Master brake cylinder - Impala Tech
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post #1 of 7 (permalink) Old 01-27-2015, 06:03 PM Thread Starter
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Master brake cylinder

Hi everyone. Need your opinion or fact, based on the following. I replaced my single reservoir master cylinder on my '62 Impala, with a dual reservoir master cylinder. This car is equipped with a power booster and has drum brakes all around. The ports on the mc accommodate a 3/16" line in the front and a 1/4" line in the rear. I ran a single 3/16" line from the rear brakes to the front reservoir on the mc. I used the rear 1/4" reservoir to feed the front brakes. I've been told that you should use the front reservoir for the front brakes and the rear reservoir for the rear brakes. If true, then I have it backyards. Both reservoirs appear to be the same size containing the same amount of fluid. I'm wondering what the difference is and if it does matter which reservoir feeds which line. I certainly want it correct and functioning properly. I will change it if it matters, but would like to hear from others first. Thank you, Carmine.
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post #2 of 7 (permalink) Old 01-27-2015, 06:28 PM
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Rear reservoir is for front brakes.

Your dual master is for a drum/drum car, correct?

Two doors, four doors, wagons, and ragtops.
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post #3 of 7 (permalink) Old 01-27-2015, 06:49 PM Thread Starter
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Yes, that is correct. The mc is for drum/drum and is new. Its for a '67 Impala. I just finished reading/researching some old threads here re. my issue, and as you mentioned, the rear reservoir is for the front brakes. I think I finally did something right. Thank you jos, Carmine.
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post #4 of 7 (permalink) Old 01-27-2015, 08:55 PM
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Good call, the 67 dual res is the go-to for single pot conversions.

Two doors, four doors, wagons, and ragtops.
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post #5 of 7 (permalink) Old 01-28-2015, 10:02 AM
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I just received my '67 dual reservoir the other day to replace my single reservoir. I noticed the push rod hole in the dual reservoir MC is very deep instead of just a shallow radius. Can you tell me if you needed a longer push rod? I haven't taken the old MC off the car until I get the 2 gen Trans Am out of the garage and make room for the Impala.

Thanks.
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post #6 of 7 (permalink) Old 01-28-2015, 01:34 PM Thread Starter
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Quote:
Originally Posted by wannaSS View Post
I just received my '67 dual reservoir the other day to replace my single reservoir. I noticed the push rod hole in the dual reservoir MC is very deep instead of just a shallow radius. Can you tell me if you needed a longer push rod? I haven't taken the old MC off the car until I get the 2 gen Trans Am out of the garage and make room for the Impala.

Thanks.
No, I didn't need a longer push rod. But here is what happened. I bought a dual reservoir mc from a vendor who said it was a bolt on with nothing else needed. After it arrived and before bench bleeding it, I tried it on for fit. No good. I looked at the push rod hole in the plunger which was very shallow. I looked at my old single reservoir one, and the hole was deep. Obviously, not the same. Did some research and it was suggested that a '67 Impala 1" dual reservoir for drum brakes would work. Found a Bendix brand one at Rock Auto and ordered it. When it arrived, the plunger had the deeper hole and I measured it against the old one; same identical depth. Bench bled it and then struggled to get the brakes bled. Just a whole lot of air in the system. I think I'm finally done with it. Also have to mention and I'm not sure it matters, but I have factory power brakes which the booster has its own rod. Best wishes with yours, Carmine.
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post #7 of 7 (permalink) Old 01-29-2015, 10:41 AM
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Thanks for the response Carmine. The dual MC I bought has a deep hole for the push rod so from what you have said it is probably correct.

So many people struggle with brake bleeding. The absolute best way is to bench bleed the MC in the horizontal position on a bench, then use a pressure bleeder attached to the MC or a vacuum bleeder attached to the bleeder valve at the wheel. Tap the caliper or wheel cylinder to dislodge air bubbles as you bleed. Some will say start with the wheel farthest from the MC and work backwards but I have seen GM service manuals describe that sequence in both nearest or farthest to start.
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