Brake pedal goes to the floor

[roversii]

I finally got my '60 Series II 88 running only to find the brake pedal goes straight to the floor. Brake fluid level is fine. New master cylinder 2 years ago. Any suggestions on how to troubleshoot? For what it's worth, the clutch works fine.

Many thanks!
David

[jp-]

If the fluid level is not going down, most likely the MC has blown an internal seal, and will need to be replaced. However, look up under the pedal (from the floorboard) to make sure that the linkage is actually moving the rod in and out of the MC.

[cedryck]

check mechanical linkage first, is pedal moving plunger at MC? if so sounds like JP might have the next step, best of luck,

[erik88lr]

If the fluid level is not going down, most likely the MC has blown an internal seal, and will need to be replaced. However, look up under the pedal (from the floorboard) to make sure that the linkage is actually moving the rod in and out of the MC.

The pedal linkage may be moving the rod in and out of the MC, but if the MC innards are jammed forward for some reason it'll just flop that rod back and forth without moving any fluid. See https://www.roversnorth.com/parts/plc752_master_cylinder_early_cv for picture of an MC with a rod that's not directly connected to the MC piston's plunger, only pushes on it. Suspect you'll have to take the MC off and apart to get things moving again, put in new seals and flush the system to get pressure back.