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Old 06-28-2010, 08:50 PM
pigeon pigeon is offline
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Location: Farmington, NY
Join Date: Nov 2005
Posts: 229
Mein Auto: 06 750Li
Originally Posted by USALEXUSBMW750 View Post
Just reset your idrive maintenance section.
Then cry when the brakes fail because the old fluid boiled, or expensive parts corroded or failed because of the old fluid.

Changing the brake fluid is easy. What you need:
- 1 sealed 1 liter container of new brake fluid, DOT4 - I like ATE Super Gold 200 and Super Blue because you can tell from the color change when the fluid is completely flushed out. I've also used Valvoline Synthetic with good results.
- 1 turkey baster from the dollar store
- 14mm (IIRC) box end wrench
- A length of clear vinyl tubing to fit over the brake bleeder
- A clear container to catch the old fluid (old soda bottle)
- In lieu of the last 2, a one man brake bleeder kit from Sears - it has the tubing and a catch cup all in one.
- Jack, stands, wheel chock

Start at the wheel farthest from the master cylinder - passenger rear - chock the diagonal corner wheel, loosen lugs, jack car, place stands, remove wheel.
Pop the hood, go to the master cylinder, wipe clean around the cap, then remove it. Use the turkey baster to suck as much of the old fluid out as possible - no sense in pushing it all through the system. Refill the reservoir with new fluid.
IMPORTANT - keep a close eye on the master cylinder reservoir and do not let it run dry or you will be bleeding air out of the system forever.
Place the box end wrench on the bleeder, then the vinyl tubing. Place other end of vinyl tubing into the clear container and submerge in a bit of new fluid, or the old fluid you sucked out of the master. This will prevent air from being sucked back into the bleeder.
Open bleeder (lefty loosey) about 1/2 turn.
Pump brake pedal slowly and repeatedly to flush fluid through the system until new fluid comes out of the bleeder. Do not push all the way to the floor but make shortish 1/2-3/4 strokes - you don't want to run the seals in the master beyond the area they've been running in or you risk tearing them. Take your time so you don't introduce air into the system.
REPEAT - IMPORTANT - keep a close eye on the master cylinder reservoir and do not let it run dry. Trust me, that sucks.
Once you have new fluid at the bleeder let it continue to gravity drip for a little bit to be sure you have no bubbles in the system (that's why you use clear tubing) then close the bleeder.
Replace wheel, repeat with driver's rear wheel, passenger front and driver's front in that order.
Now you can reset the warning in the "secret menu".

Caution - brake fluid will remove paint almost immediately, so don't spill it and keep some way to flush it off the paintwork (not just try to wipe it off) handy, like a hose or a bucket. it's also hazardous waste, so dispose of properly.

It's not hard, just time consuming. Brake fluid sucks up water from the atmosphere, which lowers the boiling point and can cause the brake system parts to rust internally. Change it every 2 years at least.
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