I'm about to replace my leaking low pressure return hose, so this would be a convenient time to replace the power steering fluid. (It's dirty; probably hasn't been changed in 145K mi.)

I'm familiar with the flush procedure, but I wonder whether it would be better instead (or in addition) to drain the old fluid at the lowest point in the system, which would be 'A' in the photo below. But before I do something stupid, can anyone tell me whether this plug, with a reverse Torx head, is a proper drain?

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Is that where the pinion sits? If so, do not touch that bolt!

I am curious about this too. Mine has not been changed and doing so would be good preventative maintenance.

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raMBow

1999 E300DT Obsydian Black Metallic, Heated Full Leather Parchment options, E2, K2, 136,000+, best 36.5 mpg - GP's 12-04 & 11-12 Zero Stuck
2010 Honda Odyssey - The BrideMobile - best 26.5
(2) 2005 Honday Accord- (1 -Corporate 1 - Personal) - 110,000 4-cyl 30mpg
2000 VW Golf GLS TDI, Upsolute Chip (sold to Brother, now 300+k on it) 48.5 mpg like clock work
1987 Honda CRX HF - Sold 87,000 always over 50 mpg Max 67 mpg

I took about 20 minutes, and didn't find an answer in my "STAR Classic Service manual library".

I know these cars are supposed to have PS fluid filters. I just don't know where they are.

So.. having said that... I'm ASE certified, and dont' know the answer. I guess I need more MB experience.

I'd say for now, get out the turkey baster, and drain, fill, run for a minute and repeat until your happy.

Certainly, I will confirm, putting a wrench on that pinion bolt would be wrong.

the 98/99 for sure does not have a replaceable filter. One is shown on many parts house parts lists oftentimes but is an error.

to my knowledge there isnt a drain plug either.

Would be surprised if the 96/97 had either one as well.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Seems like I recall that the ps tank has a filter integrated into it. So if you want to replace it you have to get the entire black plastic box.

Keep in mind this is total recall only.

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raMBow

1999 E300DT Obsydian Black Metallic, Heated Full Leather Parchment options, E2, K2, 136,000+, best 36.5 mpg - GP's 12-04 & 11-12 Zero Stuck
2010 Honda Odyssey - The BrideMobile - best 26.5
(2) 2005 Honday Accord- (1 -Corporate 1 - Personal) - 110,000 4-cyl 30mpg
2000 VW Golf GLS TDI, Upsolute Chip (sold to Brother, now 300+k on it) 48.5 mpg like clock work
1987 Honda CRX HF - Sold 87,000 always over 50 mpg Max 67 mpg

Any success w/ the fluid flush?

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#dieselFLEET
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'97 E300
'99 E300

I simply suction out fluid, refill with the proper fluid, drive around the block and repeat 'til I've gone thru the 1L container. I am always reluctant to un-do high pressure hoses. My crude method is effective enough for my taste. Considering that most folks never touch the fluid during the vehicle's lifetime, this is a reasonable solution.

Okay, I replaced the hose and did the flush today. Here are some thoughts:

PROCEDURE:
1. Line your work area with newspaper or other absorbent material. You WILL spill some PS fluid.
2. Move the windshield washer reservoir out of the way so you can access the return hose easily. (Mine is a '96; I understand the reservoir is a little different in the turbo models.) The hose you're looking for is the one that connects to the bottom of the black plastic PS reservoir.
3. Using a fluid transfer suction gun, turkey baster, or other device, remove the fluid in the PS reservoir and put it in a suitable container for proper recycling/disposal (check local government regulations). You'll get a little less than .25 litre.
4. Tighten a hose clamp on the rubber return hose. Loosen the 10mm bolt that holds down the metal return lines under the washer reservoir and disconnect the rubber return hose from the metal return line. (Have some paper towels in place to catch the spill.)
5. Connect a 3- or 4-foot section of 3/8 in ID rubber (fuel) hose to the metal return line and run it down under the car and into an empty 1-gallon container. Make sure the container will not tip over when fluid starts to squirt into it. (Note: I had the front of my car on jacks when I did this, based on another post that suggested the PS pump wouldn't pump as hard if the wheels are off the ground when turned. In retrospect, I don't think it made any difference, although it did make it easier to fit the 1-gallon container underneath.)
6. Fill the PS reservoir with new fluid. Get your additional containers of new fluid ready to pour (caps off, within reach).
7. Have your assistant start the engine and turn the wheel back and forth quickly while you replenish the PS fluid in the reservoir. WARNING: It will pump out as fast as you can pour it in, so be prepared to go through 2 litres in under 20 seconds! You don't want the pump to run dry, so shut off the engine before it does.
8. Reconnect return hose, remove clamp. Replace windshield washer reservoir. Fill PS reservoir. Start engine, turn wheel side to side, filling reservoir as needed. Take test drive and fill reservoir as needed.

