Rear brakes won't enage

Hey, hope someone out there has an idea on my issue, I'm stumped and the mechanics working on my truck are at a dead end too. Here's my problem

I've got a 1998 Tacoma, Limited, 4x4, and my rear brakes will not engage. They're not slow, they will not engage at all, and my emergency brake is the same way. There was a bad axle seal that was replaced along with a bad bearing(and all the brake components except the drums because they disintegrated after the fluid was pushed in on them, they were new before), the fuse for the ABS was replaced to see if that was the problem, the regulator is good, and the front brakes are engaging just fine.

The mechanics working on my truck now are also looking for possible answers online, I thought I'd try asking here as I've found answers before.

Any ideas as to what might get them working again?

 

They must be so far out of adjustment, that the shoes can't come in contact with the drum.
When you pull on the e-brake handle, do the bell-cranks move (back side of rear brake backing plate)?

 

from what you say, you probably need new drums. they just might be oversized/overcut or just too polished. your e-brake should only click 3 or 4 times when setting. if not, its another indication your drums are oversized. this is all assuming the shoes and hardware are all new. unless they didn't properly adjust your brakes after putting on your new shoes at all.

If you wan't, you can also have your lines bled. It doesn't usually cause this kind of issue, but if the brake fluid is old, why not change it as a preventative measure? maybe there's a little air in the system or your wheel cylinders causing this issue.

then again, if your wheel cylinders are shot/siezed. they may also cause this problem since the proportioning valve is supposed to make sure your rear shoes are engaged before the front pads. if they're locked/siezed, it will be as though they are engaging when not. press on your brakes REALLY hard to see what happens.

try to do an adjustment first though. if you press too hard and your shoes aren't adjusted properly, you may pop the pistons out of the cylinders causing brake fluid to go everywhere and needing new shoes, fluid, and a headache of stuff.

 

ABS module bleeding procedure?
Wheel cylinders seized?

BTW brake fluid should be changed every two years. Brake fluid is hygroscopic and absorbs water from the air (through the breather in your master cyl and even while you open a can and pour it in) and the water in your brake fluid will boil (no brakes) when it gets to, you guess it with me...212 F. Not to mention rusting everything inside that made of iron.

 

I really have to wonder What kind of mechanics can not have figured this out.

Comes down to either hydraulic or mechanical.

One would bleed the brakes if your even getting fluid to the rear cylinders

ABS valves do fail!!

Mechanical things just are not adjusted up as your Emergency brake does not work.

While things were apart why did you just not replace the drums ?? They were at least measured ???

 

Make sure the LSPV (the thing on the driver's side frame rail that has a rod that comes down to the axle) is working correctly. It has a bleeding procedure of its own as it is a high point in the rear breaking system. Sometimes it can leak and who knows it may have gone stuck and be bleeding your pressure to the return line. I would check the wheel cylinders for leaking or completely blown seals and make sure you have had the break shoes properly preloaded and adjusted so they can contact the drum surface. Good luck

 

oh yeah I forgot about the load sensing proportioning valve on the 1 gen. Bend the rod or do suspension work and it's all kattawampus.

 

I'll pass these suggestions on to the people working on my truck now, see if there is anything they haven't hit yet.

My drums are brand new, I replaced the drums and all the hardware inside(though the shoes had to be replaced again because they fell apart after the fluid blew out into them again). The odd thing with adjusting them, when I helped my dad anyway, is that he got them adjusted and the lines bled out so that, at least when the truck was off everything back there was moving in response to pedal and emergency brake. But when it was running it went very quickly from barely working to not engaging period. We've been having this issue for a long while, I had to park my truck for several months because it became too unsafe to drive.

Update:
I talked to the mechanics, and they have been through everything suggested here so far, still with nothing getting the brakes to work. They had adjusted the LSPV and it had a minimal effect, not enough to really make a difference. As for pressing really hard on the brakes, he just did that last night with the truck on grass, and still the back tires won't stop turning.

 

Were the tires elevated? If you lift the frame and leave the tires hanging, the lspv will almost fully disengage, if i remember correctly. lift the truck from the axle when checking the brakes.

 

They've done it with the rear end up, truck running, and the tires off, and also with the truck actually moving on the ground, no difference either way. They had the rear end supported on jacks, rather than lifting the entire truck.

 

I see that the shoes were replaced, but not the drums.
Have they checked for mis-matching shoes (ie - intended for a drum of a different diameter) ?

It could happen. Years ago, on my '84 4runner, I replaced the complete rear brake assemblies, including backing plate, with ones from an '87 model that had larger drums, for better braking. When I sold it, I made sure to tell the buyer about it, so that if he ever replaces the shoes he would get ones for an '87 truck, not an '84.

 

The drums are new as well, though they were put on several months back, there is no wear because the brakes won't grab. The shoes had to be replaced again because the fluid that blew out onto them made them fall apart. The seal that caused that has been replaced now

 

Your next step is to go from the brake booster to the rear splitter then to the cylinders removing brake line and blowing compressed air until you zero in on the problem.

 

Well, the brakes are working now. Changing the master cylinder got partial functionality back, the rest came back with bypassing the ABS. The rear tires will now lock up when they need to, so I can drive my truck again! Which is great because I love my beetle, but it's getting cold and my truck has a better heater. Thanks everyone that came and gave suggestions.

 

Curious how you bypassed that useless system that is the ABS??

 

I would think long and hard about a shop unable to figure this out .

Not hard to eliminate the ABS Computer/valve just some new brake lines.

 

I'm personally not sure how to bypass, my dad had been considering doing it though, had they not. I'm not a mechanic myself, I know how to do maintenance, but that's about it myself.

They weren't the only ones that had issue, there were quite a few people before then that couldn't figure it out. The first place went so far as to tell me my brakes were fine and I just didn't know how to drive. I'm happy with them, they've always treated me fairly and doesn't a lot of time untangling my bug, which is why I sent my truck as well.

 

A few years back, I had to replace the master cylinder in my S-10 Blazer that had ABS. Tried every which way to bleed the system and get the pedal back up to a normal height. The brakes worked but the pedal went nearly to the floor. Even rented a power bleeder that used air pressure to get the air out of the system, and it didn't improve things either.
Went to a wrecking yard, driving another vehicle, and found and priced another ABS module as I figured that was my problem. Decided to drive the S-10 to the wrecking yard to pull and buy the ABS from the donor vehicle. That way I could compare both units make sure I was getting the exact same thing.
Anyway, the wrecking yard had a gravel parking lot and I pulled up a little to quick and had to slam on the brakes, the rear wheels skidded and while doing so the ABS unit started running and pumped up the brake pedal to normal height in seconds. It was fixed!!!!!! This is a true story. And I saved the $50 they wanted for the used unit. I had talked to lots of people about my problem and no one suggested I go find some loose gravel, slam on the brakes and let the ABS unit do it thing.

 

that reminds me I seem to recall hearing about some vehicle's bleeding procedure included jumping the abs motor to do the very same thing. Can't remember where I heard that or what car it was for.