Master Cylinder Geysers Brake Fluid?

[Guest]

Thanks to Brendan, JT, and tkent for hounding me on checking my brakes because boy were they nasty. One of the front brake lines was clogged, meaning only one of the double discs was doing anything. It took a lot of poking around with a paper clip and then some compressed air but I was able to clear it.

The real issue is the front master cylinder. When I squeeze the brake, the crazy thing fires a stream of brake fluid up and out of the reservoir like a geyser. I'm guessing this means there's some kind of seal inside it that's shot? If so, would this be included in a rebuild kit or should I start shopping for a new MC?

At least the back brakes were fine.

[Nessism]

The geyser is normal and shows that the fluid return and feed passage is open.

Regarding the brakes in general, you should perform a full system tear down: calipers, master cylinder, and replace the lines. That sludge which plugged up the line suggests the entire system is contaminated. Failure to perform proper maintenance on the brake system can get you killed. Please tell us you are taking this seriously.

[eil]

+1 on the full rebuild (both MCs and all calipers) plus new stainless steel braided brakelines. There are oodles of threads on brake rebuilds, if you've read through them and have any specific questions, we're here to help.

[bwringer]

Yep, the geyser is normal.

Put the cap on, or don't yank the lever so fast.



But yeah, if things got so bad that a brake line clogged, there's a lot more evil gunk in there waiting to kill you. You have to take it all apart, rebuild with OEM parts, and replace the brake lines. No way I'd ride anywhere until it's sorted.

[Randomize]

Thanks, guys. Yes, rebuilding the brakes is now at the top of my to-do list.

Should I be concerned that the rear MC doesn't geyser or is it only the front one that typically does that? It blows my mind that it's normal for that to happen

[bwringer]

Thanks, guys. Yes, rebuilding the brakes is now at the top of my to-do list.

Should I be concerned that the rear MC doesn't geyser or is it only the front one that typically does that? It blows my mind that it's normal for that to happen

The rear uses a reservoir connected to the MC by a hose. So the port that makes the geyser is much more covered up.

[Brendan W]

Between the gear oil and the brakes you now have hard evidence of the state of this machine and everything is suspect. Make sure that at some stage you check every nut,screw,bolt and split pin from nose to tail bearing in mind that for some unknown reason handlebar clamps always get overlooked.