FLUID: I used 2 litres of Febi PS fluid (about $8/litre) for the flush, then refilled with part of a third litre. The 2+ litres of waste fluid was gross. The new fluid in the reservoir is clean for now, but I expect to do this again in a year or two. An alternative approach is to use a larger quantity of cheap PS fluid ($2/quart) followed by 1 or 2 litres of Febi or MB fluid, but please be cautious. Because the fluid foams as it is pumped through the system, a 1-gallon waste container can catch only 3 quarts/litres before it overflows.

UBERWGN'S FLUID SWAP METHOD: In principle, this would be a fairly good method (it's certainly easier than the flush I described), but its efficacy depends on the percentage of the system capacity contained in the reservoir. In this case, the PS system holds 1.0 litre total, with a little under .25 litre (let's call it .2 litre) in the reservoir. If you suction/refill/drive four times, and assuming perfect redistribution of the crud each time, you'll remove about 59% of the impurities. With five cycles, 67%. I like to think the flush does better than that, but of course it's a tradeoff. If the reservoir held 50% of the system capacity, Uberwgn's method would definitely be a good choice, as four cycles (2 litres) would remove 94% of the impurities.

Let me add just a bit here. I was completely unsuccessful in bleeding all the air from the system with the engine running. Turning the steering from one side to the other with the engine off first, then running, fixed the problem (front wheels off the ground). You'll know instantly if there is any air in the rack, since you will lose the damping ability. Scary shudder.

Also, my '96 does lack a filter.

Based on my own experience with changing PS fluid, I wouldn't recommend the flush method described in several places on this board, including above. The PS pump goes through the fluid really fast and you have a really good chance of running the pump partially dry. What I have found that works really well in my opinion is to just disconnect the low-pressure hose at the reservoir, let the reservoir drain, suck out any remaining fluid in the reservoir with a MityVac, then connect the MityVac to the low-pressure hose and suck out any remaining fluid in the system. I think this removes most of the fluid from the system. After that you can replace the filter if there is one and refill the system. It's very important to bleed the system before starting the engine. Raise the front wheels and turn the wheels all the way to each side until the fluid level no longer drops in the reservoir. Then you can start the engine and repeat the wheel turning a few more times.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

draining p/s fluid does very little to flush and clean the system. pjc's method is pretty good except you really don't need to mess with adding a hose. Simply disconnect the return line from the res and snake it down so that you can lower it into a drain pan with the car flat on the shop floor. After pouring through the two quarts be ready to shut the engine off as soon as power assist ceases. This decision can be made by the assistant. As soon as they feel the steering go stiff, shut it off. You will not hurt the pump as it still has enough residual fluid to be lubricated for a minute or two and you are shutting it off immediately instead of a minute later.

The flushing procedure is the only way to go. The turkey basters and such accomplish so little that it's not worth the bother.

That's like saying draining oil from the oil pan accomplishes so little that it's not worth doing. The method that I described removes most of the PS fluid from the system without requiring an assistant or running the pump partially dry. You've obviously never changed the PS fluid on a W210. Even a few left-over bubbles in the system can make some awful grinding sounds when the PS pump starts running. The only way to prevent that is to bleed the system entirely before turning on the engine.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

A rack and pinion is a whole different ball game, but yes I have indeed flushed a few of them. In those cases you have to crack a line to bleed it sort of like bleeding injectors.

The flush method that is talked about in this thread is what I call the ASE method. The reason I call it that is this is the method in the ASE test and is widely accepted. Flushing a power steering system does a better job by at least an order of magnitude as compared to draining most of it.

Engine oil is a totally different issue. Engine oil typically gets drained and replaced often and for good reason, there are combustion byproducts and all sorts of contaminants and acids that appear in engine oil. P/S, or most any other hydraulic system for that matter, have to be flushed to remove metallic particles and oil that is tired from heat cycling. Engine oil typically gets changed for contamination reasons, not because of lack of lubrication ability.

In the case of the MB there is a filter, but most P/S and many hydraulic systems have no filter. The filter takes care of the metallic particulate, but can do nothing for the tired oil. SOooo.... following the "ASE Method" is not as important on an MB, but IMHO it is still a very good thing to do every 150,000 miles or so.

While I agree that one flush will do a better cleaning job on the PS system than one drain/suction/refill method, I still don't think a flush is a good way to go if it causes the PS pump to grind. Wouldn't you agree with that? It's been my experience with the W210 system that any air trapped in it will let itself be known through a nasty grinding noise. I have found the W123 system a lot more forgiving. I also think that if one simply replaces the fluid every 30K miles or so, then it's just as good if not better than a flush every 150K miles. I once tried the flush on my 240D after having done the simple drain/suction/refill method once or twice prior to the flush. Only clean fluid came out and I almost ran the pump dry. The flush isn't worth it IMO.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL