Master Cylinder Rebuild

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#1
Rebuilt the master cylinder on the Overlander. When I unloaded it from the trailer I used to take it to the VIN inspection it lost all brakes. Just rolled across the yard until it decided to stop. Good thing it stopped when it did, as I had about 10 more feet and I would have had to decide either take out the iron fence around the pool or my shed over my well.

I decided to rebuild instead of replaced due to the unique master cylinder it has.

CEB7560F-9931-48C6-88D3-71CA54DD8472.jpeg

It has these glass bowls set in the side for fluid level check. I have never seen that before.

I taped it off, sand blasted the exterior, painted with Eastwood brake silver. Then pulled the old plungers. They were stuck as stuck could be. Had to plug the interior holes, and shoot compressed air into the brake line ports. Finally the plungers dislodged and shot out.

66BB824F-2758-49D1-A65C-3C260F721DAC.jpeg

Fairly certain the nicks in the o rings are what caused the loss of brakes.

809A9F4D-EA7D-4570-834D-F062897BB813.jpeg

If you look at the top one, you will notice a chunk missing from the o ring.

The bore looked good, so now I just need to bleed the brakes and adjust them.

One step closer to an inspection so I can get it licensed. Yeh!
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#3
I was searching the net for 258 engine accessory brackets for ac compressors and found a parts catalog.

291519B6-AEC8-4366-B388-C293D540EC51.png

Interesting that the export brake master cylinders for economic commission of Europe and Australian Design Rules use a sight glass. I have tried to locate these, but so far have not found a source for the export spec master cylinder. I contacted a shop in Australia and they have not seen one with the sight glass. Odd.

7459001A-4798-4580-8447-2F18A1560A40.png
 
City
Halifax
State
UK
#4
I live in the UK and have seen them on full size Jeeps and J series pickups but i cant remember ever seeing one on a CJ i am going to have to look at them all now thanks!...
Now this may be because of the age of these cylinders they have all been swapped out for newer units with no sights fitted.
Im sure on the ones i have seen you cannot tell if there is fluid in there or not though as the glass or plastic whatever looks to have a tendency to cloud up which would make it kind of pointless.
I am off to see if any of the old masters i have had the sight glasses now will report back!
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#5
I live in the UK and have seen them on full size Jeeps and J series pickups but i cant remember ever seeing one on a CJ i am going to have to look at them all now thanks!...
Now this may be because of the age of these cylinders they have all been swapped out for newer units with no sights fitted.
Im sure on the ones i have seen you cannot tell if there is fluid in there or not though as the glass or plastic whatever looks to have a tendency to cloud up which would make it kind of pointless.
I am off to see if any of the old masters i have had the sight glasses now will report back!
If you come across any and are willing to sell one let me know. I’d love to have a spare on the shelf. I’m trying to keep this thing as OEM as possible (or at least make it look as OEM as can be done).
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#6
I have been fighting the bleeding of the rear brakes ever since replacing the master cylinder. Fronts bleed great, but the rear, not so much. I am getting no fluid from the rear on either side. I am using a vacuum bleeder, and I got all the old green fluid out, but no new clear fluid is coming out. I have tried pedal bleeding, gravity, vaccum and nothing. I have pushed the front button in on the multifunction brake valve. Tried centering the valve from the brake light switch port, nothing. The brake light is not illuminated, which leads me to believe the valve is not cutting off the rear fluid, but :shrug:

I plan to brake the lines loose from the MC to the valve to ensure I have fluid flow there, then from the valve to the rear axle to ensure flow there.

Any other suggestions? I am just :banghead: right now. Also spun the bottom center nut in the frame holding the valve on. That will be fun getting that loose to replace the valve if necessary. :banghead: :banghead: :banghead: Probably will require cutting the bolt head off and driving the nut and bolt out thru the frame. :banghead: :banghead: :banghead:

Grrr.

