My brake issues -
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post #1 of 5 Old 03-30-2004, 09:33 AM Thread Starter
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1981 CJ7 
Join Date: Jan 2004
Location: Valley Forge, PA
Posts: 47
My brake issues

I see that someone else on the board has an open thread about brake issues right now too, but I didn't want to step on his question. So if you're reading this and like, know stuff about brakes, look around the list a little more and see if you can help the other member, too, please.

Ok, my problem: sometimes (it's happened 2 or 3 times now) while stopped at an intersection or wherever with my foot on the brakes, the pedal -- normally very firm -- will suddenly get a little soft and sink about halfway to the floor. Then it stops, and the brakes hold. But the parking brake warning lamp comes on, which I guess is my CJ's way of saying "yo, brake problem." Pump the pedal even once, and all is back to normal.

It's an 81 CJ-7 with power brakes, and I just had them checked out for my annual state inspection. My mechanic couldn't find anything wrong, no leaks or anything. Since the problem doesn't happen all the time, I don't really know what to try next. Could the power brake booster be failing? Is there any way to check that out for sure before replacing it?

Thanks in advance!

'81 CJ-7, 175,000 miles
Stock 258, SR-4
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post #2 of 5 Old 03-30-2004, 09:43 AM
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1971 CJ5 
Join Date: Jan 2002
Location: Eagle Point
Posts: 7,283
Master cylinder is going bad. There is probably some grit or buildup in the front half of the cylinder, lifting the cup and allowing it to loose pressure. Pumping the brakes will "recharge" that half of the system, restoring the pedal.This inbalance of pressure will trip the brake warning light telling you there is a problem.
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post #3 of 5 Old 03-30-2004, 10:12 AM Thread Starter
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1981 CJ7 
Join Date: Jan 2004
Location: Valley Forge, PA
Posts: 47
Hmm, okay, that sounds serious. Perhaps a pre-emptive master cylinder replacement would be a good idea.


'81 CJ-7, 175,000 miles
Stock 258, SR-4
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post #4 of 5 Old 03-30-2004, 03:04 PM
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Location: Richmond, VA
Posts: 2,226
Ebay one if you want..

85 CJ7 / 258 / T176 / Dana 30/ AMC 20

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post #5 of 5 Old 03-31-2004, 09:26 AM Thread Starter
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1981 CJ7 
Join Date: Jan 2004
Location: Valley Forge, PA
Posts: 47
Originally Posted by Geer_hed
Ebay one if you want..
Thanks -- missed that one (not sure if it would have fit anyway).

But I also just recently discovered the dangerously convenient fact that Quadratec is located about 15 minutes from my house, so I can buy stuff and not have to pay any shipping. That's either cool, or really bad.

'81 CJ-7, 175,000 miles
Stock 258, SR-4
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