Thread: Brake problems

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Yeah Mike and then there's that problem that I have with the car

This has been an interesting thread, and it's full of wild guesses and faulty information!
1. Your m/c is a "Corvette" style, and is plumbed correctly. If you remove the cover, you'll be able to see that the rear reservoir will hold more fluid than the front reservoir. Notice the bulge in the side of the casting. The large (rear) reservoir goes to the front brakes. You can't tell by looking at the cap, as the cap is symmetrical. It DOES make a difference how it's plumbed!
2. The adjustment of the push rod between the booster and the m/c is VERY critical. There is a small fluid port in the bottom of the reservoir that MUST be uncovered by the pistons when the brake pedal is released. This can be checked by watching for a little spirt of fluid when the pedal just starts to move. If you don't get a spirt, remove the m/c from the booster and shorten the push rod in the booster until you get the spirt. If you get a spirt only after moving the pedal 1/4 inch or more, lengthen the push rod. Having too much movement before the spirt will cause the brake pedal to travel too far before the brakes work (maybe to the floor). You don't need to have vacuum on the booster for this test.
3. You can't plug one brake line, and then try to test the other line. The pressure will immediately build up in the blocked section of the m/c, and will not allow the other section to push any fluid.
4. Call SAC Hot Rod (714-997-3433). They have built lots of cars with this type of brake system.

Hot Rod Roy,


For one , this is not a vette style master. I did however find out that the pic of the master cylinder that you saw is from a GM all drum brake setup (far as we can figure) so there's part of the problem.
As for the problem at hand , as I said the end on the booster rod does not have enough threads on it and I can't adjust it out to where it pushes the rod
and piston far enough to create any pressure .
Denny had it right on the 4th post I should have checked it a 2 nd time.
But one thing I can say is I'm glad that these guys at least offered the help weather it be right or wrong.

Rocky, if your master is from a four wheel drum brake car, there might be internal residual check valves in it. This would cause your disc brakes to drag all the time, since these residual check valves would hold about 10 psi on the calipers. You can check for these valves by carefull inserting a straightened paper clip into each outlet port. If the paper clip only goes in about 1/4 inch, you've got internal check valves. If the paper clip goes in to the centerline of the master cylinder, there are no valves.

True, this master is used on several GM vehicles, including vans. Take a look at an '82 or earlier (back to '68) Corvette . . . same m/c (but no internal residual check valves).

Have you checked the diameter of the bore in your m/c?