Changing Brake Fluid

[belrix]

OK I'll admit I didn't change my NCX brake fluid at 12,000 miles.

Bad owner, bad!

Now I'm going to change it but have a question.


When pumping out the old fluid do I keep pumping until the master cylinder is dry or keep adding fluid until the fluid being flushed is clear?


Thanks a million!



Sent from my iPad using Tapatalk

 

[HarveyM]

I've always added fluid until it runs clear.
Once you have air in the system, your brakes are .... 'pucked'.

 

[belrix]

Thanks! That is what I was thinking, make sense.

Thought I would check since I am not a mechanic.

 

[670cc]

Never let the master cylinder go empty. Air in the system is bad, bad, bad. Air compresses easily; brake fluid does not.

Obviously, if air is in the system, it can be bled out. How else would you fill a new brake hose or new caliper? But save yourself the extra time and hassle of trying to extract all air bubbles and just don't let any air in.

Also, put a towel over your bike's body work and around the master cylinders during the process. Clean everything up well after reinstalling the master cylinder cover. Brake fluid eventually dissolves or damages paint.

One thing I've never figured out. The labeling on the master cylinder cover always says to add fluid only from a sealed container. But, I can't ever seem to get the fluid out of the bottle when it's sealed. (Bad joke .)

 

[dduelin]

Yes, we never want to pump the reservoir dry and introduce air into the system. When replacing the fluid I remove the old fluid in the reservoir first then top off the reservoir so the old fluid is only that in the lines and in the caliper, with new fluid coming down to flush out the lines. When I did mine I created this thread:

http://nc700-forum.com/forum/garage...-fluid-replacement.html?highlight=brake+fluid

 

[belrix]

Wow! Awesome write-up, Thank You!


Sent from my iPad using Tapatalk

 

[happy]

Although I admit I am not mechanically inclined (compared to say Beemerphile, Dave and some of the expert mechanics here), i did do some work on my bikes in the past.

Changing brake fluids is one thing I could do.
On top of the advice already given here, I would say to add fluid whilst you are pumping out the old fluid.
Best to get a buddy to help out although it can be done alone.
One pumps the handle and tops up fluid whilst the other works on the valve nuts.

Else buy a bleeding kit which has a single direction valve bleeding hose. That helps a whole lot.

I recommend changing fluid once a year if possible. (Although I don't do it myself)

Sent from my LG-D955 using Tapatalk

 

[DirtFlier]

[..I remove the old fluid in the reservoir first then top off the reservoir so the old fluid is only that in the lines and in the caliper, with new fluid coming down to flush out the lines...]

+1 on that. No reason to pump old fluid through the system plus I use the opportunity (empty reservoir) to wipe clean any crud in the bottom of the reservoir before refilling. It also makes it much easier to see when you're getting fresh fluid out of the bleeder line because there is a clear line of where the old fluid ends and new fluid begins.

 

[happy]

[..I remove the old fluid in the reservoir first then top off the reservoir so the old fluid is only that in the lines and in the caliper, with new fluid coming down to flush out the lines...]

+1 on that. No reason to pump old fluid through the system plus I use the opportunity (empty reservoir) to wipe clean any crud in the bottom of the reservoir before refilling. It also makes it much easier to see when you're getting fresh fluid out of the bleeder line because there is a clear line of where the old fluid ends and new fluid begins.

That is the right thing to do. But since I only use the bottle once (after opening the new bottle) , I would say it is ok to pump out the old fluid through the hoses any way. I dont use fluid which has been sitting around in a bottle which was already opened a while ago. It is quite a cheap thing IMHO.

One can use a big syringe to suck out the old fluid but I dont bother.

But it is good tip if you really wanna save money.


Sent from my LG-D955 using Tapatalk

 

[bvogel7475]

You should always use a new sealed bottle of brake fluid because once a bottle is opened it immediately starts drawing water into the fluid. It's a air/chemical reaction that degrades the ability of the fluid to absorb heat. However, you want your break fluid to absorb water. That's one way it helps keep your brake system clean and free of water/ice. You only want it absorbing water in your system though, not the water in the air. Transferring pressure through the brake lines and caliber to the brake pads generates a lot of heat and brake fluid boils at over 400 degrees F when it is new. That boiling point decreases over time as it absorbs water. Your brakes are the most important safety feature of your bike and trying to save money on fluid by using older opened containers could generate disastrous results.

If you really want to get technical with how brake fluid works. Read this. It may put you to sleep though.

http://www.centricparts.com/files/technical guides/brake-fluid.pdf

 

[b_rubenstein]

My suggestion is to empty the reservoir of old fluid and refill with fresh. To remove the old fluid from the lines, I use a small hand vacuum pump (Mityvac or equivalent. Harbor Freight sells a decent one for around $15). The pump will draw out the old fluid and any air in the system. This will still leave to old fluid in the caliper and any moisture in the fluid can still corrode the piston. I get rid of this fluid when changing brake pads by putting a tube over the bleeder, crack open the bleeder and push the piston back into the caliper. This will force the old fluid out of the caliper. For any vehicle with ABS, forcing the old, contaminated fluid out of the caliper and will keep from forcing it through the ABS valves. Usually purging all the fluid every other year is sufficient.

 

[Gbjbany]

If you want to go crazy you can also use speed bleeders https://bikeeffects.com/proddetail.asp?prod=SB8125L - they make changing the fluid a breeze