Proper 1965 Power Booster pushrod adjustment from Ford Service manual - Vintage Mustang Forums
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Old 11-02-2004, 06:28 PM   #1 (permalink)
HoosierBuddy's Avatar
Join Date: Aug 2002
Location: Probably in the garage
Posts: 6,364

mmancuso13 posted yesterday that his power brakes were locking up and the pedal was staying stuck to the floor. I had the same issue many years ago on my '65. I dug the following information out for mmancuso13 from the 1965 Ford shop manual. Hopefully it will cure his brakes. I know it fixed mine.

I just wanted to make a post to the forum so it will be available on search from now on.

From 1965 Comet, Falcon, Fairlane, and Mustang Shop Manual

Part 2-1 General Brake Service

Power Brake Master Cylinder Push Rod Adjustment - Comet and Mustang

"The push rod is provided with an adjustment screw to maintain the correct relationship between the booster control valve plunger and the master cylinder piston. Failure to maintain this relationship will prevent the master cylinder piston from completely releasing hydraulic pressure and can cause the brakes to drag , or cause excessive brake pedal travel."

The shop manual then goes on to describe a guage that can be fabricated to check this dimension. The gauge is to be made of 16 gauge sheetmetal. It is rectangular in shape with dimensions of 2 7/8" by 1 3/4". A 3/4" wide notch is centered on one of the long sides. The notch is to be 0.970" deep minimum to 0.985 inches deep maximum.

<----------------1 3/4"-----------------> By 2 7/8" tall

|xxxxxxxx| .970" - .985" by 3/4"

"To check the adjustment of the screw, fabricate a gauge of the dimension shown in Fig. 2. Then place the gauge against the master cylinder mounting surface of the booster body as shown in Fig. 3. The push rod screw should be adjusted so that the end of the screw just touches the inner edge of the slot in the gauge. Do not set up side forces on the push rod. Side forces may break the valve plunger.

This is an approximate adjustment only. The master cylinder piston should not move more than 0.015 inch as it contacts the push rod. No movement (exact contact) is ideal."

Figure 3 shows the gauge sitting against the booster with the master cylinder removed. The gauge sits flush on the housing at its highest points which are near the mounting studs for the master cylinder. The push rod fits into the 3/4" slot and the screw is adjusted out to just touch the gauge.

You could approximate this measurement by placing a straight edge across the booster face and then using depth gauge to measure out to the tip of the adjustment screw. Add the thickness of your straight edge to the measurement of the depth guage and compare that to 0.970" to 0.985"


"Two barks means faster!" Enzo
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