Occasional hard breaking stiff pedal (3 Viewers)

[1lukeduke]

Good evening everyone. I have searched this with no avail. I have 60 series front disc brakes and disc conversion rear on my FJ40. I just did a 700 mile trip, some dirt some street. While driving occasionally, my brake pedal would become hard to push and I would have about 50% of my breaking ability. It would happen about 10% of the time. The majority would be on the off-road portion, but sometimes just on the street. Both my reservoirs are full and it appears that my vacuum line is fine.Wondering if anyone has an idea what would cause that. Thanks ahead of time for all your help.

Lucas

 

[fireflyr]

I had a problem with my proportioning valve on my dual disc conversion. Under sudden or panic braking the pedal would be rock hard, offering little braking. I ended up removing the valve from the rear brake circuit and the brakes work perfectly. Maybe yours is adjusted incorrectly. Back it off a turn or two and test the brakes.

 

[trainbufftony]

Booster check valve?