Brake pedal suddenly went to the floorboard

SG1952

MEMBER
1987 MAZDA TRUCK
4 CYL
2WD
MANUAL
70,000 MILES

My son was driving my B2000 truck yesterday, when he said the brake pedal suddenly went to the floorboard and the brakes would not work. He pumped the pedal a number of times and they finally engaged. I first thought we had blown a wheel cylinder, but when I checked today, there did not appear to be any leaks and the master cylinder was full. I test drove the vehicle and the brakes seemed to work fine. However, I can't trust it right now. Could it be the power assist mechanism? Thanks.

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

This could be due to a malfunctioning master cylinder.
Bad seals inside the master cylinder will not allow the brake system to build pressure when it gets applied.
Which will cause the pedal to go to the floor and it will have little to no pressure.
That will lead to very weak braking performance.

Take a look at this helpful guide:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Please let me know if you have any questions.
Thank you.