legs and going out.

 

Bled from RR,LR,RF,LF.

 

It's hard to imagine you still have air in the lines. So i'd bet there is slack to take up in the system. Maybe one of the pistons is stuck or the rears need to be tighter.

 

What is the definitive way to check for a stuck caliper? Pull the wheel and watch as the pedal is depressed?


After install and before putting tires back on, pads looked seated properly and there is no odd sound happening during braking.

 

When you pushed the caliper pistons back, you forced all the crappy old brake fluid up through the ABS unit, that may be part/all of your problem. ALWAYS open up the bleeders before collapsing the caliper pistons, that way the fluid doesn't get force back through the system.

 

That should work.

 

basically this, have someone help you. Apply the brakes and if the pad is loose when applying the brakes you have a stuck piston. but I would think it would pull to one side or the other if this was the case.