Hey all, I must be missing something simple, but can't seem to track down the root cause of the problem... '75 FJ40 with disk brakes -I think the first month of production. Original booster looks like it was for the drum brakes (the short one). New brake master cylinder, new lines, calipers (switched to disks in the rear), and fittings. I tried to bleed the brake system and ran into a strange issue. The rear brakes were not getting any fluid. I thought it may be the proportioning valve, nope. I eventually remove the fitting to the master cylinder (I already removed the check valve). No fluid transfer from the resevior to the outlet! I could see the piston articulating inside, but no fluid. The front brakes blead fine. I understand that my last course of action will be to remove the master cylinder and take it apart unless someone has any ideas. The cause must be trivial, brakes are not complicated and I have done them many times before. The differences that could possibly be part of the problem are: 1) I bought the master cylinder for my '79, but used it on this one. I wouldn't think this would be a problem since the fronts blead fine. It is an OEM MS, not an aftermarket product. 2) The original booster is not the tandem type that was used for front disk brakes - the big tandem one like on my '79. I suspect that my vehicle was one of the first that they switched to disk brakes on and didn't think the booster needed an upgrade till later. I don't really think that the booster would have anything to do with the problem though. Can I buy a clue? :dunno: I don't mind feeling stupid if it gets me a solution to the problem.