Brake problem on 99 Tacoma V6, help if you can.

The rear adjusters can play a role in this problem. Whether or not they are playing a role is something you have to look at.

The adjustment of the rear brakes is what sets the pedal travel. Here's why, in a nutshell, the front brakes are disc, so they don't move very far and when you press on the pedal, the brake fluid exerts pressure on the pads very quickly but the rear brakes have to get to where they are going first.

The rear brakes have to span the distance from where they are at rest to where they press against the inside of the drums. This can be a very long way in terms of the brake pedal. The brake fluid pressure doesn't equalize until the rear shoes reach the drum.

There is a caveat to all of this, there is a check valve -- portioning valve is its real name. The job of this valve is to make sure, or try to make sure, that the system pressure is equalized from front to rear.

My first inclination was that you needed to bleed the system, it sounds like you have managed to get air in. Assuming you really did have the system flushed and bled - as you said - then I think you need to take a close look at the adjustment of the rear brakes. Personally, I have to wonder if the guys that flushed the system did it right because I think they should have adjusted the rear brakes as part of the service.

I don't recall if you said that the brake pedal holds steady at a traffic light, or that it sinks as you sit there waiting for the next Green. If it sinks, then you need a master cylinder.

Ok the rear brakes are set so there is not alot of travel but they are not rubbing either and the pedal is still soft and bottoms out. I will address the bleeding problem myself and see what I can get out of the system. You may be correct in saying that the guys at the shop did not know what they were doing. As for everything else the hoses look good and there are no leaks of any kind anywhere. I will be gone for a few days and will get back to update this then.

Thanks alot for your help,

Scott..

Rear adjusters will not cause a spongy pedal.

Incorrect information. Brake pedal is determined by the MC pushrod.

The valve is called a proportioning valve, not a portioning valve. The valve's job is not to make sure the pressure is equalized from front to rear - it is to make sure the proper proportion is delivered to the front and rear.

Rear brake adjustment or mis-adjustment is not causing the OP's problem.

You must be a pretty strong dude to carry the truck to a shop! Next time, carry it to a Toyota dealer. They would probably check the pushrod adjustment.

A spongy pedal is caused by air in the brake fluid. If you bled the system properly, (for LHD vehicles) starting with the right rear, then left rear, then right front, then left front wheel, and the pedal still feels spongy, then check for a fluid leak because air is getting into the system. More likely, the fluid was not properly bled.

Everything

That's not what it says in my repair manual. My manual clearly states that the rear brake adjustment can cause long pedal travel. Whether or not it is causing the trouble the OP is having is unknown, but setting the proper adjustment is the first step, or among one of any number of steps, that should be taken.

I agree that the MC pushrod is the actual part that determines pedal travel, but the rear brakes can play a role in the trouble if everything else is working properly.

Understood, but if it is problematic, it can be part of what the OP is complaining of.

I'm not sure tha tis correct. But if it is, it doesn't hurt to make sure the brake adjustments are set properly.

I don't know what repair manual you are referring to so you have me at a disadvantage but think about this...

New brake lining thickness is probably somewhere between 8 and 12 mm. Take a look at a ruler to get an idea of what 12 mm looks like. If properly installed brake shoes were never adjusted during its life, the most travel you could get is 8 to 12 mm, and I suspect that is what the manual is referring to by "long pedal travel."

The OP says that the pedal is going almost to the floor - that is a lot longer distance than 10 mm.

When rear drum brakes are out of adjustment, the complaint is usually poor braking performance or more rapid front brake wear, not long service brake pedal travel. You will get long parking brake pedal travel if the cable or shoes are out of adjustment.

A proportioning valve has nothing to do with brake pedal travel, whether it is problematic or not. A proportioning valve's function is to reduce rear wheel lockup. It is a disservice to tell the OP to check something that has nothing to do with brake pedal travel or pedal feel.

Yes, rear brakes should be properly adjusted and no, rear brake adjustment is not causing the OP's spongy brake pedal or movement almost all the way to the floor.

