Hi all -

So I did the Tundra brake update last year - and ever since, I get an intermittent issue where for a single press of the brake, the pedal has to travel further before I feel pressure. Usually after this single press, the brake pedal behaves normally.

Brake fluid levels are fine, the car brakes fine and strongly. Most threads I see are about a consistent issue, but this is really intermittent. I might only feel it once in five drives.

What should I start troubleshooting?

I can attest for the consistent issues since doing the TBU a couple years ago. It's become habit for me to double pump the brakes at times to build up the pressure.

I also have no leaks, and a full reservoir.

Mike

That's odd, I've never experience that with the TBU, my brakes are always firm. I suggest bleeding the lines with the engine on and running since that's the only way to have the pump running and actively pushing the air out of the system (unless you have some fancy pressure system hooked up). I'm guessing and it's just a guess, you have an air pocket that is moving around, possibly might even be in the master cylinder.

Try to bleed the ABS system. You need Techstream to do it, but it will help little. The double pump is an issue, the soft first half of the pedal, is something I've tried to figure out on every Toyota truck I've owned.

You either have air somewhere in the system, or fluid is slipping by the master cylinder piston. Theres tons of information on ih8mud with the 100 series LC and this exact issue. Check that out. Lots of people end up rebuilding the MC.

Toyota vehicles and especially the trucks have handed my ass to me when dealing with the brake hydraulic system. There have been so many times that a Camry or a Taco comes in with excessive pedal travel or barely working brakes and having it be, in the end a master cylinder. I have replaced brake lines then couldn't get a pedal, replaced more parts, made sure the rear shoes were adjusted tight, drove it around and did ABS stops, pressure bled and finally replaced the master cylinder. I have also seen them intermittently act up like you described. If there are no leaks, the system is bled, the calipers are good, the rear brakes adjusted and the ABS light is off there's a good chance it's the master cylinder.

Fair enough. The truck is 20 years old and it’s been a champion. Recommendations for manufacturer for replacement? Can they be rebuilt?

You can rebuild a master really easy if you know how...cost is minimal and all you need is a small hone stone for a drill...YouTube is a great video source.

Sent from my SM-G955U using Tapatalk