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Old 04-02-2015, 06:09 PM
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Drum brake rebuild issues

I rebuilt the brakes on a '65 Galaxie. The car has drums all around. It was originally a single resevoir. I converted to dual by going from the MC straight to the rear with one port. The other line goes to the factor splitter.

I replaced the MC, hard and soft lines, wheel cylinders, shoes, hardware, cables and hardware. I only kept the booster and the drums that were turned.

I took it out of the garage yesterday and the pedal was low and hard. It took effort to stop from idle.

I bled the brakes and adjusted the drums. I can only spin the wheels about a 1/4 turn.

Would they need to be adjusted further? Is it possible it is due to the MC bore?
I bought the MC for a 67 with drum/drum. However it does look like a disk/drum MC.

I was told the booster was replaced about 5-10 years ago.

Any ideas?

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Old 04-02-2015, 06:31 PM
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If the pedal was low and hard then your booster is shot or you don't have enough vacuum to work it.
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Old 04-02-2015, 07:18 PM
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I would want to know for sure what the master cylinder bore size is.
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Old 04-03-2015, 05:26 AM
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. Put your foot on the brake and start the engine... the pedal should lower a bit as the booster receives vacuum from the engine...

. If the master cylinder was bad and leaked brake fluid back into the booster, it may have damaged the diaphragm in the booster...


. The vacuum line from the carb. to the booster should have a one-way step valve in it somewhere's to hold vacuum in the booster...


. Does your engine have a big performance cam in it that reduces vacuum?


. Do you have access to a vacuum gauge to test the amount of engine vacuum? Need about 12" of mercury or more of vacuum...


. Was the front line going to just a simple little 3-way splitter and not a larger proportioning valve?

. Measure bore of old and new M.C.'s... prolly don't have to remove lines, just unbolt and pull forward enough to measure...


. When couldn't turn wheels a full revolution, just means you adjusted the shoes a smidge tight, but since can move them at all, prolly OK... they will quickly make some clearance and seat in when used a couple times...
.
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Old 04-03-2015, 07:34 AM
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Sounds like the shoes are way too tight if you can only get 1/4 turn when spinning them. Also sounds like you may have a booster or vacuum issue. If you already had the booster with the old master, and nothing changed there, then I'd be checking the operating rod and new master, to ensure they were made to go together. You may have the wrong clearances between the booster and new master, if the rod is depressed when it was assembled.
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Old 04-03-2015, 10:45 AM
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I checked with Cardone. The MC has. 15/16ths bore. I am going to separate the vacuum lines and try again.

I bought the car on 1/1. I have only driven it on and off the trailer.

I wanted to go through the brakes before driving it. All the lines were really rusted.
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Old 04-03-2015, 02:13 PM
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I can't remember if there were dual MC before disk/drum combos but a disk/ drum MC on an all drum system probably has residual valve issues. Personally I would have stuck with the stock reliable fruit jar MC until I converted to disk/drum rather than some jury rigged system.
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Old 04-03-2015, 09:26 PM
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Quote:
Originally Posted by RODSRUS View Post
I can't remember if there were dual MC before disk/drum combos but a disk/ drum MC on an all drum system probably has residual valve issues. Personally I would have stuck with the stock reliable fruit jar MC until I converted to disk/drum rather than some jury rigged system.
No, dual reservoir conversions are done all the time, and no residual valves are needed. The brakes don't know if they're getting hydraulic fluid/pressure from a single reservoir, or a dual. I've done a number of them, and as long as the master is higher than the wheel cylinders, there's no need for a residual valve in a drum/drum setup. My '63 Falcon gasser is 4 wheel drums, with a later Mustang dual reservoir, and works just great.
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Old 04-04-2015, 06:16 PM
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My concern was that drum single MC have a built in residual valve which must be removed in a disk/drum system and a residual valve added to the rear drum brakes if the MC is mounted low. You are right for high mounted MC (which is true for the '65 Ford) no built in residual valve for dual MC. Just be careful for under the floor MC (mostly pre 50's).
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