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Old 04-14-2011, 01:27 PM
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Troubleshooting 8" Dual Diaphragm Booster

Now bear with me... but this is installed on a Jeep.

It's one of those popular generic eBay units, like shown here:

Now I know this is a hotrodders page, and not a Jeeps page... but it seems like these units are more typically used in rods, so I thought I would pick your brains (if you don't mind). The vendor I purchased it from on eBay, while initially helpful, didn't seem to interested in really helping me out.

The story:
Purchased one of these units for my 1983 Jeep CJ-8 Scrambler.
The problem I keep having is that the "plunger" (What I call the rod that extends from the booster into the master) stays extended. Now I know what you're thinking: "Your pushrod connected to your brake pedal is too long!" It's not. It freely flops on and off of the brake pedal.

After driving for a few minutes I can feel the brakes being applied. When I stop and remove the master cylinder from the booster I can see the plunger extended a good .5" further than it should be. At this point I can either A) pump the brakes until it returns to the correct position, or B) press it back in with force. While the plunger is in this extended position I can freely remove the pushrod form the brake pedal, and jiggle the linkage around. I can even remove the entire booster and with no force whatsoever on it from the back the plunger stays extended.

When I told the vendor this they promptly sent me another (albeit used-looking) booster. The problem is still there.

Thoughts? I'm about one day from hosting a Jeep-be-que.

Thank you rod-dudes!

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