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Master Cylinder Bad?

LowTech

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Arizona
So if we're going w/ the cup being swollen I'm interested in how that happened.
This is an MC that has been in use (though I have been having issues w/ it),
has had dot 5 always,
I took it apart and did have to push it out from the other end (but not w/ a lot of effort if I remember correctly),
and it was out in the desert air for about a week before I put it back together.
Could this have occurred while it was in use? Or from being in the open air? Or from brake cleaner getting on it?
I'd like to avoid it happening in the future if possible.
 

WillWagner

The Person You Were Warned About As A Child
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Swollen or hardened. Could be the V seal too. A rebuild kit is inexpensive, under $30 for one with a spring. Look up a rebuild kit for a FE777 master cylinder. Get a kit with a spring and check valve. try and avoid ChiCom made kits, the rubber in them is junk. NAPA can get them.
 

LowTech

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Location
Arizona
Thanks, and I have a rebuild kit from Big Mike that I've been holding on to and was hoping since the parts all looked good I could continue to save it for an emergency.
I'll use it to replace the parts I put back in. It would be nice if I could pick up just the rubber bits and keep them w/ the "not bad" parts that I have for a future use, "if needed".

Still interested in what could make them swell.
 

Jeepsinker

Well-known member
5,399
454
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Location
Dry Creek, Louisiana
So if we're going w/ the cup being swollen I'm interested in how that happened.
This is an MC that has been in use (though I have been having issues w/ it),
has had dot 5 always,
I took it apart and did have to push it out from the other end (but not w/ a lot of effort if I remember correctly),
and it was out in the desert air for about a week before I put it back together.
Could this have occurred while it was in use? Or from being in the open air? Or from brake cleaner getting on it?
I'd like to avoid it happening in the future if possible.
I'd say most likely from the brake cleaner. It's hard on a lot of different plastics and rubber compounds.
 

WillWagner

The Person You Were Warned About As A Child
Super Moderator
Steel Soldiers Supporter
8,518
2,698
113
Location
Monrovia, Ca.
Thanks, and I have a rebuild kit from Big Mike that I've been holding on to and was hoping since the parts all looked good I could continue to save it for an emergency.
I'll use it to replace the parts I put back in. It would be nice if I could pick up just the rubber bits and keep them w/ the "not bad" parts that I have for a future use, "if needed".

Still interested in what could make them swell.
You can buy cups alone. I have never tried to remove the seal on the piston. Also, brake fluid isn't a lubricant so it will not make the components slippery. Every MC or wheel cylinder I have built, I have used a product called McKays Brake Cylinder Assy Lube. Never had an issue, I use it for MC's and wheel cylinders we put into service or for the ones that are on the shelf for a faster repair.

I tried looking for the exact stuff, but me thinks they are out of business, however, I did find the same stuff just from a different manufacturer,

 

LowTech

Active member
Steel Soldiers Supporter
971
151
43
Location
Arizona
The new parts went in smoothly and functioned as expected. Bled everything out to new purple and only the MC to slave cylinder showed any sign of crud. I did have to remove everyone of the bleeder valves and clean them out first as there's a little wasp that loves to fill them up w/ clay after laying eggs in them.🙄
Not sure how everyone else is doing it but when it comes to getting the rubber boot back on the front of the MC I ended up turning it inside out back about a pleat or so and then rolling it onto the MC. I did have it on the pushrod first.

Now I just need to adjust the brake shoes as I have too much pedal before the shoes start touching.
 

Mullaney

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The new parts went in smoothly and functioned as expected. Bled everything out to new purple and only the MC to slave cylinder showed any sign of crud. I did have to remove everyone of the bleeder valves and clean them out first as there's a little wasp that loves to fill them up w/ clay after laying eggs in them.🙄
Not sure how everyone else is doing it but when it comes to getting the rubber boot back on the front of the MC I ended up turning it inside out back about a pleat or so and then rolling it onto the MC. I did have it on the pushrod first.

Now I just need to adjust the brake shoes as I have too much pedal before the shoes start touching.
.
You can eliminate the wasp laying eggs and plugging up your bleeder screws. There is an assortment pack and there is a #10 cap that will fit over the end of your bleeders @ Home Depot and other assorted hardware stores.

1722616927601.png

You also need to consider keeping the breather caps on your differentials unplugged.
Especially since you have the little varmits trying to plug your bleeders...

.
 

LowTech

Active member
Steel Soldiers Supporter
971
151
43
Location
Arizona
.
You can eliminate the wasp laying eggs and plugging up your bleeder screws. There is an assortment pack and there is a #10 cap that will fit over the end of your bleeders @ Home Depot and other assorted hardware stores.

View attachment 928923

You also need to consider keeping the breather caps on your differentials unplugged.
Especially since you have the little varmits trying to plug your bleeders...

.
Excellent! I was going to start researching just such a cap!
 

GunInstructordotcom

Active member
96
112
33
Location
Castella, California
The new parts went in smoothly and functioned as expected. Bled everything out to new purple and only the MC to slave cylinder showed any sign of crud. I did have to remove everyone of the bleeder valves and clean them out first as there's a little wasp that loves to fill them up w/ clay after laying eggs in them.🙄
Not sure how everyone else is doing it but when it comes to getting the rubber boot back on the front of the MC I ended up turning it inside out back about a pleat or so and then rolling it onto the MC. I did have it on the pushrod first.

Now I just need to adjust the brake shoes as I have too much pedal before the shoes start touching.
Regarding the boot on the front of the MC, I tried and tried to pop it on myself. Every time I would get half on and try to pop the other half on, the first half would pop off. So I had my wife from up top and I popped the lower half on from the underside. When she tried, it popped right on from up top.
 

GopherHill

Well-known member
474
1,250
93
Location
Thomaston, TX
You can buy cups alone. I have never tried to remove the seal on the piston. Also, brake fluid isn't a lubricant so it will not make the components slippery. Every MC or wheel cylinder I have built, I have used a product called McKays Brake Cylinder Assy Lube. Never had an issue, I use it for MC's and wheel cylinders we put into service or for the ones that are on the shelf for a faster repair.

I tried looking for the exact stuff, but me thinks they are out of business, however, I did find the same stuff just from a different manufacturer,

I got my brake assembly lubricant from Euromotor Electric.
 

GunInstructordotcom

Active member
96
112
33
Location
Castella, California
I had something unexpected happen today. I was gravity bleeding the top of the airpack after replacing the master cylinder. I loosened the bleeder and heard a momentary hiss of air in the clear bleeder tube I was using. A small amount of fluid came out and then nothing. After a few minutes, I slightly, gently pressed the master cylinder pedal lever and fluid with bubbles came out, then solid fluid trickled out. My old MC was dry so I guess I should not be surprised that the airpack had no fluid in it. After I finished, the remote reservoir was down about an inch.
 
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