Brake Leak - Need help identifying

[Redd]

Was looking at the brake reservoir today and noticed paint bubbling at the interface between the master cylinder and brake servo (red arrow). Suspect this is caused by brake fluid corroding the paint.

What I can't figure out is where the fluid is coming from. I also noted that:

- Brake fluid reservoir cover is wet with fluid, but the fluid container is dry
- Master cylinder body appears to be dry/clean
- Fluid was changed 3 months ago
- No noticeable fluid loss

Any idea where the fluid could have come from? Mech says it might be past fluid overfill leaking down. But I'm not buying it cos the paint is only bubbling at the joint area, which suggests that the fluid is originating from the joint. Every where else is clean/dry.

I was at track 2 days ago and also noticed that my brake pedal would go soft at early sessions. Early enough that it should not be fluid fade or pad fade. It's almost as if pressure is somehow leaking out. I'm on Endless RF650 fluid and Pmu HC+ pads with Brembo GT bbk, if that helps.

Any ideas?

[WingZeroX5]

Did you overfill?

[Redd]

Originally Posted by WingZeroX5

Did you overfill?

Fluid level is below minimum mark.

[nycplumber]

Any resolution to this?

[Redd]

Originally Posted by nycplumber

Any resolution to this?

Yes this was fixed ages ago. Turns out it was the o-ring between the master cylinder and servo. Replaced that and it has been good since.

[nycplumber]

Awesome and that leak didn't ruin your brake booster?

[Redd]

Originally Posted by nycplumber

Awesome and that leak didn't ruin your brake booster?

Brake booster was fine. Just the paint was peeling where brake fluid had leaked out. Cleaned it and resprayed it black. All good.

[nycplumber]

That's great. Strange because fluid should never touch that oring

[Redd]

Originally Posted by nycplumber

That's great. Strange because fluid should never touch that oring

Maybe just a bad o-ring or not properly tightened. Replaced it and never happened again.