GThe brake pedal on my 1996 2WD Mazda B3000 (auto trans) occasionally sticks down just enough to trigger the brake lights. It doesn't seem to be enough to engage any braking action.

I inspected the brake pedal itself and it's not "rocking" like some videos I've seen with the manual transmission vehicles - they even make a replacement bracket for those with a clutch.

Brake booster and master cylinder look pretty new - probably replaced by the guy whole sold me the truck.

I lubed the pivot shaft on the pedal, but it still sticks enough to trigger the brake light occasionally.

Any ideas? Thanks

 

Could be the installer of the new master/booster didn't adjust the nut on the booster shaft so it fits tight against the Masters piston

There is no "return spring" on brake pedal, the piston in master and the booster push the pedal back up

Loosen and remove the 2 nuts holding master to booster, pull master away from booster and you will see the acorn nut you can adjust out, it should press slightly against the masters piston when its put back into place, and push brake pedal up all the way

If its unclear, Google: adjusting power brake booster nut for new master

 

Thanks again, Ron. That's one suggestion I had not considered.

Right now, I'm thinking it just may be the plastic bushing, part 2A309 in the pic below. Haven't been able to pull things apart this weekend - raining and crappy all day today.



Maybe I've been lucky, as I've only had to replace one vacuum power booster in my life, and that was on a 1976 Chevy Chevette (new wife's POS car) right after getting married, so make that somewhere around 1985 or '86,.

Spent a little time googling how this stuff works, and really enjoyed this video:


Besides being very well done, the video is worth watching just to see when he uses a special tool called "snap ring pliers" right around the 2'30" mark. If that doesn't bring a smile to your face, nothing will!

Kind of weird that Ford didn't add a spring to pull back the brake lever like so many other cars. Will post back once I get a chance to pull that brake pedal assembly apart. Probably not 'til next weekend, Cheers!

 

You will know if the top pivot bushing is worn out, it will wobble

 

Finally took things apart and figured out the problem: the pivot the brake pedal rides on was too stiff for the brake switch sping to overcome the friction. I disconnected the brake lever from the push rod, sprayed oil on both ends of the pivot, and then worked the brake pedal back and forth from dash to floor about 100 times until the pivot loosened up. Reassembled everything and now you can feel the pedal jump back a bit when you release pressure.

It's kind of an odd design compared to non-Ford vehicles. Found this drawing on a Mustang forum showing how the brake switch works. Added note on the pivot that was sticking.