The OP said that the master cylinder was replaced and the rear shoes were adjusted and the problem went away for a while. Once rear brakes are adjusted, they don't suddenly get out of adjustment.

Upon re-reading the original post, the OP only mentioned that the spongy pedal returned and didn't mention whether the long pedal travel returned or not.

If a brake bleed only fixes things temporarily and then the spongy pedal returns, there is a leak in the system somewhere. Watch the brake fluid level in the reservoir. When looking for leaks, start behind the rubber boot and the wheel cylinders.

Well, I have never seen a brake lining that was 12mm, that's close to a half inch. The power of leverage can make the pedal move very far if the brake shoes don't hit anything.

Sorry if it sounded like his only problem is adjustment, I seriously doubt that adjustment is the only problem here. It could be one of the problems though, and observing the fix-the-cheapest-and-easiest-first rule, adjusting the rear brakes should be high on the list of things to cover.

This is true, for the most part. But long pedal travel can come from the back brakes taking a long time to get to the drums.

I agree that the parking brake will have a very long travel if the rear shoes are out of whack, and I do not recall if the OP mentioned this as a problem, or not.

I give.

As a long list of stuff to do, this is going to be at the very bottom. I was in error to have suggested it.

Yeah, I thought I read that too. I have to wonder if the shop bench bled the new master cylinder. If not, then there may be air trapped inside, and this will certainly give a spongy pedal.

I agree with that, Ray. I have to come back to the Bench Bleed for the new master cylinder. If the brakes are bled on the car, and become spongy again, then that tells me that there can be air trapped in the master cylinder itself. Logic says that the brakes should remain spongy even after normal bleeding, but I can recall doing my own brakes and having the pedal firm up for a few hours, then go soft again. Bench bleeding presses the plunger further than the brake pedal can, and this will drive out the last bit of air that can remain inside the MC. This air might not be evacuated by the brake pedal, but will influence the braking performance.

10 mm is a more typical lining thickness. The brake shoes will hit the drums, limiting pedal travel.

I do not subscribe to the fix the cheapest and easiest first rule unless I have no idea WTF is wrong and I'm taking shots in the dark. I subscribe to the "start with what usually causes the problem" and if unsuccessful, move to the "what can actually cause the problem" rule. I have had 100% success following these rules, working on hundreds of cars that dealership techs were having trouble fixing.

Yes, to a certain extent. There isn't enough room for the shoes to travel far enough to floor the brake pedal.

The OP didn't mention this and in my experience, didn't check it either. In either case, it is irrelevant info.

Many contributors to this forum like to suggest esoteric and obscure causes for problems, or causes they saw on other makes. Toyotas do not commonly have obscure and esoteric problems and because of how consistently they are made, a problem that occurs on one will likely appear on another under the same operating conditions.

Since a professional shop replaced the master cylinder, the odds are probably pretty fair that they did that procedure properly.

I think the OP and the OP's shop has missed a leak at a wheel cylinder or caliper. If it were me looking at the truck, I'd pull the rear drums and peel back the dust boot on the wheel cylinders to look for signs of moisture. Hint - I've seen this before.

Exactly, but if the adjuster is set poorly, then there can be several milimeters of travel before the brakes make contact, thena s the brakes wear the travel increases. I completely get that the rear brakes making contact limits pedal travel, that's why I said that this is something that needs to be looked at.

But Ray, we have no idea WTF the trouble is. The OP doesn't seem to have a clue either, so we have to start with the cheapest and easiest first rule if for no other reason than to get him to come back and say it worked or not.

No it not. If the parking brake pulls a mile before catching, or doesn't catch at all and the lever gets to the end, then the brake pedal will also go a very long way. Whether or not it can go to the floor is worthy of debate, but perhaps the OP is prone to exageration when he says the pedal goes to the carpets.

That is certainly a possibility, and one that I would have looked for long before I posted a question like this. I may have made a mistake to assume he would have looked here first but by the same token he should have looked at the adjustment of the brakes first too.

Since he had a new MC recently installed, I'm back to the Bench Bleeding, and the posibility that it wasn't done at all, or wasn't done right. I'd like to think they did the job right, but I'm running out of things to go wrong in such a relatively simple system.

