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Discussion Starter #1
2008 Tundra, 5.7, 4x4, 93k miles.
The truck has been in very good condition overall.
Owned it for 1 year. Brake function has been flawless. Brakes engaged with very little pedal travel, grabbed very predictably, and have been dead reliable. A very solid brake system overall compared to most other vehicles I've driven.

I use the truck for work, including often pulling a landscaping trailer. Not heavy weight, but usually ~3k lbs.
Towed a single axle trailer for a while, and recently got a double axle with electric brakes, but I do not have a brake controller yet, so all the braking has been done by the truck. I thought it was okay until I get the brake controller as I was pulling light loads, similar to what I pulled with my single axle w/o brakes.

Doing work. Brakes are perfect. Park. Come back 30 minutes later. Immediately, upon shifting into drive, the brake pedal goes almost to the floor. A very obvious change. I check brake fluid level, check under the truck for leaks while pumping pedal, nothing.
I drive the truck carefully, it has lost nearly 70% brake capacity.

I park it. Come back the next day, brakes are perfect again.
Drive it later that day, brakes start out perfect, then suddenly go mushy while driving. A few minutes later, perfect again.

My truck is black, and it has been quite hot here. My first thought was the ABS module is overheating, or a computer circuit board has gone faulty as I have seen in BMWs. With a BMW I owned, the ABS, brake, and traction lights came on. My Tundra has no lights on the dash. A scan with a semi-professional tool showed no codes, pending or current.

I bleed the brakes using a vacuum bleeder. The fronts were standard. My left rear bleeder screw was like 'loose' in the threads? I cracked it open, and my vacuum bleeder couldn't suck any fluid but it would dribble out via gravity, and the bleeder hissed. The bleeder screw was loose in the threads, very weird. The fluid was a bit dark.
The truck has not gone back to 'perfect mode' since, but the mushy mode has gotten slightly better. I tried to activate ABS multiple times to maybe purge the ABS pump.
I was pulling the trailer, and my front wheels locked up very easily. It was also wet out. After a while, I realized that my fronts were locking up far too easily and that my rears are not doing any work.
Autozone gave me the wrong bleeder screws for the rear, so I decided to use teflon tape to tighten up the threads just to be able to bleed the system.

Bled the rears again, the mushy pedal got slightly better but still quite dangerous in my opinion. I can feel a slight 'catch' about 1/3 down, then it travels further. Like when 1 caliper is good, but the 2nd is not so it requires more travel.

Is there something I'm missing here? I have bled many brake systems in my life, and tried to refine my procedure - pumping slowly, with lower amounts of vacuum to avoid creating micro-bubbles, always keeping the reservoir topped off, etc.
Do I have to purge the ABS pump somehow? Maybe via Techstream?

Thanks for the help.
 

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Start off by bleeding the rear proportioning valve, then do the rear wheel cylinders. I had the mushy pedal for a while after I did axle seals and just bled the wheel cylinders. Got back under the truck and bled the proportioning valve (it’s mechanically load sensing, mounted to the frame above the rear axle) and then bled the wheel cylinders and it was all perfect again. Whatever you do, get the right bleeders though. Even if that means going to a Toyota dealer and paying twice as much. It’s not worth the risk of using janky or incorrect bleeders.


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I’m sorry. What I said may not apply. I thought this was posted in the first gen section. That’s my fault


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