nm9stheham
Well-Known Member
Here is what might have happened. The original drum brakes take very little fluid to move the wheel cylinders. The new calipers take a LOT to move the pistons into place initially to close the original gap between pads and rotor. It may be that you bled the new fronts with the pistons in the calipers all the way recessed, and that is fine as long as a bleeder is open. But when you closed off all the bleeders and started applying the front brakes, the pistons move out of the bores to take up the slack, and it sucked all the fluid down out of the reservoir.
This is the problem with the 67 drum/drum MC: the MC reservoirs just don't have to capacity to put all the fluid required into the calipers piston bore as the pads get into place and then wear. You just had it happen right off the bat, instead of after some pad wear. Guys who use the old drum/drum MC's have to keep adding brake fluid as the pads wear (and then suck most of it back out as they push the caliper pistons back in to replace pads to keep it from running all over the place and ruining the paint) . The 73-76 MC has a rear reservoir with 2 or 3 times the fluid capacity versus the MC that you have to address this issue.
Re-bleed the fronts, and then keep adding fluid and them pump 2-3 times with the bleeders closed and then recheck the fluid level, to see if eventually you get hard pedal and front brakes. If so, then this was the problem.
This is the problem with the 67 drum/drum MC: the MC reservoirs just don't have to capacity to put all the fluid required into the calipers piston bore as the pads get into place and then wear. You just had it happen right off the bat, instead of after some pad wear. Guys who use the old drum/drum MC's have to keep adding brake fluid as the pads wear (and then suck most of it back out as they push the caliper pistons back in to replace pads to keep it from running all over the place and ruining the paint) . The 73-76 MC has a rear reservoir with 2 or 3 times the fluid capacity versus the MC that you have to address this issue.
Re-bleed the fronts, and then keep adding fluid and them pump 2-3 times with the bleeders closed and then recheck the fluid level, to see if eventually you get hard pedal and front brakes. If so, then this was the problem.
