Procedure for Flushing Power Steering System (Tech Article)

[Rich911E]

Flushing the Power Steering Fluid

Well, looking at my disgustingly colored power steering (“PS”) fluid and hearing a little noise at idle from what I think was the PS pump, I decided the flush the power steering system. There is a small filter in the bottom of the PS reservoir and this can get clogged over time. My car has 209K miles and I don’t think it has ever been changed. After extensive searching on the Net for someone else who had done this and found none, I decided to try a simple procedure that seems to work. I thought I would share it with the members of this board.

Time: About 1.0 to 1.5 hours (including clean up)

You will need:

a. new power steering reservoir (about $30, save the little plastic plugs that come with it)
b. an oil drain pan
c. a turkey baster (raid the kitchen utensil drawer)
d. screwdriver/nut driver for clamps
e. 10mm box/open end wrench
f. 1 gallon of ATF

Procedure:

The power steering reservoir is located on the driver’s side of the engine compartment mounted to the left front shock tower. If you can’t find it you had better give up now.

1. First, be sure to suck out as much of the PS fluid as you can from the reservoir with the turkey baster. This will make the job much cleaner.

2. Remove the steel bracket that holds the PS reservoir. Spread the round part around the PS reservoir to remove upwards.

3. Loosen the screw clamps that hold the lines to the bottom of the reservoir and very carefully remove the lines from the reservoir with gentle persuasion. You don’t want to crack or break these. Mine came off OK and they have been on there for 14 years so it shouldn’t be much of a problem.

4. There are two hoses that go to the power steering reservoir, one slightly larger than the other. The larger diameter hose is the feed and the smaller is the return line from the pump. Put the drain pan under the car and route the smaller diameter hose (return line from the PS pump) down so that it pumps the old fluid into the drain pan.

5. Your new PS reservoir should have come with some little plastic caps to cover protect the hose ends. Remove the plastic cap on the larger diameter opening (pump feed) and leave the plastic cap on the smaller diameter (return line) opening. If you didn’t get little plastic caps, seal off the smaller diameter opening with a large vacuum cap or rubber stopper or something. There is no pressure behind it so you just want to keep it from leaking.

6. Connect up the larger diameter (pump feed) hose to the PS reservoir and tighten the screw clamp. Just wedge the reservoir in place for the moment because getting at the clamps and hoses with the mounting bracket in place is a pain.

7. Fill up the reservoir with ATF. Start the car and the fluid will very quickly (3-4 seconds) drain from the reservoir. The best would be to have a buddy stand there and pour in the ATF quickly while the car is running to avoid having to turn the car on and off. I had to do it by myself and I had to turn the car on and off refilling the reservoir 4-5 times to flush. Perhaps others can suggest some system to facilitate this procedure (like a large funnel to keep feeding the reservoir). Use about three-fourths of the gallon of ATF, saving enough to fill the system when you are done.

8. With the engine off, route the smaller diameter hose up to the bottom of the new PS reservoir and quickly remove the plastic cap and swap on the reservoir and swap on the hose, and tighten the claim. Wipe up the small amount of ATF that spilled.

9. Reinstall the PS reservoir bracket and fill the PS reservoir with ATF.

10. Start the car and then check the level of the PS reservoir again.

This worked for me and stopped the noise I was getting. Suggestions and improvements are welcome.

Rich

[Simon S]

Thank you for taking the time to write that up Rich.

My PS fluid resembles gravy..

[furlong]

Rich911, Thanks very much for writing this up! My '86 325es just started graunching noises when turning the wheel at startup. I had a friend look at it last Saturday and we decided to replace the reservoir, so I parked the car and ordered one from Pelican. Neither of us has done this before and I for one was surprised at the amount of ATF needed. Will advise you how it went, but I don't expect any problems as your article is very clear.
jimfurlong2002@yahoo.com

[furlong]

Rich911, Finally ready to go on replacement and I noticed the hose clamps underneath are NOT reusable. Want to buy some clamps before starting. Any idea what 24.5R means? I can see that on the bigger stock clamp. Measures just under 1" diameter, so I will presume that is a metric diameter in millimeters. Return line is about 5/8" ~16mm. JCF

[Rich911E]

I don't think there is anything special about the clamps -- probably just the metric size or something.

Rich