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DIY Video – Changing Power Steering Filter and Fluid – BMW and MINI

December 29, 2010

The power steering fluid and filter are one of the most overlooked preventive maintenance areas on most BMWs and MINIs. (Think about it – when did you ever changed the power steering fluid on any vehicle?) On BMWs, this system provides boost not just for the steering but often for the power brakes and self-leveling suspensions, as well. Time and time again, we’ll look at the power steering fluid in a BMW or MINI and it is filthy! (Running on old, degraded fluid will shorten the useful life of the steering rack/gearbox, brake booster, fluid pump, etc.) The fluid should be bright, clear red or, depending on the application, just clean and clear.
One of the reasons this system gets overlooked is that there is no direct provision for changing the fluid; therefore the job is a bit more tedious. But it is not so tedious that it should be ignored. We recommend a biennial (every other year) or 50,000-mile fluid change for the power boost system. Additionally, most systems have a fluid filter incorporated into the fluid reservoir. (A lot of mechanics do not even know that this filter exists!) Change the filter when changing the fluid. (This is also a great time to replace any leaking power steering hoses.) There are three different fluids used in BMWs and MINIs; the correct fluid is typically noted on a label on the reservoir cap. We can assist in determining the proper filter and fluid for your BMW or MINI.


There are options in what method you use to flush the power steering fluid. They range from easiest and least messy (while using a bit more fluid) to getting under the car, disconnecting hoses and catching and draining the fluid.


1) Under the hood method: Remove the fluid in the reservoir using a fluid transfer pump (part #FP 500). Replace the filter or reservoir/filter (whichever is applicable, depending on the model). Note that there may still be a fair amount of fluid in the bottom of the reservoir. (Be prepared to catch the fluid with a Pig Mat.) Replace the filter or reservoir with integral filter (plastic reservoirs). Refill with the appropriate fresh fluid. Start the engine. Keep sucking out old fluid and refilling with fresh, letting the engine run for a few minutes in between each removal/refill. Eventually, the fluid being extracted will be bright and clear indicating that most or all of the old fluid has been removed.


2) Hose drain method: You can disconnect all of the hose connections at the pump, steering rack and reservoir (after first sucking most of the old fluid from the reservoir) and let everything drain. Install the new filter/reservoir. Reassemble all of the hoses and then follow method 1, above, for refilling.

3) Full flush method: Suck the fluid from the reservoir. Install the new filter/reservoir. Remove the return fluid hose from the bottom of the reservoir. Place the hose in a bucket (you may have to attach a double-ended nipple and more hose to get to the bucket). Use a plugged piece of hose to cap the nipple on the reservoir (where the return hose was attached). Be prepared with a few quarts of fresh fluid. Fill the reservoir. Have a helper start the engine and then keep pouring fresh fluid into the reservoir until the fluid coming out of the return hose (in the bucket) is fresh and clear (do not let the reservoir go dry). Turn off the engine. Re-attach the hoses. Fill the reservoir and start the engine; adjust the fluid level as needed.



Follow along as we replace the reservoir/filter and flush the fluid (using method-1) on a 2001 330xi, and see the DIY video at the top of this post.

1. Remove air filter box as follows: using the hose clamp driver, loosen hose clamp on intake boot to Mass Air Flow sensor (MAF); unclip harness plug from MAF; remove two Torx or hex head bolts securing the air filter box to the inner fender; separate the intake boot from the MAF and lift the rear of the filter box out of the bay, while  separating the cold-air snorkel from the passenger side of the box; lift the box up and out (fig. 1).

2. Use the fluid pump to transfer as much fluid as possible from the reservoir to a drain pan (fig. 2). The filter is in the bottom of the reservoir, so you will still have a few ounces of fluid that cannot be removed with the pump.

3. Remove the two 13mm bolts that secure the reservoir mounting bracket to the oil filter housing assembly and pull the reservoir toward the driver side of the engine bay (fig. 3).

4. Place a sheet of the Pig Mat oil absorbent mat under the reservoir, with the drain pan on the mat. Cut off the original hose crimp-clamps, using end-cutters. Hold the reservoir over the drain pan and pull the hoses from the reservoir nipples. Drain the reservoir and the hoses (fig. 4).

5. Clean up the hoses with the Scrubs In A Bucket wipes (fig. 5).

6. Loosen the clamping bolt on the reservoir mounting bracket. Remove the bracket from the old reservoir and install it on the new one. Do not fully tighten the clamping bolt.

7. Install the hoses to the new reservoir, using new hose clamps (fig. 6).

8. Install the reservoir and mounting bracket to the oil filter housing. Tighten the mounting bracket clamping bolt.

9. Install the air filter box.

10. Fill the reservoir with fresh Dexron-III or Pentosin fluid as appropriate.

11. Start the engine. Let it run for a couple minutes then use the fluid transfer pump to remove the fluid (with the engine running).  Remember, there is still fluid under the filter top plate so you are not running the system dry (fig. 7). Add fresh fluid, run for a couple of minutes and repeat the fluid removal and refilling. Do this until the fluid is clear and does not cloud up. Recheck the fluid after a couple of days. If fluid is no longer bright and clear, perform a couple more fluid exchanges.

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