HELP! No brake ideas left...

[handle with care..]

Hi! I've opened this account for this express reason. We are at a loss with our 99 4runner. We've been working on it for 5 months now!

History:
On Christmas eve, while it was snowing, the brake pedal suddenly got rock hard halfway to our destination. We were impressed as we always thought it was too squishy. Three days later we went to brake and suddenly the pedal went to the floor with very little brakes. We found out the the rear passenger brake cylinder had exploded. We replaced the brake cylinder and cleaned area. Replaced pads at the same time. The pressure never returned to the brake pedal. It's gone to the floor ever since with varying degrees of resistance (nothing exceptable though), throughout all our time "fixing". We've yet to figure out the problem. It's scary to drive, as it doesn't stop until the last second (and pedal always has to be to the floor). Since then, we have replaced the brake lines, rebuilt front brakes, new: pads, roters, 3 new master cylinders (all bench bled first) as everyone kept saying that was the problem, new brake booster, have re calibrated plunger and pedal, performed more pressurized bleedings than we can count, performed manual bleeds for good measure, a system flush, bleed ABS system, and cannot find any leaks anywhere! We've used every trick and suggestion for bleeding the brakes that can be found on the internet: pressurized, 2 person, 3 person, abs bleed, MC bleed, etc.

Where we stand now:

When the vehicle is off, we can pump brakes and they get hard within 3-6 pumps. As soon as the vehicle is turned on, the pedal goes straight to the floor. It is stopping but it's scary. There is no pressure behind the pedal at all. Now last week the ABS light just came on and the garage has said they can't read it because 99's don't record "codes" for ABS. We don't know if they are connected or not, but the ABS system is still ratcheting/engaging when you start the vehicle, as well as when roads are slick (tried it in the rain last week). Fuses appear to be good (as in nothing is black, but I don't know much about them so I could be wrong...), (getting desperate here).
We need this vehicle and my wife and young son use this vehicle, so we really need to get it safe!

I'm out of ideas, but really cannot afford toyota's prices to diagnose! (Job is in limbo at the moment.)

HELP!!!

 

[Singtoe]

You might have a bad abs pump. Its the only thing that you haven't messed with.

I think, when you lost the rear cylinder, The abs pumps proportion part collapsed and letting it not build up pressure.

 

[Drcoffee]

How does the brake pedal feel when you pull the the ABS fuse? You may have a bad ABS system. Its a simple system in its function. If its not leaking and all the pads are new the fluid is either not getting presurized (bad master or air in the line) or its being absorbed by the ABS system.

 

[handle with care..]

Will have to try that. I haven't messed with the fuses because I don't know much about them.

How should it feel once the fuse is pulled? How will I know if the system is good or bad?

 

[Drcoffee]

If the ABS is deactivatted it may let the brakes function normally. Its worth a try. Singte may be right and there could be a internal failure of he ABS. you can find the abs fuse under the hood.

 

[BlackCat914]

I'd agree with the above, and I'd also look into making sure the shoes are adjusted properly. Drum brakes have a huge impact on pedal height.

 

[nissanh]

Do you use the park brake at all?

Toyota park brake basically adjust the rear brake shoes every time you pull it.

Then try the front wheel bearing free play. I once went through hell with the brakes.
While the car is parked, hold the 12'o' clock position and push it in and out. If you feel any movement that may be the cause. Free movement moves the rotor, hence pistons in the caliper.

How about the flexible hoses? How old are they?

 

[handle with care..]

Alright. Got fuse pulled out. Test drove it. No change. Does that mean the ABS system is alright or bad? Got a new abs pump on the way just to be safe on that aspect... Will let you know about that then when it's in...

 

[Singtoe]

When the ABS light is on. It is the defacto same as pulling the fuse. So there should be no change in operation.

 

[Drcoffee]

Have someone start the engine and pump the brakes. Crawl under the truck and look at the rubber flex lines to see if they are buldging when the brakes are applied. There is also a flex line over the differential.

 

[handle with care..]

Alright. We replaced the ABS pump now too. Bled a ton of air off of it, with pressure bleeder. Put abs fuse back in, and reconnected battery.

No change in brakes and ABS light is still on. Any other ideas?

I noticed that with car on and in park, I can pump brakes 4 times now and they are stiff but if I just sit with and hold my foot on the brake after the 4th pump, it will start to slowly go down again.

On another topic, ABS is no longer ratcheting when the car is first put into gear after starting it either... Used to hear the crunch sound when I first put it in gear after starting. Now I don't.

 

[Drcoffee]

I think its time to take it the dealership.

 

[Singtoe]

If it not leaking anywhere and your brake pedal is bleeding down, your MC is bad.

Now, you said that you have replaced it 3 times all ready?



Get a new MC from someone else.

 

[handle with care..]

First one came from toyota. Next two came from rockauto.com.

 

[LittleCaesar]

I would agree that it sounds like a bad MC, but unless you have a stripped flare fitting at the MC, I would think that at least one of the MCs was good and would have worked for you.

I'd say maybe there is a small leak somewhere in the hard line, but that is the luxury I have. When bleeding, is there a steady stream of bubbles at any of the cylinders/calipers?

I remember reading a post some time back where a guy had lost pressure while on a trip, pedal to the floor mimicking a bad MC where in fact both front brake lines had internally collapsed. I take it you replaced all three?

As Dr. Coffee said, take it to the stealership rather than just throwing more money at it.

 

[handle with care..]

a partial update...

Took it to the garage...

Said abs light was throwing 2 codes. First, left front speed sensor was not working. Second was a break in the circuit (said he wouldn't be able to know about that one until the sensor was replaced because the second may have been caused by the fuse being removed and put back in...).

Then he informs me that if he was I, he'd be more concerned about trying to get the breaks fixed first. :frusty: Sigh*

Recieved a few more suggestions. Will try those and then it's off to Toyota if it doesn't work.

 

[handle with care..]

welcome. I'll keep updating in hopes of helping someone else who goes through this...

 

[Brian757]

welcome. I'll keep updating in hopes of helping someone else who goes through this...

Don't mind songgsan. It is a, well, I have no clue really what it is. Sometimes, computer users are created and they submit comments based on the original post or some random post. They get banned pretty quickly but are a PITA. Carry on.

So you've changed out all of your front hardware in terms of brakes, and you've replaced your master cylinder 3 times, as well as replacing your ABS pump. Hmm, and brakes are failing in the front. You have tried every bleeding method possible, and they still get soft. This may sound funny, but I didn't hear that you changed your brake fluid. You might have water in your brake fluid system. I know you might not have air, but let me know if you have fresh brake fluid.

If it isn't, I would:
1)Bleed one of the brakes until the system is empty.
2)Pull out that bleeder valve and inspect for contaminants.
3)Refill the brake fluid reservoir to the max line.
4)Bleed air out of brakes.

Check for leaks. I know you said you don't have any, but inspect up in crevices and such. If nothing, then it could be your master cylinder again. If there is a leak, then that would explain where your getting air/contaminants into the system.

 

[mliebal]

I know you have said you replaced the mc multiple times, but how much did you bench bleed those m/c's? I know on my 97 4runner, I did not get the m/c bled enough on the bench and it would never bleed the air out installed. I had to take out and bench bleed again in order to get brake pedal. Feels very solid now.
Just my experience. Goot luck!!