Sinking brake pedal (1 Viewer)

[Rob81]

I have a 1989 hj60 LandCruiser. I have recently replaced all the brakes with brand new components (all 4 corners). I have also put in a new 80 series booster and new master cylinder. Since doing everything I haven’t been able to get my pedal right again.
when the car isn’t running I have a good solid pedal (not sinking). Once the car is started I still have brakes but the pedal will slowly sink to the floor. I am using a good quality DOT3 fluid and have bled at least 3 litres through the system in different ways.
still has the same sinking pedal once started.
Any information or help would be appreciated.
Cheers

 

[g-man]

Any of these from the FSM...

 

[Rob81]

Any of these from the FSM...

View attachment 2733525

Everything on the whole brake system is brand new. I’ve bled it and have no air.
Tomorrow I’ll re check the booster pin and the rear drums are adjusted correctly.
I know it’s not much. Just something I’ve over looked but don’t know what.
Thank you for the check list. Much appreciated

 

[g-man]

when checking the booster, push on the pedal 3 or 4 times w/out the motor on and feel for things tightening up. then do the same with the motor running and if there is a leak in the booster the pedal will continue to drop.

 

[Godwin]

New master cylinder could be bad with fluid leaking around the seals. If you hit the brakes hard do you have an solid pedal? If you apply brakes gradually does the pedal sink? I've only dealt with bad MCs twice but in both instances these were the symptoms exhibited.

 

[Freewheel]

yep, sometimes master cylinders are bad out of the box. Especially if not made by toyota... but also possible for OEM ones to be faulty