Brake problems

Hello all,
2006 Tacoma base, V6, auto, air, no other options, ~46,000 miles. I had a local mechanic replace the master cylinder twice: the first replacement was defective and replaced under warranty about 6 months ago. Ever since he replaced the master, the brake pedal had too much travel, going nearly to the floor, although the truck did stop. It felt like air in the system; I decided to bleed the brakes. I couldn't get any fluid out of the right rear bleed nipple. I jacked up the rear axle, put the truck in drive, and couldn't stop the rear wheels with the hydraulic brakes, only with the parking brake. So my question: is there any component of the braking system that can fail in such a way that no fluid gets to the rear brakes?
Hoodat

 

Typically, you hold the brake pedal down and start cracking the line open at each connection starting at the rear wheel cylinder working your way UP the the brake actuator.

 

Northern Idaho, 2006, 46,000 miles, I would not be surprised if moisture hadn't gotten into the wheel cylinder, rusted, and seized it. Many years of temperature changes will allow condensation to accumulate. Has the brake fluid ever been changed?

 

He said fluid will not come out of the bleeder.
The piston can be seized, and fluid will still come out the bleeder.
He either has a bad bleeder, or lack of pressure to the wheel cylinder.

 

Thanks all for your replies. The mechanic who replaced the two master cylinders replaced it again and thoroughly bled the system. They are all from the local NAPA store. The brakes work now, but there is still too much pedal travel for my liking. BTW, thanks TnShooter for the diagram showing the lines to and from the antilock mechanism. I'll need that if I have to do my own troubleshooting. Thinking along those lines (no pun intended), has anyone ever heard of an antilock system malfunctioning in a way that would block fluid to any wheel cylinders?
Hoodat

 

During the time period after the first mc replacement, brakes worked correctly? Is the brake pedal low AND mushy?

You could try bleeding with the engine running so you have the booster providing some extra power to push the fluid.

Another thing to try is both rear bleeders open, clear tubing attached to the bleeders and in a small container of brake fluid. Just enough fluid so the end of the tubing is submerged. What works good is a big roll of tape, a small container that fits in the hole. Keeps it from falling over. Then gently pump the pedal all the way down, all the way up repeatedly. You might see bubbles push out, then eventually no bubbles.

Here’s a theory. Local mechanic is probably not a dealership. He’s already stressed having to do warranty work and not being paid. He may have skipped over a few steps. Bench bleeding the new mc. Clearing air out of the abs properly.

I had the same happen which ended up being rust clogged brake lines.

I’m not sure why you didn’t bring it back to the same guy once you realized it isn’t right.

 

did he bleed the abs module? That is REQUIRED after an MC change and requires a higher end scanner that can perform it. A very common cause of long pedal travel is improperly adjusted drum brake. Must spin that star wheel on the adjuster until the shoes lightly drag. This often has to be done manually for several reasons

 

Waasheem: I did take it back to the same guy for all 3 master cylinders; the last two are on his dime.
Ir172: I didn't find any mention of bleeding the ABS module on the internet or in the manual. Do you have a reference to the procedure?
I put the rear axle on jack stands and put the transmission in drive at idle. A light touch on the brake pedal stopped the rear wheels. When spinning the rear wheels by hand I didn't notice by ear or feel the shoes just touching the drums. H-m-m; I use the parking brake enough that I expect the brakes to be adjusted properly. Will check further.
Again, thanks for the replies.
Hoodat

 

They have whats called self adjusters but, they don’t self adjust very good. They need to be manually adjusted occasionally. Adjusting until they slightly drag, then maybe back off a bit is what works for most everything. Our tacos need a specific procedure. Something like tightening until tight, then back off 15 clicks.

 

The abs module likes to trap air in the solenoids. It is possible to change an MC with very little air introduced if great care is taken. However, any air introduced at the MC will make it to the ABS module and is likely to get stuck there. The computerized abs bleed activates the abs solenoids and pushes the air out so it can be bled manually. This the case for most any modern vehicle.

 

Adjust the rear brakes:

 

The truck stops fine now; I put 240 lbs of sand in the back, headed down a steep paved street, and locked up at least the front wheels until the antilock kicked in. The pedal still travels further than I'd like, and the brakes don't 'pump up' on several pedal presses. Thanks, Jimmyh, for the illustration. I'll try that when it stops snowing.
Hoodat