Howto: Power steering flush
 

I changed my power steering fluid over the weekend and wanted to document the process for any hands-on folks here. Because I wasn't sure what fluid was in there and it smelled pretty burned, I wanted to get every bit out as well as any contaminants. This method for flushing is basically the same as the Rodney flush (or Gibbons method for the folks in the Volvo world) used on transmissions so I can't take credit for coming up with it. Basically what you'll be doing is disconnecting the hose that feeds fluid back into the reservoir and routing it into a jug. Then fill the reservoir, spin the wheel, refill, and repeat until fresh fluid comes out. This whole thing took less than an hour and is pretty low risk. For materials you'll need a new hose clamp and 3 liters of power steering fluid. For my car I needed something that met the (IIRC) 345.0 spec. A lot of people recommend Pentosin CHF 11S which is an excellent choice. I ended up going with Ravenol SSF since it not only listed the spec needed, but was a replacement for CHF 11S to boot. My impression is that it was a higher quality fluid overall and given that it was a few dollars cheaper than 11S on Amazon, it was a no-brainer. You'll also need 3-4 feet of 3/8" PVC hose, a jack, funnel, small flathead screwdriver, a few clamps, container for the old fluid, and fluid pump, though the pump isn't strictly necessary.

Start by removing the air filter housing and the ducting running over the power steering reservoir. Remove the cap and pump out what you can. I only got 2-3 good pumps before it went empty, which makes this step optional.

https://cimg6.ibsrv.net/gimg/www.mbw...d174d6ce5d.jpg

Next, disconnect the return hose from the radiator. It's the one right below the large coolant connection on the right. It's held in place with an Oetiker clamp, so grab that small flathead screwdriver.

https://cimg1.ibsrv.net/gimg/www.mbw...b6597171d9.jpg

Put a rag/towel underneath since you'll get some spillage and disconnect the hose. Throw a thumb over the end of the hose and radiator connection, though you shouldn't get much coming out. Move the hose up and out of the way. I used a clamp to hold it next to the ABS module while I worked. Push the 3/8" tubing onto the radiator connection and route the other end into your fluids collection container. If your tubing was really stiff like mine it may be necessary to clamp it onto the container.

https://cimg4.ibsrv.net/gimg/www.mbw...9e7293d480.jpg

Lift the front of the car with your jack. Don't forget to chock the rear wheels. There's a jacking pad in the front of the car in the center. Raise it enough to get the wheels 2" or so off the ground.

Now for the fun part! Do not turn the engine on at any point until you're completely finished. Slowly fill the reservoir to the top with the new fluid. Turn the steering wheel to full lock in one direction. Refill the reservoir. Turn the wheel in the other direction again to full lock. Refill the reservoir. Continue turning the steering wheel from and to full lock and refilling the reservoir. You don't want it to run dry because then you'll introduce air into the rack and will need to deal with purging it. Don't spin the steering wheel too quickly. It took me about 45 seconds to turn from one full lock to the other. Keep an eye on the color of the fluid draining out. At some point around the end of the second liter of fluid it should be looking pretty clean. Continue until you've gone through the 3 liters, but stop when you get to the last 1/4 of the last bottle. You'll want a little left to make sure the level is good.

Disconnect the PVC hose and reconnect the return hose. This is where you'll need a new hose clamp. Using the cold marking on the dipstick on the cap, refill the reservoir (careful, you won't need much) and turn the wheels back to straight ahead. Lower the car, reassemble the air ducting and go for a quick drive around the block, completely turning the wheels in each direction at least once. Shut off the engine and check the level again.

Hope this helps!

Very nice write-up, Thanks! How were you able to disconnect Oetiker clamp with a screw driver!

Perfectly on time. Gonna be doing this pretty soon. Thanks

Thanks!

To remove an Oetiker clamp with a screwdriver, you work the screwdriver into the little loop/ear that sticks up and basically just twist it until the catches on the band pop free. You can also remove it with cutters. Because of the way this clamp is situated, you'll probably need side cutters.

Nice write-up!
A lot of folks overlook this simple no-engine-running procedure. I've used it for years, just did our Silverado last week as a matter of fact. I'll be doing same to the MB sometime soon.
I've also quit using worm type clamps on anything, I much prefer the smooth bore type clamps that don't dig into the hose. Also called fuel injection hose clamps. They look better too, a minor detail but a benefit.

Will steering wheel turn without engine running? It won't lock?

Mud: Thanks! This method definitely makes a full flush much simpler. I hadn't heard of bore type clamps before, I'll have to keep them in mind. I don't mind using oetiker clamps when accessibility isn't a problem but otherwise I reach for my trusty bag of high quality ABA clamps.

Stuttgarten: You know, I expected it to lock up, but it didn't. I'm guessing it had something to do with the wheels not offering any resistance. If it does end up locking on you, you can just turn the key to something like position 2.

Thanks, I did a similar procedure a couple of years ago on my 2008 Volvo XC90. I am coming up on 100k and eight years so P/S fluid flush is one of my projects.

Ah nice, the first time I did it was on my '04 XC90 T6. The reservoir setup made it stone simple! I had the same handle on Swedespeed.

Thank you for a nice write up.
Used this to change my PS fluid , bought 3 liters from rockauto of Pentosin chf 11 s fluid.
1. i started seeing new clean fluid coming out at the end of 1 liter , but i kept going , so at the end i have half a 3rd bottle left.


2. i used a metal clamp from depot , took longer to tighten that the PS fluid flush lol (mostly because it was an awkward position and was missing some tools)



otherwise a pretty straight forward guide. thanks.

btw auto stores have this Pentosin for 26$ a liter i found it on rockauto for 13$ took a couple of days to receive but i was not in hurry.

p.s. yes once you get both wheels of the ground you can easily turn the wheels.

Great write-up... I'll add that replacing the P/S reservoir would be a smart thing as you approach 10yr/100k. The reservoir has built-in filter and here's what mine looked like at 10 years and 100k:

https://mbworld.org/forums/attachmen...1&d=1620614215

https://mbworld.org/forums/attachmen...1&d=1620614215

https://mbworld.org/forums/attachmen...1&d=1620614635

https://mbworld.org/forums/attachmen...1&d=1620614635

I sourced a replacement reservoir from FCP who sold it as OEM, sure enough its a ZF unit with the MB star ground off (1/3 price of OE). A suck 'n fill at 50k and again at 100k with a reservoir replacement would be a good strategy.

Good call, that filter looks...like it was doing its job! Appreciate the pictures. I actually replaced my pump recently and did the same thing. I used Pentosin 11S this time around. Other than getting the rear bolt in and out :X it was a breeze.

As you can see, it had been leaking for a while.

https://cimg7.ibsrv.net/gimg/www.mbw...af4fd0ea7b.jpg

Surprisingly, the original pump wasn't a Bosch like the one I got from FCP

https://cimg0.ibsrv.net/gimg/www.mbw...a30d08859b.jpg
https://cimg1.ibsrv.net/gimg/www.mbw...5b5c110561.jpg
https://cimg3.ibsrv.net/gimg/www.mbw...5ed108fe2a.jpg

Hi all, this might be a stupid question but i am relatively inexperienced at this kind of stuff. Why would the return line go to the radiator? Wouldn't it pump back into the reservoir? Do ALL mercedes have the return line attatched to the radiator? I also have a w212 E350.

It goes into the radiator because it acts as a steering fluid cooler, just like with the transmission. It then goes from the radiator to the reservoir. I think pretty much any moderately modern car has a cooler for the steering fluid.