Leaking brake fluid to master cylinder and cannot stop it

I was trying to bleed my brakes and it keeps leaking fluid from near the brake master cylinder. I investigate and find that it is the connection in the picture that goes from the reservoir into the master. No matter what I try this banjo bolt keeps leaking. I had Copper washers, Then I tried fiber washers, then I used two fiber washers between the banjo and the master cylinder and it still oozing. I was wondering if any of you guys had any ideas. Thanks again for any input it is much appreciated.

Do you mean it leaks under gravity fluid pressure from the reservoir or when you apply pressure to the system?

Are you using a vacuum bleeder? Pressure bleeder at the reservoir? Or just traditional pedal pressure?

It leaks without any pressure from the brake pedal Or while bleeding. Just the pressure from the fluid coming from the reservoir makes it leak

I would suggest to take the banjo out and inspect all seating surfaces and the washers. There may be a hairline crack in one of the two washer or the banjo or the bolt. The tube you are using from reservoir to Master is not standard. It may have some sort of defect like a split. Assuming it is brake fluid compatible, I would cut off the last inch of it and use fresh tube to press onto the Banjo
Dennis 69 OTS

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I used those plastic hoses because I’m using silicone brake fluid. The banjo bolt and the master cylinder are new so the surfaces are defect free.

I’d suggest going back to copper washers, one per side of the banjo, but this time try heating them cherry red hot before installing.

Thanks, will give that a try

But letting them cool down first, just sayin :slight_smile:

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Good point, but even with my map gas couldn’t get it to glow red

That seems odd - pretty sure I have got them glowing red with just a propane torch.

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I melted a few with propane. Ten seconds tops. You can make steel glow too, easily, so something is wrong.

Are you sure it’s leaking at the banjo and not at the barb? The angle of the hose; maybe the hose is too stiff to seal that and it looks as if it leaked elsewhere (I‘d try an injection hose clamp).

And once you have annealed the washers clean them up on a wire wheel and then do the banjo up really tight.

Try your gas stove if you have one. You should be able to get them hot with just an air/gas torch. You should certainly not need oxy/gas. As above you will just end up with blobs of copper if you use that.

The fitting you are looking at is just the filler from the reservoir. All it does is let fluid enter the master cylinder and so there should be no pressure on it at all. If you are getting pressure leaks when you push on the pedal there may be a problem with your master cylinder.

I note you have clear hose going to the banjo. Is this just to do the bleeding? If not you would need to ensure it is suitable for the silicone brake fluid. If not you should be using an appropriate hose that is safe for the fluid.

What hose do you guys usually use? Maybe I Will change them just to be sure. Thank God I’m using silicone or there be no paint left in the engine compartment. I think I will go out tomorrow and buy a new torch.

I’m using the stock hose (original actually) from the reservoir to the master - that is with DOT5.

I also use the original clamps which are similar to the fuel injection clamps David mentioned.

For some reason I reused the banjo fitting from the old master on the new replacement. Cannot recall why, maybe I just liked the look of it.

I will go to the auto parts place tomorrow when I’m buying a new torch, and buy some brake hoses is the inside diameter 3/8? Thank you. Now I have to make a new post for a new issue.

Yes, 3/8" ID…

Thank you very much.

Probably for the same reason I did. My replacement master cylinder had different types of fittings on it than the original. The reservoir connection on the new cylinder wasn’t a banjo. So, I switched out the fittings from my old cylinder to avoid changes to hose runs etc.

Hello, I had the same problem, I used Stat-o-seal and now it not leaking anymore, I tried both aluminum and copper but that didn’t work.

The problem with using Stat-O-Seal is that one must confirm that the rubber used on the inner lip of the seal is compatible with brake fluid. Regular O-rings are not compatible with brake fluid. I dunno what elasomers are used on the Stat-O-Seal, but it wouldn’t surprise me if it’s the same stuff as an O-ring. I’d want to drop a Stat-O-Seal in a little jar of brake fluid and leave it for a few weeks before I trusted it on a brake system.