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Unread 09-04-2012, 04:20 PM   #1
toadman81
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1982 CJ7 
 
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power brakes, very hard to stop cj7

My 82 laredo came with power brakes. Since I've had it, the brakes have never been that good, but now it's to the point I don't want to drive it in fear of not being able to stop in time. They are mushy and you have to pump the brakes to stop. I bleed the brake lines recently and flushed out some nasty fluid, but she now has clear, fresh fluid. My guess is the master cylinder needs to be replaced or rebuilt. So here are my Jeep noob questions:

1) am I diagnosing this correctly?
2) what type of master cyldiner should I get?
3) Is it worth it to upgrade to a dual 8" diaphram kit like these?

http://www.ebay.com/itm/Jeep-CJ-1974...889124&vxp=mtr

or

http://www.jeep4x4center.com/power-b...-pbuj7486.html

Brakes = saftey, so I want premium and reliable parts to stop this beast. Thanks in advance folks!

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Unread 09-04-2012, 04:29 PM   #2
CJunk
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If you are not losing any fluid, it could be the rubber portion of the brake lines expanding. But, most likely it is the master cylinder. I bought the ebay kit. It is worth it, but I had to cut the pushrod and add new threads to it, because the brake pedal was too high. Other than that it was an easy install.
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Unread 09-04-2012, 04:39 PM   #3
Dadamsnv
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I'm guessing squishy brake lines or bad MC if you are sure there isn't any air in it. I swapped my manual brakes with a YJ power brake system. I had to lengthen the push rod and buy brake line adapters. Otherwise it bolted straight up and works fantastic! It actually brakes a little too hard if anything. My best mod for ~$100
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Unread 09-04-2012, 08:00 PM   #4
jeepdaddy2000
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Be sure all drum brakes are properly adjusted. If they are sloppy, it can take a pump or two to get the shoes against the drums.
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Unread 09-05-2012, 02:16 AM   #5
Mickey_Mouse
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Unread 09-05-2012, 04:35 AM   #6
Hawk4097
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I would just buy a new master cylinder. They are not that expensive. It just makes it easier.
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Unread 09-05-2012, 05:44 AM   #7
adman02
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I had a similar problem - power brakes on my 79 CJ7 and it had terrible braking (never quite sure I'd stop in time). I swapped in several different MCs and nothing helped. I did the YJ brake swap and about put myself through the windshield the first time I tested the brakes.

Thinking back, I suspect the power booster may have been bad. If changing the MC doesn't do the trick, you might change out the vacuum booster to see if that helps. Slightly easier to do than swapping in a YJ system.
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Unread 09-05-2012, 06:37 AM   #8
gazzo
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Takes almost forever to get all the teeny bubbles out of a new master cylinder. Makes a massive difference when you do

Here's something else. Pull on your e brake until it holds. Push down on your brake pedal and off again Let the e brake go only 1 tooth. Push down on the brakes again. If you have good "pedal" or "feel" then you need to adjust your back shoes.
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Unread 09-05-2012, 10:18 AM   #9
BlkCJ7Laredo
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Quote:
Originally Posted by Mickey_Mouse View Post
If you have a V8 and had the dual booster, you would have no problem. I bought a booster similar to that in pricing, it wouldnt fit on the brake pedal, the pushrod was different, and very little clearance between the booster and the carb, I had upgraded to a motorcraft 2100. I returned it for a OEM unit, power brakes and master cylinder.
I noticed the same problem looking at a few pictures of power brake setups. I purchased the dual diaphragm setup but decided against installing it because of clearance issues with the carb. With a V8 it wouldn't be a problem at all. I'll be staying with the stock power brake setup and with a new booster and MC I think it will work fairly well.
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Unread 09-05-2012, 02:10 PM   #10
toadman81
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Quote:
Originally Posted by Mickey_Mouse View Post
If you have a V8 and had the dual booster, you would have no problem. I bought a booster similar to that in pricing, it wouldnt fit on the brake pedal, the pushrod was different, and very little clearance between the booster and the carb, I had upgraded to a motorcraft 2100. I returned it for a OEM unit, power brakes and master cylinder.

http://shop.advanceautoparts.com/web...m=power+brakes

this thread has a conversion using a vans braking system for added stopping power.

http://www.polyperformance.com/shop/...YJ-p-1567.html

http://www.pirate4x4.com/tech/billav...s/#Vancoreview
decided to go the OEM route since the local parts store has it in stock and it's only a few bucks more than getting just a new master cylinder. hopefully this fixes things, but if not, I'll be reposting tonight. thanks for all the info!
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Unread 09-05-2012, 03:21 PM   #11
scooter71954
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I would check the vacuum line from the manifold to the booster. Also check the fitting on the booster where the vacuum line attaches. they are prone to cracking.
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Unread 09-05-2012, 08:14 PM   #12
toadman81
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Quote:
Originally Posted by scooter71954
I would check the vacuum line from the manifold to the booster. Also check the fitting on the booster where the vacuum line attaches. they are prone to cracking.
That vacuum line was shot, not to mention the fitting on the booster was cracked. Master cylinder was in terrible shape and had a good amount of corrosion. I believe both the booster and MC needed to be replaced. Glad I didn't splurge for the dual diaphram cause no way that would have fit with my weber carb. Gotta pickup a new vacuum line tomorrow and bleed the system and test her out. Will give an update. Can't tell y'all how much I appreciate the insight! Thanks!
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Unread 09-05-2012, 08:25 PM   #13
brownbagg
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power booster bad
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