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Front brake master cyclinder

  • Thread starter Thread starter Guest
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So if you push the shaft inwards, what do you see ?

Just the shaft moving inside a metal ring, or also the thicker part of
the shaft going in and out ?
 
Rijko said:
So if you push the shaft inwards, what do you see ?

Just the shaft moving inside a metal ring, or also the thicker part of
the shaft going in and out ?
Click to expand...

I see a metal shaft, but it doesn't move, even when I move the piston. And I already removed the circlip, the washer, and the rubber gasket.
 
That's an obstruction that should not be there,
probably the metal ring/washer.

If you wiggle the end of the shaft of the piston, can you
get that metal thing to move ?
 
Yes, the circlip groove is visible. I look down into the piston hole, and there still seems to be a but of metal holding it in, but I think this is part of the piston itself. There's nothing else down the piston shaft that seems to be holding it in. It wiggles a bit, but won't come out.
 
ZombiePotatoSalad said:
Here it is with the circlip, washer, and gasket removed. I haven't been able to get the piston out.View attachment 59956
Click to expand...

Can you post another picture of the inside ?
In this picture i think i still see a circlip and gasket.

Has every other bolt/screw been removed like on the inside of the fluid reservoir ?
Maybe someone used way too long bolts and one is sticking inside the piston
shaft, blocking the way out for the piston.
 
Rijko said:
Can you post another picture of the inside ?
In this picture i think i still see a circlip and gasket.

Has every other bolt/screw been removed like on the inside of the fluid reservoir ?
Maybe someone used way too long bolts and one is sticking inside the piston
shaft, blocking the way out for the piston.
Click to expand...

Here's another picture. There's nothing inside but the piston.
15788148211187736404687809342882.jpg
 
thanks. First thing is to get the old rubber out.
It blocks the view of the possible cause the piston won't come out.

Use a screwdriver, pliers, heat it .. whatever it takes.
 
Get the remains of the rubber boot out.

Push the piston into the bore as far as possible.

You'll now see a washer that was between the circlip (that you've already removed) and the piston. This washer will have corroded/cold-welded to the wall of the cylinder. Use heat, penetrating oil, and some force to break it away. It doesn't sit in a groove. Don't get carried away and damage the cylinder wall!
 
Rijko said:
thanks. First thing is to get the old rubber out.
It blocks the view of the possible cause the piston won't come out.

Use a screwdriver, pliers, heat it .. whatever it takes.
Click to expand...

I have. The dust cover is out, as well as the circlip, washer, and rubber ring. All that came out.
 
Check again. I clearly see the remains of the rubber boot in the picture.

Not a rubber ring, a large boot and in the picture most or all is still in there.
 
OK good. Like Steve said, there probably is a washer corroded to the cylinder wall.
Can you now see that washer ?
 
The washer has been removed as well.
The circlip, washer, and rubber boot ring are all out. It's just the piston in there now. There's just a metal ring, with a depression within that, and the piston in the center.
 
That's it, I'm drilling the darn thing out. If it breaks, oh well. The plunger is wedged again, so I have to remove the whole plunger assembly by force. I'm trying to drill through the metal ring that's in there, but it's thicker than a washer.
As I stated, if you look at the plunger, it appears to be surrounded by another metal ring that appears fused to the plunger hole walls, yet no amount of banging on it with a screwdriver and hammer will remove it. In the video, the plunger seemed to knock against that. It's an Aisin master cylinder with a number 14 on the bottom. Did this model of master cylinder have a fused plunger assembly, like it was stuck fast to the body? It seems like they're one whole unit, not meant to be separated.

I'd like to keep the original look, but if I can't remove this plunger, I'll have to go aftermarket, which includes finding a way to make the taillight work again (I'll need someone to explain that to me).

EDIT: After pounding on it with a bigger hammer and screwdriver, the plunger assembly seems to have recessed further into the body. It shows it can move, but it went in the wrong direction.
 
Last edited:
Wow!

You're still at it?

I forgot to mention...I let the MC unit sit in a tank of clear solvent for 2-3 days which probably loosened the plunger from the sidewalls.

You can see a pic in my thread of the basket I used to dip into the solvent tank.

Continued patience and perseverance.

Ed
 
Yeah. What was the fluid you used? I've got some Liquid Wrench and WD-40.
 
ZombiePotatoSalad said:
Yeah. What was the fluid you used? I've got some Liquid Wrench and WD-40.
Click to expand...

I was on an Air Force installation...Holloman AFB, Alamogordo NM. I was able to use this huge tank where aircraft parts are soaked/cleaned. Looks like water but it's not good to stick your hands in there without rubber gloves.

Caliper2_zpse505f5f3.jpg


Ed
 
Yeah, I think it's utterly borked. The piston assembly isn't coming out, so I may just have to replace it.
 
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