CJ 7 Brake Master Cylinder

Anybody????

Also more info.... In the near future I will be swapping in a rear Dana44 from a 74 CJ5, which has 11" rear drums instead of my current 10.75" drums on the AMC

1. Should I go ahead and get the MC from a 74? But the 74 was designed for fr> During wheeling Saturday I lost my brakes in my '79 CJ7, haven't had

My guess is the rim and rubber seal on the fluid container are dirty letting it leak out the top.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

aGraham wrote:

There has been fluid leaking around the firewall since I bought it, that is what make me think the seal finally died.

What do you think about the difference when I change the rear axle to a Dana 44? Will I need a different MC?

I started looking at it tonight, looks like it is leaking around/at the proportioning valve. Looks like I am going to have to possibly replace the valve and some of the lines. The lines look really rusted so I am sure they are not going to unscrew easily. It is definitely leaking from both resevoirs so I am assuming the valve is bad. I could not pin point the leak because I was working by myself, had to pump the brake pedal a bunch of times to get pressure, but then before I could lay down and slide underneath it was just running down. I could hear it spraying as I was pumping the pedal.

To replace the lines, should I replace the complete lines or can i just splice in new parts?

I have a mechanic buddy who is going to help me, he says he has a flaring tool and everything needed.

I don't think you will need anything different.

The proportioning valve goes by PSI not volume and the wheel cylinders don't move any more because of a physically bigger drum, the movement is in the gap or adjustment.

A leak out the cover seal can/does run down onto the firewall on the engine side. Blown seals leak down the firewall on the inside and soak the carpet.

Having that rubber gasket get rust flakes and leak is pretty common. My CJ7 was like that and I got air in even on it's first off road run after the frame up rebuild. I didn't clean that part and got dinged for it. Had to bleed the whole system way out in the bush....

Mike

aGraham wrote:

Well after four trips to town, and almost 8 hours my CJ now has the best brakes since I have owned it. 3 separate trips for lines then a trip to his shop for his flaring tool to change the fittings on 2 of the lines. My buddy & I ended up having to replace 4 out of 5 of the brake lines. I think mud or a stick must have gotten lodged in there and tweaked the proportioning valve, almost pulling it off of the frame, which caused the 25 year old lines to crack. It looks like the one brake line we did not have to replace had been replaced in the past. 

Also we found that the brake lines are possibly hooked up wrong. My buddy said that usually the front brakes are controlled by the rear resevoir of the Master Cylinder and vice versa. My Jeep is set up with the front resevoir controlling the front brakes. Is this right or wrong? The brakes seem to work great so we left it the way it was.

We also found a quarter sized hole in the front section of the eqhaust pipe. After replacing that and the pipe to manifold donut gasket my Jeep is so quiet I had a hard time driving it home. It is hard to drive a loud vehicle for 2 years and then try to shift it when you can't hear the motor!!

I found a sketch I drew of the proportioning valve hookups when I pulled my `79 CJ-5 apart, this may or may not help you. Looking at the valve body as though your head was where the bell housing is and the valve is mounted to the inner left frame rail, the connection that exits to the rear goes to the rear brakes. Then working clockwise, the next connection (top side, to the rear) goes to the front connection on the master cylinder. Next is the warning light connection, then the connection to the rear port on the master. Exiting diagonally to the upper front is the right front brake line, then on the lower right is the left front brake line.

On factory-made lines the flair nuts connecting the valve to the master are different sizes to prevent bass-ackwards hookups.

By the way, it might not have been a stick that yoinked your valve off. You should check that part of the frame for rust.