Wife is bugging me to get this thing registered so she can start driving it! Gotta get the brakes done and get the a/c installed. (And floor boards replaced, tranny leak plugged, fuel injection installed, and...) :cheers:
 

jammer1

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Maple Hts.
State
Oh
#7
Sounds like the proportionate valve may be clogged (portion going to rear brakes). I was thinking along the same line as you. Loosen the rear brake line (from M/C at the valve) and see if you can get it to bleed at the in part of the valve. If that works try loosening the brake line at the rear of the valve to see if flows through the valve. If that works steel brake line that goes into the block end of the rubber line. It is possible that the rubber hose is damaged and blocking the flow to the rear. Even with air in the system you should get something out of the rear bleeder screws (gravity or vacuum pump bleeding).
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#8
I finally got back to working on this. Bought a replacement multi valve, but it is different.

1F805185-C4C4-4D86-8758-F3DFB8A8D384.jpeg

The switch is a different size. Looks to be a Chevy type valve to me, but all the ones jilted for a cj have the same larger switch port. Unfortunately the switch connector is different too.

I ran the old switch through 5he parts cleaner and got all kinds of gunk out.

So the plan is to steal the valve off my 82 and use on the 83.

But I will need a replacement for the 82. So the question is, is the yj valve the correct one? From the web store images, the yj one appears to have the correct switch?
 

jammer1

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Maple Hts.
State
Oh
#9
I don't have the wiring diagram at home but if I remember right the stock switch has 2 wires on it. One wire is from a ground source (ignition switch). It runs to the proportionate switch. The other wire from the switch runs to the brake light (the ground wire to supply the ground to the light). The parking brake also has a switch. When the parking brake is engaged, it supplies a ground that ties into the wire going to the brake light switch. On the 1 wire switch, the ground comes from the proportionate valve itself. You need to attach that wire to the wire that runs to the brake light. The hardest part is which wire. My diagram at home lists both wires as black. Keep the correct valve with the right valve. Any difference and you take a chance of a leak.
 

Mancunian

Basic User
CJ-8.com Member
City
Bridgeport
State
WV
#10
Last edited:

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#12
The Mopar part JEP52009114 appears to have the correct switch with 2 wires.

0A654FA4-2E12-479E-B80B-724A28C0F9F1.jpeg

This is supposed to be a YJ part, but looks like a CJ part, just not sure if the picture is correct.

I am fairly certain that I can combine the 2 wires and use the single pin switch, but would rather keep it more original. Reason I am confident the wires can be combined is how the stock switch works.

8FE71FE4-15CE-4258-9F22-4A54B717DBA4.jpeg

This is my stock switch, there is a single pin that shorts to the valve, on the other side in the connector it splits into 2 pins that are connected by a wire to the switch pin. Basically, both wires are fed the same ground feed but the split is in the switch. Kinda hard to see, but the shiny part is the wire connecting the 2 pins to the switch pin in the center.

44A4E7E5-82E9-4E53-B7A6-5FC041299625.jpeg

This is also a YJ valve, but does not look like the one from the JEP52009114 part number.

Might run by a dealer tomorrow to see if they can get the Mopar part. :shrug::shrug:
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#13
Went by a local dealer, and that part number crosses to the bottom photo. I went ahead and ordered one from a seller on amazon. Fingers crossed that it will be right, but I have serious doubts. Looks like my options are to rebuild, get a used one, or change the switch.

For now, I'll just use the one from my '82 on the '83. Guess I'll figure out what to do on the '82 when I get to that point in the build.
 

jammer1

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Maple Hts.
State
Oh
#14
The single wire valve works fine. It's also used on many of the M/C, power booster kits that are sold.
 

ag4ever

Average Nut
LIFETIME
CJ-8.com Member
City
Richmond
State
TX
#15
The mopar 52009114 is definitely not the right one. Correct switch, but wrong body.

20191112_070311.jpg

20191112_070242.jpg

Gotta return this one now. Oh well, it appears this is one more part that is no longer available, and a similar aftermarket part must be made to work.

I'm gonna use my original from the 82 on the 83, and use the new one with a new wire harness on the 82.
 
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