'02 brake fluid change- frequency

[BSL]

Hey, just wondering what others experience with thier front brakes...

I have to change my fluid more often than my engine oil! The brake handle is consistently lower than I like, when I flush some new fluid thru, it gets better but never 'really good'. There is always about 1/2" free play.

Is this normal for Nissin brakes?
Im looking at getting stainless lines, but Im wondering if I really need a new master cylinder?

[ridelikeaturtle]

I'd say the braided lines should make a difference; dunno that you need a new mc. You shouldn't have to replace the fluid more than once a year.

[BSL]

Wow, once a year.
After about 2000kms my lever gets all soft feeling. I don't get any air out of the system, but the fresh fluid (DOT 4) makes a HUGE difference. Maybe its the kind of riding Im doing..

Anyone else?

[ridelikeaturtle]

ONLY 2000KMS???!!! Something's not right there. I'd suspect there's some air either trapped in the system, or it's getting in somehow.

Have you tried tying back the lever w/a strap and leaving it overnight? Maybe that'd force any air out.

[BSL]

I (finally) got a net set of seals and a piston for the master. Kawi parts. Ill update if it fixed the problem when I get around to swapping them out.

[fast911ray]

I think you'll find the problem is trapped air. Using a MightyVac will purge all remaining air in a matter of minutes. Just follow the simple instructions supplied.

[BSL]

I rebuilt the front master cylinder.
Didnt fix it tho. I found one of the caliper pistons to be sticking in its bore, just a little.
It moves and is hard to see, but it doesnt start moving until the other pistons are all the way out.

Caliper rebuilt kit is on order.

Now my back brake doesnt work!!
Seems the master is faulty, the lever goes all the way down with zero braking unless I pump it up. No leaks.

[fast911ray]

BSL..I dont think either master is bad. The rear is almost impossible to bleed without a vacum bleed tool...similarly for the front. It's rare for a master to go bad, really...if you do go on to replace it, I think you'll find the problem remains. A simple test..once you pump and develop pressure, does the lever remain relatively firm, or sink as it loses pressure? If it sinks rapidly, there is a probability it's bad..but if it remains firm or sinks slowly it's probably as I suggested, trapped air. Either way, before investing money in possibly unnecessary parts, why not borrow or buy a bleedtool... something you'll need at some point anyway.

The same goesfor the caliper...if anything, a sluggish piston will raise pressure not cause it to drop. If it's not leaking fluid then I doubt you'll find any benifit from replacing seals or pistons. Again, using a vacum bleeded will provide the answer to all questions and probably be the solution for the problems your'e experiencing.

Why am I so positive? Because I've been down the same road before. Got the same advice but ignored it[ naturally]...sad to report, after replacing many $$$ of unneeded parts, I bougt a 'MightVac'... never had a problem again...that was some 30 years ago.

[fast911ray]

Oh..to answer the original question: brake fluid..if not silicon..should be flushed every two years at the longest..reason being, it absorbs humidity from the atmosphere, over time becoming contaminated with water.This water then sets about eroding cylinder bores and destroying rubber seals. In exremely humid enviroments fluid should be flushed yearly Silcon fluid is non-hydroscopic so will not absorb moisture from the air and is consideed 'lifetime'.

My personal favourite is ATE 'Blue' ,with AP600 or Motul 600 close behind. My reason for choosing the ATE Blue is it's blue colour..which makes it easier to determine when all old fluid has been flushed and the system filled with fresh. Typically I alternate between ATE Blue and one of the other brands..again because of their different colours which aids in flushing..