Rear Brake Bleeding Problem

Hey all,

2007 V6 TRD Sport Tacoma

TLDR:Rear brakes won't bleed. Do I need a master cylinder or what else could it be and how do I confirm what the cause is.

I just replaced my brake drums, shoes, rotors, pads, and calipers. After replacing them I tried bleeding my brakes the old school method with a container a tube and someone manning the brake pedal. Though it is not what I should have done, I just bled passenger front the driver front since I figured there wouldn't be air in the rear. Bleeding seemed to work alright during the process (I've bled brakes on old vehicles multiple times always getting it to work well) but the brake pedal kept feeling spongy. Fluid will come out without air in the front and seem to be properly bled.

After taking the ego and wallet hit I decided to take it to a shop to let the "Professionals" do it right. Turns out my brake job was "perfect" according to them and I didn't mess up. They said they could not get the rear brakes to bled at all with any method (I know they did old school brake pedal and assuming either pressure or vacuum as the other thing they tried). They said the fronts were bled alright and could get the fronts to bleed but after 3 full flushes and inspecting all of my work etc. they concluded it must be a bad master cylinder and quoted me a bit over $$ $850 $$ to replace it including parts. Not doing that. Confirmation that the front brakes are good but the rears are not is that front lock up on dirt, rears don't.

Bleeds were tried with car on and car off. Car on was needed for fronts. It is a sport so I cant do the hold brake pedal to purge abs unit. More complications are that my abs does not work because my LF wheel speed sensor is dead and broke apart when trying to remove it (long story yes I tried with a screw to extract) and I do not have the time to rip apart the assembly to push out the plastic.

Do I replace the master cylinder? If so won't I most likely need my ABS unit working to purge the system? If so can I do a work around of a nice OBD reader or maybe if toyota has a program like ford to connect laptop to purge abs? Is it maybe just the proportioning valve and if that's built into the master cylinder is it just best to replace the whole cylinder? Could my rears be miss adjusted? They are right at the point they start to make noise but still spin and no hard spots at all in the pedal. Just spongy all the way to the floor. Also, why does the master cylinder have a plug going to it. What is that even controlling and could that have gone bad? Finding it very surprising for a master cylinder to just fail abruptly after a brake job.

Any help or knowledge is appreciated. Sorry for the long explanation. Let me know if any other info would be useful

 

I recently had an issue bleeding my rear brakes after a rebuild. I discovered the bleeder screws were stopped up with dirt and debri. Had to completely unscrew/remove them and clean them out with a small pic. Then reinstall.

 

Ok, lets see if we cant figure something out. When you apply your brakes, does your rear tires free spin? You may need to get the rear end up in the air on blocks and with the front wheels chalked, put the car in neutral then hold the brakes. If your rear tires still spin, are the rear drums properly adjusted? There's an adjustment screw hidden behind a rubber plug on the inner face of the drum. You'll turn it until you start to get a slight drag on the drums when you spin the tire then back it off one click. Your tires should resume free spinning at that point with no drag. Basically, the point behind this is we need to make sure that your brake actuates. You may not need to go all out on a new master cylinder. Check your rear brake cylinders to see if they are stuck. Pull the drums off and give a good spritzing with some brakleen and see what happens. You may be able to peel the boot back and see if it's corroded underneath.

-J

 

I'm following. I recently popped a line on the diff. Replaced it and can not get the pedal back. Bled many times.

 

I'll check out both those things tomorrow when I am off work and back in town with my truck. I assumed my wheel cylinders were fine because they looked good and weren't leaking and moved when I was putting shoes it but worth a check for sure. Thanks guys

 

They both stop from spinning if I press the brake. If parking brake (don't have someone to hold the brake at the moment) is on, same deal it stops but I can still spin it by hand if I put some force into it which parking brake on. There is a slight dragging sound already but it feels like the LR is catching more than the RR with the parking brake on.

 

Is there any way to check the master cylinder without getting air into the lines and is there any way to replace it without having to bleed the abs unit?

 

Alright, so since you say that the rear wheels stop spinning and the brakes are locked when you apply brake pedal pressure. This tells me that brake fluid is flowing through the lines and getting to the rear brake cylinders. Your parking brake is a mechanical hold via the parking brake cable. The next step in my troubleshooting process would be to remove the bleeder screws from the drum and see if they are clogged. As what @mikkydee suggested, I would remove the bleeder screws and check to see if they are clogged up with rust flakes. If there was any moisture in your brake lines it could potentially cause rust and that rust may have built up enough to block the bleeder screw when you cracked it. I would suggest picking up a set of speed bleeders and just replace what you have when you remove the old ones or another option would be to just clean and reinstall the old ones. To me, it sounds like the shop you took it to initially is trying to upsell you on some work that you don't need if your brakes are truly operating normally when you apply pressure to the brake pedal. If you decide to just get OEM brake bleeder screws, you'll be looking at an out the door prices of anywhere between $3 to $9. That's way better than the $800+ the shop was wanting to get from you. As a note, you will need to bleed your rear brakes after you crack the lines obviously so have some extra brake fluid on hand.

-J

 

Not sure on an 07 but my 09 the ABS pumps up the line pressure when you turn the key to on (and run) you hear the ABS pump run and stop you have line pressure.
Without the ABS pressurizing the rear lines nothing comes out. I put it all together then key to on (not running) and when the pump stops turn key off and then crack the bleeder and it easily bleeds.
Otherwise as stated check the bleed screws or just replace the wheel cylinders about $20 each at all stores.

 

@HasbroGamer I had this problem and I have a Sport as well. The shop that set up my gears undid the wheel cylinders when they pulled the axles and let my brake system bleed all the way out over night. They tried to tell my there's no way it did because the rubber stopper in the reservoir wouldn’t let air in. My ABS light was on. I drove it home without hardly any brakes. Found one rear wheel speed censor unplugged. Got it plugged back in then I used my Mighty Vac and pulled fluid until my hand would cramp then drove it slamming on the brakes making the ABS do its thing. I kept doing it until I got pressure at the rear bleeders. I would fix the speed sensor and try what I did before dropping $850 on a master cylinder. Sports are really finicky with their ABS Trac control bullshit. Or take it to the dealership and hook it up to Tech Stream and they can cycle it. It’s probably just a little air bubble trapped in your ABS module that needs to get worked out. It’s a royal pain in the ass to get working again. Side note if your Sport is a Manual bleed the slave too it shares the same reservoir as the brakes. Anyways good luck that’s my .02