Help with brakes

Hi
I’ve been a mechanic for over 30 years, but with this one, I am stumped.
My 2006 Toyota Tacoma 4.0 L 4 x 4 with 115,000 miles had a spongy pedal.

The master cylinder and rear wheel cylinders were original equipment. I had changed the front brake calipers before but was over 10 years ago.

Decided to replace everything, calipers, brake pads, brake lines, brake shoes, drums, rotors, wheel cylinders.
I suction bled the brake system, but it was still spongy so I did a gravity bleed. Still spongy. I brought it to a friend of mine that has his own shop and he tried to bleed it, but said the master cylinder is bad or the ABS unit. There are no codes for the ABS unit, so I replaced the master cylinder with a higher quality aftermarket unit. I thoroughly bench bled and capped the ends to confirm pressure. Still has a spongy pedal.

I took it to the Toyota dealership for diagnostic. they did a gravity bleed and tried to figure out what was wrong, but only came to the conclusion that the master cylinder should be replaced because it’s aftermarket unit.

they confirmed all air has been removed from the system and that the ABS is functioning fine.

Any ideas would be greatly appreciated. I had an old FJ 40 that had brake issues similar with a spongy pedal and I had to do a reverse bleed starting with the tire closest to the master cylinder get to get it to work.

thanks
Mike

 

I dont know if this will help you out or not but I noticed a huge improvement in brake pedal firmness when I replaced front and rear brake lines with stainless braided lines.

 

I have seen ABS units do this multiple times although not very often on Toyota.

If you have a bi-directional scan tool you can command the valves in the ABS and see if any make a difference in the pedal.

 

I do have access to the scan tool and I saw that information on Mitchell one software, but when I took it to the dealership, they said you do not have to do that for my 2006 model.

they confirmed the ABS module is working fine and they had removed all air from the system

 

Are the rear brakes adjusted correctly? How's the parking brake? Does it set firmly?

 

Rear adjustment is where I was going....

 

1) no chance the front calipers are on upside down/wrong sides?
2) brake booster push rod length properly adjusted?

Those are the 2 most common issues I've seen with brake issues. If those are good and no air in system, everything should work.

 

Rear brakes are adjusted correctly, and the parking brake is firm.

front right & Left calipers are mounted correctly. Bleeder screw is at the top of the calipers

pushrod lengths adjusted correctly, using the special tool provided- at zero clearance

 

Hmmm and no vacuum issues with the booster and booster and master properly sized and lines hooked up correctly front and rear to the master? Any proportioning valve adjustment on there?

I know you can make the ABS modules activate to force bubbles out on a per wheel basis, but it's a fairly involved process. A shops pressure bleeder should accomplish that same function as well though. That's a somewhat common issue on my gen of Supra, but more often than not its one of the other ones I've mentioned. Brake issues are frustrating as hell man, good luck.

 

My money is on the ABS unit if the rear brakes are properly adjusted and there's no air in the system. I've seen quite a few Ford, GM, and a couple Toyota vehicles do that, sometimes you can go find some gravel and do a couple ABS stops and it will fix it if there's just some trash in one of the valves.

 

If your truck uses the standard vacuum booster, you do have to purge the ABS pump.
Unless you were super fast on the wheel cylinder change and know for SURE you got no air into the pump.

I wouldn't take the dealerships word, since they probably don't know what they are talking about.
There were some trucks that used the a different booster, but it was SUPER RARE on anything before 2009.

I'd want to know for sure that they, dealership or who ever, DID do the ABS bleed procedure.
Vacuum bleeding won't work......

When I did my rear axle seal, I got air in the ABS pump.
I had to go to a gravel parking lot and do the "slam on the brakes" bleed.

Thankfully, the rear bleeder is easy to get to.
And I had my brother to help.....(Hold the pedal down).


I now have a scan tool........

 

Thank you for everyones help

gonna recheck the rear brake adjustment after the shoes and drums break in a little bit more then try activating the ABS

 

Watching…

 

Can you pump up the pedal with the engine off and get a firm pedal?
I just went through this with mine. When I bought it the pedal had excessive travel and the e brake was low.
Replaced the worn out shoes and replace the drums/wheel cylinders with oem. Was much better but still didn't "feel" right .Didn't stop the way I thought it should. Bled the crap out of it. Pedal and e brake felt okay, but still didn't feel 100%.
Anyway, just kept driving it and gradually I think it took quite a while for the shoes to bed into the drums and eventually it felt pretty good. Have since replaced the original rotors(19 years old)and pads(with oem) and now it feels like it should.
*Retired auto tech with over thirty years of experience

 

I hated the brake pedal feel on my 2008 X-Runner since the day I drove it off the lot (in 2008). I even took it back to the dealership, and the technician said it's the way they normally feel. I've owned several different vehicles, from previous Toyotas, BMWs, Acuras, Porsche, Chevrolet, etc. and none had that "stepping on a mushroom" feel like my Tacoma.

I eventually got rid of it a few years ago when I installed a BBK and SS brake lines.

 

Sounds just like my 2019 Jeep Wrangler. Like previous replies, a few runs down a gravel road w/ several slams of the brake pedal were enough to get the air to purge from the ABS system. I would bet the farm that that's what's going on here.