You're missing the point here. First, the OP mentioned that the rear brakes were adjusted. Second, no matter how badly the rear brakes are adjusted, even if the shoe lining is gone, there isn't enough travel back there to make the pedal go to the floor. You will have long pedal travel and poor braking performance but the pedal will not go to the floor.

You may have no idea WTF the trouble is, I do.

The parking brake lever/pedal travel can be adjusted to account for shoe wear. You can have long parking brake lever/pedal travel where the parking brake does not engage and still have perfectly adjusted rear brakes.

Whether or not it can go to the floor is worthy of

Most people don't peel back the dust cover on the wheel cylinders unless there is an obvious leak.

You're right, I'm wrong.

All I know is that I had a car once that had very long pedal travel and the parking brake handle went to the limit of its travel. I adjusted the rear brakes and fixed everything.

Did the pedal go all the way to the floor?

If I was exagerating the facts to make a point, then yes, it went all of the way to the floor. Did it physically touch the carpets, no.

Figuratively, it went to the floor, literally it did not go to the floor.

Was the OP speaking literally or figuratively? I don't know for certain, so I took a guess.

I guess we differed in how we interpreted. When the Op said that the brake pedal goes to the floor and still can't lock up the tires, I took that as a literal description.

Yeah, I get it. I was thinking along the lines of stuff he can look at, and actually see something, before he went in for repairs to stuff he couldn't actually see. After a review of what he said, I'm thinking the MC is either defective, or was not properly bled on the bench before it was installed. I'd still double check the adjustment of the rear brakes as my starting point, then move on to issues of air in the system. Troubles with the MC will cause all of the symptoms he reported, whereas maladjusted rear brakes might only cause some of them, and there is the chance the adjustment will not play into his troubles at all.

I have to depart with you on the wheel cylinders though. My limited experience is that they leak to the outside if they are problematic, and are pretty obvious when they fail. They can cause his troubles, but a simple inspection of the brakes will show a leak if there is one. I have never had to peal back the covers on a wheel cylinder to see if it was bad, I knew it was bad as soon as the drum was clear of the lug bolts.

I think the original MC was bad and the replacement was not thoroughly bled when installed. The OP implied that the pedal is no longer going to the floor so at this point, another thorough bleeding would probably cure the problem.

Wheel cylinder failures are usually pretty obvious but I have seen some where the leak is not visible unless you peel back the dust boot.

Yes, I think this is probably where his repairs will take him.

That's why you get paid the big bucks ;-). I only see my own cars, but you do this crap all day long for a living so you will see the corner cases that get past me. I haven't seen a leaky wheel cylinder that didn't make a mess on the outside, but I generally don't see stuff until it has been broken for a while, wheras you might see things on the cusp of breaking while servicing other stuff that has already broken.

Given we are talking about a recent service call gone bad, then the wheel cylinders might require pulling the dust boots out of the way to look inside. This was a good call on your part, but probably not the problem.

Actually, I am no longer a factory rep, haven't been for 13 years, although I still work on friends' vehicles in addition to mine. I was on a trip with my college buddies and they could not believe that I drive a Lexus and still change the oil and do my own work. Part of the reason I do my own oil changes and work is that I can get it done at my convenience, although without the free car washes at the Lexus dealer.

The district service manager's job function is to oversee the service department operations at the dealerships in his or her district and not necessarily to fix problem cars. Dealer service personnel have technical hot lines they can contact if they have questions and field technical specialists and field service engineers can help out with really tricky problems so the DSM doesn't need a technical background. The service departments and their customers seem to prefer a DSM who can actually fix a car so they usually called me first. It is satisfying to be able to fix a problem car that even a master tech had problems with and fortunately, I only had to hand off 1 or 2 cars a year to the field technical specialist.

I once held an essentially equivelent position at Toshiba. I worked for the Electronic Imaging Division, our product set included copiers, facsimiles and printers. Different product set for sure, but essentially the same job. Similar rewards too, dealer technicians liked working with me because I came up from the trenches they still occupied.