[cfm56d7b]

Appreciate everyone's input and specially after warranty expires.

[Billfitz]

Brake fluid gets contaminated with water over time, which causes all sorts of problems. BMW errs of the side of caution, recommending a rather short 2 year interval. Some manufacturers don't mention it at all, most say 3 or 4 years. None are really exact because AFAIK none have a fluid moisture content measuring system. I bought one of these, so that I'd know and not change it either before or after it needs it.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I check the fluid twice a year, so far it's still at 0% water content.

You should get fluid replacement anyway with your maintenance agreement. You can find when it's due on your iDrive.

[cfm56d7b]

Thanks for sharing. Similar thread in X5 forums also suggests a brake flush every 2 years. My 2017 BMW 44i GC is 2 years old. Time to plan it.

[Billfitz]

Maybe you misunderstood my post. My '15 still has zero water content in the brake fluid, so I haven't changed it. When I do see it hit 1%, which is still 1% below acceptable, I will. The two year recommendation is because unless you have a tester you can't know if it's still good or not, so BMWs stance is better safe than sorry, especially as the average owner wouldn't have a tester, and probably couldn't even find the master cylinder if they did.

[bavarianride]

Originally Posted by Billfitz

I bought one of these, so that I'd know and not change it either before or after it needs it.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I check the fluid twice a year, so far it's still at 0% water content.

This looks like a handy tool, plus some coolant strips. Now if there are test tools for AT fluid, and/or engine oil, that will be great!

[cpxchewy]

Originally Posted by Billfitz

Maybe you misunderstood my post. My '15 still has zero water content in the brake fluid, so I haven't changed it. When I do see it hit 1%, which is still 1% below acceptable, I will. The two year recommendation is because unless you have a tester you can't know if it's still good or not, so BMWs stance is better safe than sorry, especially as the average owner wouldn't have a tester, and probably couldn't even find the master cylinder if they did.

It's actually better to bleed a little bit of brake fluid from each corner and then test those. If you just gravity bleed it a tiny bit it actually helps remove any bubbles that might come up as well + give you an insight of any contaminants near the caliper as opposed to "clean" brake fluid at the master cylinder.

[enjoythemusic]

2 to 3 years. Use turkey baster to get as much fluid out of under hood reservoir. Then add fresh brake fluid there.

Go to the FURTHEST brake caliper (usually rear right / left) and start sucking out / pumping the new fluid through.

Be sure to keep under hood reservoir loaded with fresh fluid.

Then suck out / pump fluid through the front calipers.

Check under hood level to stock.

Done.

Have used SpeedBleeders with good results if you plan to do this alone. Of course there are other types of apparatus to help with bleeding of brake fluid. The point is to get ALL the old fluid out while ensuring no air bubbles are within your brake lines / calipers.

https://amzn.to/2S9hzxV

[MacklinUSOB]

Interval depends heavily on how hard you are on your brakes and if you have moved from OE fluid or not.

On the stock fluid without much agressive use I would say go 2-3 years between flushes. If a full flush isn't needed, bleed and replace 1 quart of it instead.

As for me, I use my brakes agressively often and have several track days throughout the year. I bleed after every other track day and flush at the beginning of every season. If you track often, some organizations require you to have flushed within the last 6 months or so, but not all. I also use RBF600 which has a higher boil point, but is also more hygroscopic which further necessitates my increased bleed/flush interval.

With the frequency I do it I spent 60 bucks on a power bleeder and catch bottles (like the one enjoythemusic mentioned, I have the Motive). It makes the process extremely easy, start to finish is about 30 minutes and you are saving money from the first time you use it.