Solved - Brake Pedal clunk/bump/sound

[JerEazy]

So I’ve been chasing down these weak brakes for a while. Better now after bypassing ABS and it’s 3rd 2 man bleed. But still feels like a lot of travel before engagement and underpowered. I keep an extra following distance because I am positive an emergency stop wouldn’t happen.

I was doing the brake booster test where you pump the brakes up and then start the car and see if the pedal goes down. When pumping up this “clunk” or “skip” happens about halfway through travel before hitting the bottom. When starting the pedal drops to the floor as I guess it should. But this “bump” in the pump has me wondering if something else is wrong. There are no leaks - did a lot of checking on that front. Any thoughts?

I took a video of it - but not sure how to upload here. But here is YouTube Link

 

[robnicko]

i looked at your video, id be checking the linkages & bushes under the dash where the pedal pivots as well as the clearance between the pushrod of the booster to master cylinder clearance.
But hearing the sound to me indicates a worn bushing on the pedal pivot somewhere

 

[JerEazy]

i looked at your video, id be checking the linkages & bushes under the dash where the pedal pivots as well as the clearance between the pushrod of the booster to master cylinder clearance.
But hearing the sound to me indicates a worn bushing on the pedal pivot somewhere

Not sure how to check the clearance you mention - it’s not a bushing by feel but I’ll get under there and check.

I would think that after a few pumps eventually the pedal gets so hard that pumping isn’t an option anymore. That never happens here.

 

[robnicko]

this,

 

[JerEazy]

this,

I see what you’re saying - maybe the pushrod is too recessed and the sound is perhaps when it contacts the piston in the master

 

[jonheld]

I see what you’re saying - maybe the pushrod is too recessed and the sound is perhaps when it contacts the piston in the master

All of the information and specifications are in the Toyota factory service manual (FSM) which is a free download from the resources section.

 

[JerEazy]

All of the information and specifications are in the Toyota factory service manual (FSM) which is a free download from the resources section.

I’ve got a hard copy at home as well. So I’ve got a project for the weekend.

 

[JerEazy]

I am so effing happy you guys recommended to check this.

The arm of the brake booster was all the way in. And the contact point of the master cylinder is recessed in a good inch - maybe 1.5. So the first half of pedal travel was nothing. That clunk I was hearing was when the piston actually got far enough to apply pressure. Adjusted it out and holy crap what a difference. Almost makes me want to reinstall the ABS!!!

If you haven’t checked your clearance - do it just for good measure.

Thanks again