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Discussion Starter #1
IF I have a slight leak in the booster could I hear it? When? With my foot on the brakes or off? What would be some other symptoms? Is there a test procedure?

IF my front rotors were turned just a tad under "minimum spec" would the calipers adjust, or would I see reduced braking power?

Same question as above but for the rear drums. Rotors and drums are original and I was trying to keep them. We're only talking about 1 or 2/1000s.

Trying to ID braking problem. Rebuilt MC, new pads, new shoes, bled correctly but don't have quite the braking power I would have expected. If I try I can lock up the brakes and skid. With foot on the brake at a stop sign I hear a "hiss" —more so when the pedal is going down than when it is a the bottom, but it's still there.

Thanks.
 

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Do you know your engine's baseline vacuum? Check it again. Less vacuum now might point to a vacuum leak thereby causing the hiss. Of course if you can hear it from in the car I'll bet you'll find it real fast from under the hood.
 

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A couple of Thousands on the drum dia or rotor thickness shouldn't be an issue for you on your stated problem. I'm not sure where I'd draw the line on my own car but for safety items like brakes I'm not stuck in the 60's or on the original parts. I feel the engineers know better than I when they set the limits and they understand why.

Pedal height where it should be? pedal holds firm and doesn't pump up or fade down when held lightly (like at stop light)? If adjustment is correct I think it's probably a hydraulic issue.

Jeff
 

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As suggested, check pedal free play. if not enough, atmospheric valve will be open and a sight hiss may be heard.
Apply the brakes fully, and a hiss will be heard as atmospheric valve opens and allows diaphram to be pulled in by engine vacuum.

Calipers are self-adjusting and caliper should be at a perpendicular angle for a parallel pad contact.

Rear shoes have mininmal contact area due to the new overbore of the drum.
Shoes are designed for the OE diameter to match a new drum diameter.
Bore out the drum and diameter changes - think of a 3 inch diameter lid onto a 4 inch diameter bowl. Small contact between the shoe and drum.

A lost art - find an older shop and have them 'arc-turned' the shoes to the new diameter of the drum.
Take both the drum and its shoes and match the shoes to their drum.
Assemble brakes, pull parking brake to center shoes, release brake, tighten adjuster until wheel does not turn, then back up 5 notches. Then adjust parking brake for 6-8 notches at its foot pedal.
 

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Discussion Starter #8
Thank you everyone. All good things I'll check. I am unfamiliar with the term "atmospheric valve." What and where is that? Unfortunately the weather is going to get a little ugly here for a while, (7º here tonight) so it may take some time to get back to you. Appreciate all the ideas.
 
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