This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Front Brake Air Leak

Joined May 2009
279 Posts | 0+
Hi guys,

Within a week of having my RSV bike I boiled the brake fluid at Mallory Park and had the lever coming back to the bars.

Under the advice of the forum I bled the brake fully and replenished it with the expensive Silkolene Pro Race fluid.

I got lever travel to zip with no air in there, but after hard riding it always seems to get a few bubbles in it. We're not talking everytime, but maybe after 2 weekends of riding? (200 miles perhaps?)

Usually I just bungee the cord back and crack the nipple to let them out, then it's fine but I know this isn't ideal practice.

What's the cause? Is it old hoses, leaky master cylinder, leaky caliper seals or something altogether different?

It's an 03 Mille with non-radial 4 pots and I'd like to cure this over the winter if possible.

Cheers!

J
 
I have similar problems i have to bleed the system after a good thrash but cannot find any leaks?. I was told i its down to inccorect bleeding but ive been doing this for 10 years without any problems until i got this bike, would it be worth biting the bullet and changing the master cylinder/hoses?
 
I had the same problems, ended up changing the master cylinder for a brembo radial, it's a bit sharp on the road but blinding on track.
 
So it's more likely to be master cylinder than caliper then?

Ahh....

What levers/master cylinders would be compatible then? I might have to start scouring through flea-bay...

Or is that flalse economy and you should buy new?
 
I`m sure you could just buy a re-build kit for the master cylinder. Also , put all new copper washers on the banjo fittings and take out the bleed nipples and wrap the threads in PTFE tape to seal them properly.
 
I've been bleeding the rear caliper and used a pressure pump to draw the fluid through, but even with the bleed nipple tightened there was still a pressure loss showing on the guage. I wound some ptfe tape around the nipple (points for the most uses of the word nipple) and no pressure drop and it seems fine for now.

Not conclusive in your case but worth checking.
 
Sounds like we have a plan then!

I'll buy another bottle of brake fluid, some ptfe tape and washers.

Hours of fun....

Cheers guys.
 
×

New Posts