Master cylinder Replacement

[johnrem46]

Just redid front and rear calibers on my 77. Now the Master Cylinder is leaking.It seems to be leaking where it bolts to the power booster. I read a few other Threads it seems the boosters usually do not go bad? Do I need to replace the booster? What master cylinder do I need 1in or 1 1/8in bore? How do you bench bled the Master Cylinder?

 

[duke94]

Power Brakes use 1 1/8, manual uses 1". Sounds like the M/C is leaking at the rear seal. You need to replace or rebuild it BEFORE it destroys the booster. The photo below shows how to bench bleed.



Install a couple of tubes from the outlet ports to the reservoir. Fill the reservoir with clean brake fluid. Using a screw driver, slowly push the piston inwards until it stops. Release and repeat until air no longer comes out of the tubes.

 

[JohnZ]

Power Brakes use 1 1/2, manual uses 1".

Nope. Power brake master cylinders are 1-1/8".

If you don't have extra line and fittings lying around, the "Help" section at the auto parts store will have a bench-bleeding "kit" for about five bucks with an assortment of plastic fittings, two hoses, and a hose retainer.

 

[duke94]

Nope. Power brake master cylinders are 1-1/8".


I knew that, where the heck did I get a 1 1/2" from:confused