ericycle

The car in question is a 2006 C200 CDI (OM646), currently at about 340k miles.

My service booklet does not indicate anything regarding the PS fluid, neither when it should be changed, nor to what.

The fluid is now a strange brown-gray color, and I suspect it might have never been changed in all the 340k miles.

The only symptoms are a noise when turning the wheel left/right all the way, and sometimes when turning the wheel at slow speed (and giving just a bit of gas) when the car is cold. But really it happens very, very rarely.
Also, the wheel feels rather heavy (especially after driving a rented Chevy Cruze for a week on vacation), but I understand it was designed to be heavier?

My questions are:

• Is it even ever really necessary to change the PS fluid?
• If so, why doesn't my service booklet specify anything?
• Would changing the fluid be good in terms of preventative maintenance?
• And perhaps it could make the steering a bit easier and elimate the occasional noises?
• Most importantly, what is the correct PS fluid I should use?

From the research I've done, I've learned that although MB booklets sometimes specify the use of MB part # Q 1 32 0001 (green Pentosin CHF11S), it is only needed for cars with hydraulic suspension, which mine isn't. And the other PS that supposedly applies is: 000 989 88 03 / Q 1 46 0001, which is also compatible with Dexron III. Is this correct and can I use something Dex 3 compatible?

But more importantly, if I'm going to use the simplest method of siphoning it out with a turkey baster, and I'm not sure what fluid was there originally, and I add Dexron III, could the mixing of the old and new fluids cause a problem?

Thanks a lot!!

RCPDesigns

You do not need the Pentosin. You can get the Febi/Blisten off eBay, Napa, etc. http://www.ebay.com/itm/Mercedes-Bil...-/350603702612

I got two liters from Napa. They were pretty cheap and had them in stock. I bought a simple siphon ($5) and used that to drain out the fluid. That worked really well. The hose is long enough to stick in the reservoir and have the bulb (drain side) well out of the engine compartment . Drain the fluid out, fill to the minimum level. Leave the lid off the reservoir . Turn key to first setting (don't start the car) and with wheels off the ground turn the steering wheel lock to lock a couple dozen times until no more air comes out. Look through the windshield (under the hood) and watch the level rise and fall as you turn the wheel. You'll see the air come out as well. I put a towel around the reservoir to catch any overflow which was helpful as it did overflow a couple of times. Once system is bled, check the level again, add/remove as needed, replace lid. Drive around some to work the fluid around. You can then repeat... drain out the fluid, refill, bleed, drive, etc. Do this until the fluid you drain looks like the new fluid.
You can search the forum and find a better way of doing this by removing a hose from the bottom and draining the fluid instead of returning it to the reservoir. While the route I went took more time and ultimately doesn't flush the system as well, it is pretty much foolproof and certainly got the job done.
Steering was noticeably easier, smoother and silent after the flush.
Best of luck!

wvadam

Does the booklet tell you the capacity? I have wondered this.

Regarding the fluid, I went to the dealer 5 yrs ago and they charged me $40CDN for 1 liter of the fluid. I asked the guy if there was any other fluid I could use instead and he hesitated and talked his way around the question as if the dealer had told him not to answer this type of question. Im sure there must be a cheaper kind of aftermarket fluid that can be used but I don't know what that would be.