BMW recommends flushing brake fluid every two years for everyday street driving.
Tools:
- Flathead screwdriver
- 9 mm wrench
- Box end wrench may be helpful
- Motive European Power Brake Bleeder w/ Adapter
- Genesis Cable Bleeder Bottle
- Turkey baster or syringe to suck out old brake fluid
- 17 mm socket and ratchet to remove wheels
- Torque wrench for wheel lugs
- Jack and jack stands
- Brake fluid:
- 2 x ATE Original SL.6 DOT 4
. Lower viscosity, better for street use.
- 2 x ATE Original TYP 200 DOT 4
. Lower viscosity, better for street use. 
- Shop rags or towels to place around brake reservoir and underneath brake caliper for spills.
- Break torque on wheel lugs using 17 mm socket and ratchet
- Safely jack up E39 and place on jack stands.
- I use Jack pad adapters to prevent crushing the plastic jack points.
- Remove lug nuts and wheels.
- Pop open hood and locate driver side cabin air filter tray.
- Use a flat head screw driver and push down on the plastic tabs to disconnect air duct. (Red)
- Unclip metal latch holding air filter cover. (Purple)
- Remove air filter tray cover. (Yellow)
- Remove cabin micro filter.
- Remove rubber trim around cabin filter tray.
- Disconnect electrical plug from hood sensor. (Green)
- Squeeze and remove metal clip from screw holding tray to body of vehicle. (Blue)
- Lift and remove cabin air tray.
- Now you have access to the brake fluid reservoir.
- Open reservoir cap (red circle) and suck out old brake fluid with a turkey baster.
- Place rags or towels around reservoir to soak up spills. Brake fluid will damage and remove paint.
- Fill brake reservoir to max with new DOT 4 brake fluid.
- Dump remaining brake fluid into Motive brake bleeder.
- Install adapter to brake fluid reservoir.
- Pump brake bleeder to 15 psi.
- Go to right rear brake caliper and locate the brake bleeder nipple.
- Now is a good time to inspect brake lines for any wear, rot, or damage.
- Remove cover from bleed screw and attach hose from bleeder bottle.
- If using 9 mm box end wrench, place it on bleed screw before attaching hose from bleeder bottle.
- I sprayed penetrating oil on the screws for ease of loosening.
- Loosen bleed screw and wait until all the air bubbles and dirty brake fluid has left the hose.
- Look for new, clear brake fluid before tightening bleed screw.
- Remove hose and reinstall cover.
- Pump Motive power bleeder to 15 psi.
- Repeat the process for the left rear caliper, right front caliper and finally the left front caliper.
- Make sure power bleeder is at 15 psi before each bleed.
- When completed, remove pressure from the power bleeder side and fill reservoir to max.
- Reinstall reservoir cap.
- Reinstall cabin micro filter tray and rubber trim piece.
- Reinstall and torque wheels.
- Jack and remove jack stands to lower E39.
- Test the brakes by moving a few feet before going on a drive.
Buy two 1-Liter bottles of brake fluid. One should be enough, but you want to have an extra liter in case of spills or shortage of fluid.
Gently loosen and tighten the brake bleed screws, it is easy to strip and damage them.
It is normal to have air bubbles in the hose from the power bleeder to the reservoir during fluid flush process.
Cover all areas where brake fluid may spill. Brake fluid will strip paint.
Minimize the amount of time new brake fluid will be exposed to air. Brake fluid is hygroscopic so remove the reservoir cap only when necessary. Properly dispose of any opened brake fluid bottles if not using in the near future.
This tutorial may apply to other BMW models.
I don't think the previous owner ever changed the brake fluid or within the past five years. The old brake fluid was extremely nasty and almost black.
