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Meles · 03-31-2008, 04:32 PM

I'll start with a general post for mercs and then my notes from doing 1993 300sd. This is a nice link describing the procedure on a typical Mercedes:
MercedesShopWiki: Power Steering Filter Change and Fluid Flush

I've read up and I would definitely use Mercedes official power steering fluid. I did this job because mine was low and I had added Valvoline stopleak power steering fluid from autozone (they checked their fluid hotline and said anything standard was fine, not stuff for Hondas.) I searched a little and everyone coughs up for Merc fluid and that is what the OEM sites sell (Autohauz), so I decided to flush.
For w140 there is no room for a jug next to the return hose per procedure. I found a T (with a cap at autozone) for the half inch hose and bought another length of hose to connect and get out to jug (got a 4 pack of clamps). You'll want to have a battery tester (a large turkey baster you can buy at autozone) to drain the reservior. You'll want a little shallow margarine container for when you disconnect return hose so you can catch what dumps out of reservior. I went ahead and pulled the filter so I could turkey baste out almost all the reserviou. A nice size rag would work in place of container. You probably can leave the filter out for flushing since you will be pouring clean into the reservior. Once you have return hose in place you are ready to go.
You must have two people. The fluid will drain really fast so have your bottles open and turn that wheel lock to lock while doing this. Have things layed out nicely so you don't start knocking over containers and pulling the hose out of your jug. I used cheapest fluid from autozone which was clear. I then followed with one quart of the Merc fluid. (Might be nice to have a clear half inch drain hose (Lowes) to watch the fluid go clear with cheap stuff and then back to amber with the final quart flush with merc fluid, don't know if pvc tubing at Lowes would work or just leak.) As the fluid runs low you will not be able to turn wheel and you will hear creaking before this. Proceed and drain all fluid. Reconnect everything and add your merc fluid per procedure.
Things were foaming coming out during the flush and then as I added. I had extra fluid so I basted out some of the foamy solution in the reservior. It would probably disipate with time as you let it run for a while. (Foam probably from air in system as it went low at end of flush.)
My fluid looked like used motor oil (not diesel used though) and probably had not ever been done in the car's 250k miles.
My assembly probably has been leaking for a long time. Back 4 years or so a new mechanic wanted to replace it where I go and the owner said it is a waste as merc pump/stearing box like to leak a little bit. Mine probably had not been checked in the 100k I'd had it (easy to check, just unscrew and make sure between min and max.) I noticed funky steering sound in snow and checked (it was about an inch below min.)

03-31-2008, 04:32 PM	#107 (permalink)
Meles BenzWorld Member Date registered: Jan 2006 Vehicle: 93 Mercedes 300SD Posts: 52	Power Steering Flush I'll start with a general post for mercs and then my notes from doing 1993 300sd. This is a nice link describing the procedure on a typical Mercedes: MercedesShopWiki: Power Steering Filter Change and Fluid Flush I've read up and I would definitely use Mercedes official power steering fluid. I did this job because mine was low and I had added Valvoline stopleak power steering fluid from autozone (they checked their fluid hotline and said anything standard was fine, not stuff for Hondas.) I searched a little and everyone coughs up for Merc fluid and that is what the OEM sites sell (Autohauz), so I decided to flush. For w140 there is no room for a jug next to the return hose per procedure. I found a T (with a cap at autozone) for the half inch hose and bought another length of hose to connect and get out to jug (got a 4 pack of clamps). You'll want to have a battery tester (a large turkey baster you can buy at autozone) to drain the reservior. You'll want a little shallow margarine container for when you disconnect return hose so you can catch what dumps out of reservior. I went ahead and pulled the filter so I could turkey baste out almost all the reserviou. A nice size rag would work in place of container. You probably can leave the filter out for flushing since you will be pouring clean into the reservior. Once you have return hose in place you are ready to go. You must have two people. The fluid will drain really fast so have your bottles open and turn that wheel lock to lock while doing this. Have things layed out nicely so you don't start knocking over containers and pulling the hose out of your jug. I used cheapest fluid from autozone which was clear. I then followed with one quart of the Merc fluid. (Might be nice to have a clear half inch drain hose (Lowes) to watch the fluid go clear with cheap stuff and then back to amber with the final quart flush with merc fluid, don't know if pvc tubing at Lowes would work or just leak.) As the fluid runs low you will not be able to turn wheel and you will hear creaking before this. Proceed and drain all fluid. Reconnect everything and add your merc fluid per procedure. Things were foaming coming out during the flush and then as I added. I had extra fluid so I basted out some of the foamy solution in the reservior. It would probably disipate with time as you let it run for a while. (Foam probably from air in system as it went low at end of flush.) My fluid looked like used motor oil (not diesel used though) and probably had not ever been done in the car's 250k miles. My assembly probably has been leaking for a long time. Back 4 years or so a new mechanic wanted to replace it where I go and the owner said it is a waste as merc pump/stearing box like to leak a little bit. Mine probably had not been checked in the 100k I'd had it (easy to check, just unscrew and make sure between min and max.) I noticed funky steering sound in snow and checked (it was about an inch below min.) __________________ 1993 300SD, 250,000 miles and counting Car burns a quart every 600 miles which apparently is the norm and has been the case since I got it at 145,000. Many tricks to these. Ask. I've learned the hard way.