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thinking I have a bad master cylinder now.....

Austringer

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Atlanta, Ga
About a month ago I took the v to a car show about 2 miles from my place with no problem. One the way home it felt as though my brakes were starting to drag and my wife who followed me home said that the brake lights came on while in the neighborhood. When I parked in the driveway, turned her off, but left the service lights on, the brake lights stayed on. I figured the brakes were adjusted too tight so I went back and adjusted them per the manuals major adjustment.

Took her back out today and the brakes seemed to work fine for the first mile. I pulled into a friend's place for about 10 mins then started to back out. As I backed out, the master cylinder was very hard to push and I was getting reduced braking. Returning home, I basically had to stand on the brake pettle to get her to slowly come to a stop. When I got home, turned her off and , yep, brake lights were on and the brake drums were very hot. The brake light switch is located on the front of the master cylinder so I thought that line was more than likely under pressure. Went to the rear and cracked the blleder on the vacumm booster and brake fluid came out under some pressure. I checked the adjustment ( travel) in the brake petal and it seemed correct. The brake petal moved some again, but I didn't get back out to test. Based on the fact that the line going into the mc was pressurized, I'm thinking there is something not letting the fluid back into the MC, either something is blocking it or the piston is messed up. The mc appears to be a standard jeep mc, so I'm going to replace it tmw and see what happens. Hope it is just a mc that went bad. The vehicle had not been driven in about 10 years. I'm using DOT 5 brake fluid and all wheel cylinders and pads are new. Again, if the line to the master cylinder was pressurized, something is blocking it from getting back into the mc as it is open to atmospheric pressure. Will post on how it goes. Let me know if you have any suggestions.

Jason
 

poppop

Well-known member
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Location
Brooklet, Ga
I have had the return hole in the master cylinder plug and prevent the fluid from returning on a couple old farm trucks. Had to loosen a bleed line to release brakes to make it home. On my M51 dump the push rod was to long and prevented the piston from returning all the way and kept the return hole covered up.
 
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B3.3T

Well-known member
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Location
SW Ohio
Sounds like piston sticking. Cheap enough to replace. Swap it out and be done with it.
 

Austringer

Active member
Steel Soldiers Supporter
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28
Location
Atlanta, Ga
Problem is finding one that not going to take a week to get in or longer. No one has one in the area.

Jason
 

Austringer

Active member
Steel Soldiers Supporter
410
34
28
Location
Atlanta, Ga
Turns out it, it was the vacuum booster had gone bad, put a new one it today and she stops like a champ now.
Jason
 

M813rc

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Near Austin, Texas
The vacuum booster was a source of headaches for me. Mine, which was new at the start of the restoration, gave up rather quickly, but caused odd symptoms. Just replaced it again, works good now. Your V should be able to easily lock up the tires when its all working properly.

Watch for even small spills of Dot-5 on the drivers side floor in the V, because getting it on your boot soles can cause great excitement when you hit that metal brake pedal!

Cheers
 
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