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      06-27-2020, 03:48 AM   #1
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c0bra's Avatar

Drives: N54 1er Cabrio
Join Date: Aug 2018
Location: NY

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DIY: Power Steering Fluid Flush and Reservoir / Filter Change on N54

I posted this DIY on 1addicts and realized it is directly applicable to E9x. Car is 135i N54 without active steering.

This method utilizes the power steering return line to completely flush the fluid. No need to remove underbody cover, no mixing new fluid with old, and no fooling with crush washers or banjo bolts. This service can be done solo. Use this information at your own risk!

Even though there is already info out there, I thought I'd post a more comprehensive DIY. I referenced the ZF flush and bleed method, as well as these 2 threads: DIY: Power Steering COMPLETE Flush and DIY: 128i Power steering fluid filter change/fluid flush (Non-active steering models).

Parts / Tools

Power Steering Reservoir Kit - 512051KT from FCP includes:
ZF reservoir with integrated filter, new cap and o-ring
2 OEM Clic-R hose clamps
Pentosin CHF 11S - 1 liter (get a 2nd liter if you want 100% fluid flush)

10mm socket
Turkey baster, syringe, or similar
T20 torx driver (optional, less mess)
Clic-R clamp pliers (optional, highly recommended for OEM clamps)
Flat head screwdriver and/or hose removal pliers
5-6 feet of 1/2" OD clear tube and catch pan or bottle
2 small hose clamps - I used micro size 6 worm gear style
Jack stands (optional, highly recommended)
Towels and rags

Kit and some supplies


1. Put the front of the car up on jack stands, just enough to get the tires off the ground. This makes it easy to turn the steering wheel later. Stuff a bunch of towels under and around reservoir and hoses to catch spilled fluid. I also lay some towels over the fender and headlight area to keep things clean.

2. Remove 2 10mm bolts securing the reservoir bracket to the chassis. Empty out as much old fluid as possible using turkey baster or syringe. Optional - Remove T20 screw securing filter in the reservoir. I used a magnetic tool to take out the screw. Careful not to drop it! Pushing filter aside and tilting the reservoir, I pulled around 4 more ounces out with the turkey baster.

10mm bolts and reservoir

Filter and T20 screw on new reservoir

3. Using Clic-R clamp pliers, remove the 2 hose clamps. Pliers must be positioned the correct way to unlatch the clip with a good squeeze. Alternatively, pry the clip open with a flat head screwdriver.

Clamp removal position

4. Remove the reservoir by prying off the hoses. The return hose (bottom, smaller) is likely melted on and requires some effort. I got it off by working a small flat head screwdriver between the hose and the reservoir. With the reservoir off, remove the bracket using 10mm socket and replace on new reservoir.

5. Plug the return line inlet (bottom, smaller tube on new reservoir) with a vacuum port plug or using the plastic cover that it comes with. Secure with small worm clamp which doesn't need to be too tight since it will not be pressurized.

Reservoir return inlet plugged

6. Connect new reservoir to the feed hose (top, larger). A lot of people use regular worm type clamps, but I opted to use the OEM style after reading up on the differences. Clic-R pliers must be positioned the opposite way to work. You will hear the clamp click on when engaged properly. Careful not to let the clamp slide down the hose! You will have to fish it out from the depths of the engine bay, ask me how I know.

Clamp install position

7. Stick clear tube into the return hose and secure with another worm clamp. 5+ feet of hose will get you over the headlight and bumper to a catch can on the floor. Completely fill up the new reservoir with fresh fluid.

8. Put the key in the ignition but do not start the car. Turn the wheel left and right, almost full lock to lock, at a moderately quick pace. Dirty old fluid will be pushed out through the clear tube into the catch can. You can monitor the flow by peeking at the tube through the crack of the open hood or by standing outside the car while turning the wheel. After several turns, check the reservoir level and refill when low.

Dirty brown fluid turning green

9. Continue turning the wheel and refilling as necessary until you start to see green fluid in the tube. With 1 liter, you can only flush 2-3 full reservoirs worth of fluid since you need to keep some for the final fill. Careful not to run out of fluid! 2L will ensure full 100% fluid flush, where 1L probably gets 80-90% done. Try to time the last fill so that your reservoir is mostly empty when finished. Use the turkey baster or syringe to empty as best you can.

10. Remove the clear tubing and clamp from the return hose. Loosen clamp holding the plastic cover on reservoir return inlet. When you pull off the cover, use your finger to quickly plug the hole to minimize fluid spill. Connect the smaller hose onto the inlet the same way you connected the larger feed hose (see step 6).

All hooked up

11. Fill the reservoir, checking the cap dipstick for proper level. Start the car and verify no leaks. Turn the wheel left to right several times to bleed any air in the system. Turn the car off and drop it down off the jack stands. Check the fluid level one last time and go for a ride!

Check fluid level

Here's some of the old dirty fluid! This is at 30k miles, but fluid is 11 years old. There's some stuff floating around in there. Yuck! I plan to change this every 25k or 4 yrs from now on.