N55 Brake Fluid Flush

Brake fluid absorbs water, and BMW counts its life in years, not miles. On an N55 the job is 1.0 L of low viscosity DOT 4, a pressure bleeder and a flush at each wheel. Get the label on the bottle right and the rest is a patient flush.

Covers these US N55 cars: 135i, 335i, 335i GT, 435i, M235i, M2, 535i, 535i GT, 640i, 740i and 740Li, X3 35i, X4 35i, X5 35i and X6 35i. Not the ActiveHybrids.

How often

E70, E71, E82, E88, E90, E92, E93BMW's US rule: every 2 years.

Any other N55 built July 2013 or laterFirst change at 3 years, then every 2 years.

F-series built before July 2013Every 2 years is our reading of BMW's table. It isn't a line BMW prints for those cars.

Owner and forum advice, not BMWEvery 2 years on any N55. A safe default if you don't know the build date.

If your car has a brake fluid item in its service reminder, reset it after the job: steps below.

The fluid

DOT 4 LVLow viscosity DOT 4. BMW's own bottle has a black cap. Read the label: look for DOT 4 LV or ISO 4925 Class 6 (ATE's data sheet for its low viscosity fluid uses the Class 6 name).

BMW's rule: a car with DSC and no pre-charge pump must have the low viscosity fluid. Every other car may have it too, and it mixes with regular DOT 4.
Which yours is: BMW's data doesn't tell us which N55 cars have the pump. LV is allowed on all of them, so fill LV and you're right either way. Some forums say any DOT 4 will do. We don't gamble on a brake system.
Silicone-based fluid: not approved. BMW says it is more compressible.

ATE DOT 4 SL.6Our listing says it's for BMW DOT 4 LV, and the bottle may print ISO 4925 Class 6 instead. It's a 5 L jug and the job takes 1.0 L.DOT 4 LV, 5 L $95.99 →

BMW's own LV fluidBMW 83 13 5 A82 511The 1.0 L bottle, one job's worth.

1.0 LFlushing included, on every N55 car. BMW's parts catalog gives the same number for all of them.

IA EURO illustration of the brake fluid reservoir with the cap lifted off, the sealing ring circled and the MAX and MIN marks — Figure 1The reservoir with the cap lifted off. The cap's sealing ring and the MAX and MIN marks are circled or labelled. Generic layout: yours may differ.

Figure 1The reservoir with the cap lifted off. The cap's sealing ring and the MAX and MIN marks are circled or labelled. Generic layout: yours may differ.

What you need

Pressure bleederWith an adapter for the reservoir, set to 2 bar at the most. That is BMW's routine method, so it's the only one this page teaches.

Hose, bottles, wrenchA hose from each bleed valve into a catch bottle, and a bleeder wrench. One vendor's E90 listing says the rear valves need a 9 mm wrench: check yours.

Water and ragsFor spills, right away.

Brake fluid eats paint. BMW says wash any splash off with water at once. Don't keep it in a drink bottle. Old fluid is hazardous waste.

Never let the reservoir run dry. Shop rule, not BMW's: watch the level the whole flush. BMW says never pour old fluid back into the bleeder.

Car up? Stands, a lift or ramps, never a jack alone. We have no BMW source for lifting points, so check your owner's manual.

Bleed in this order

Rear rightRear axle first. Flush until clear, bubble-free fluid comes out.
Rear leftSame.
Front rightSame.
Front leftSame. Last corner.
ReservoirLevel to MAX, cap on, check the seal in the cap.

Torque

Bleed valveDepends on the caliper. Send us your VIN and we'll send yours.

Set up

Cover off. Take off whichever cover is in the way of the reservoir. BMW's steps name the cowl cover, the engine compartment cover and the left microfilter housing cover.
Figure 2The cowl panel at the base of the windshield, held by clips along its edge. Generic layout: yours may differ.
Figure 2Close
Water drain under the brake booster. BMW's older service hint says to check it and clean it with the fluid change.
New fluid in. Fill the reservoir with new fluid. Bleed the air out of the bleeder's hose before you connect it.
Figure 3The reservoir with the cap lifted off. The cap's sealing ring and the MAX and MIN marks are circled or labelled. Generic layout: yours may differ.
Figure 3Close
Connect the bleeder, 2 bar at the most.
Figure 4The pressure bleeder adapter on the reservoir. Generic layout: yours may differ.
Figure 4Close

Flush

Rear right valve first. Hose on the valve, the other end in a catch bottle. Open it, flush until clear, bubble-free fluid comes out, close it.
Then rear left, front right, front left, the same way. Watch the reservoir.
Bleeder off, then away. Switch it off first, then take it off. Set the level to MAX and close the reservoir. Mind the seal in the cap.
Wash off spills with water. If the wheels came off, refit them to the torque in your owner's manual before the car comes down.
Manual gearbox? BMW also has you change the clutch fluid, by bleeding at the slave cylinder.

Pedal firm before the car moves. Shop rule, not BMW's: press it. It has to feel firm. Soft or sinking: don't drive, there is still air in a line.

The DSC bleed routine is for repairs

BMW has a second bleed that runs from its diagnosis software. It is for repairs that open the hydraulics: the master cylinder, the hydraulic unit, or the lines and parts between them. A routine fluid change doesn't call for it. The pressure flush from the reservoir is the routine method. On cars with an electric parking brake, BMW has an extra rear caliper bleed too, only for when a normal flush can't clear the air. The caliper comes off. That's the exception, and not a DIY-friendly one.

Reset the brake fluid reminder

Last, after the work. BMW's in-car steps for the speedometer display. They aren't tied to a model, and F-series clusters differ:

Ignition on, engine off. On a push-button F-series car, owners say that means Start/Stop without your foot on the brake.
Hold the trip reset button about 10 seconds, until the first service item shows.
Step to the brake fluid item with a short press of the button on the turn signal stalk.
Hold the button about 3 seconds until Reset? shows, then about 3 seconds again to confirm.

The 80 percent rule. In the car, BMW only lets you reset an item under 80 percent available, with no Check Control message and the date right. Above that you get a reset lock, and only a shop's BMW diagnosis tool clears it. Our reading, not BMW's: change the fluid very early and you can hit this.

Owners (not BMW) say F-series cars work the same way, but the buttons sit in different places. If yours doesn't match, send us your VIN and we'll send yours.

Where people mess it up

Wrong bottle. Read DOT 4 LV or ISO 4925 Class 6 on the label. Silicone-based fluid is out.
Too much pressure. BMW caps the bleeder at 2 bar.
Dry reservoir. Keep it topped up all the way through.
Old fluid back in the bleeder. BMW says never.
Paint. A splash left on the fender or cowl: water, at once.
Driving before the pedal check. Firm pedal first.
Running the DSC routine for nothing. It is a repair procedure.

More basics: cabin filter and engine air filter.

Steps, the interval and fluid rules come from BMW's repair instructions for replacing brake fluid, its service bulletin on brake fluid and its service reset instructions. The 1.0 L quantity comes from BMW's parts catalog up to 2020. Owner and vendor experience is labeled where we use it. Check yours by VIN.