Subaru Master Cylinder Upgrade........ - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 03-15-2007, 05:36 AM Thread Starter
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Subaru Master Cylinder Upgrade........

Just a couple of items that need clarification before I get into the nitty gritty…

*This upgrade is not my brainchild. This is Yankee Tim & Yankee Bob’s baby. They “discovered” it and made it work so the credit that is due is theirs. I am merely the beneficiary of their research, testing, and generosity. I’m only documenting what I did for others to see. That said, thank you to Yankee Tim & Yankee Bob……

*The specific year/model Subaru isn’t cast in stone as of yet. From what I’ve found so far on Napa’s site is that a 1998 Legacy with ABS appears to be an exact match to the one I’m using. I’m sure there are other models/years that will work as long as it has a 1 1/16” bore.

*If you have the original brake proportioning valve, you might want to consider replacing it. I've had used a few "good" used ones, but they eventualy leaked. After all, they are nearly 20 or more years old. I once did a "autopsy" on one and discovered that they can leak internally for quite some time with no external sign of the leak. I replaced mine with a new one just to be safe.

A couple of items you’ll need:

Subaru master cylinder (1 1/16” bore for ABS) as compared to Suzuki's 7/8" bore

Subaru master cylinder wire connector Master cylinder to booster gasket (or RTV silicone)

Small tube bender

6mm x 1.0 bolt, app. 50mm long (grade 8.8 or better)

The swap:

Remove original master cylinder. Save gasket if possible (use old gasket as a template for a new one).
Reach into booster and remove the booster push rod.
Remove the “tip” of the pushrod.
Cut the head off the new 6mm bolt.  Clean up threads by “chasing” with a die.
Round off one end with a grinder to make the new booster push rod tip. As an option, you can use a 6mm acorn nut, grind off the corners of the hex, then loctite it on.
The original push rod length was too short, so the new push rod will have to adjusted to the proper length. There needs to be zero tolerance between the tip and it’s mating surface inside the master cylinder. This will take a couple of minutes to adjust properly.
If the Subaru master cylinder doesn’t have an “O” ring on it, swap the Suzuki one onto it.
Once the pushrod is adjusted properly, Bolt up the master cylinder after you’ve bench bled it. Use the gasket you cut or RTV.
Using a tube bender, bend the brake lines to mate to the new master cylinder.
Splice in a connector (Subaru) to the Suzuki wires.
Bleed the brake system.
Enjoy the improvement in braking.

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Attached Images
File Type: jpg Zook-Master-Cylinder.jpg (120.0 KB, 6 views)
File Type: jpg Subaru-Master-Cylinder.jpg (93.4 KB, 2 views)
File Type: jpg Bore-Diameter-Comparison.jpg (57.3 KB, 2 views)
File Type: jpg Length-Comparison.jpg (80.6 KB, 2 views)
File Type: jpg Rear-View-Comparison.jpg (96.2 KB, 2 views)

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Crow

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post #2 of (permalink) Old 03-15-2007, 05:41 AM Thread Starter
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More pics........
Attached Images
File Type: jpg Subaru-Bottom-View.jpg (51.3 KB, 3 views)
File Type: jpg Subaru-Side-View-A.jpg (72.6 KB, 1 views)
File Type: jpg Subaru-Side-View-B.jpg (64.2 KB, 1 views)
File Type: jpg Suzuki-Booster-Pushrod.jpg (118.1 KB, 1 views)
File Type: jpg Modified-Booster-Pushrod.jpg (103.7 KB, 2 views)

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Crow

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post #3 of (permalink) Old 03-15-2007, 05:47 AM Thread Starter
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The last pic is from a 2005 Impreza. It appears that this is what I'm using, but can't verify this as of yet........
Attached Images
File Type: jpg Optional-Tip-Mod.jpg (126.3 KB, 1 views)
File Type: jpg Passenger-Side-View.jpg (94.3 KB, 1 views)
File Type: jpg Front-Side-View.jpg (84.3 KB, 1 views)
File Type: jpg Front-View.jpg (81.5 KB, 1 views)
File Type: jpg 2005-Impreza-Master-Cylinde.jpg (77.1 KB, 1 views)

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post #4 of (permalink) Old 03-16-2007, 10:23 PM
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Nice writeup, Crow.
I'm opting for the Firebird unit unless I can actually find a Suby around here.
Sarge

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post #5 of (permalink) Old 03-18-2007, 07:12 AM Thread Starter
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Thanks Sarge! But I did the easy part. Tim & Bob did the hard stuff.......

All Good Medicine,
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