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Discussion Starter #1 (Edited)
So I'm getting ready to do this in the next few days. I've got the filter and some plain old dextron III atf, but there's almost no info out there in the manuals or on this foum about the procedure. I read the diesel giant post on the subject:
Mercedes Power Steering Fluid Service

But is that really all there is to it? It seems like sucking out the contents of the canister would only remove a minority of the fluid in the system, like trying to change your coolant by removing the contents of the clear expansion tank. This method doesn't seem "by-the-book," but is it good enough?

Also is there any need to "burp" the system after the procedure? If so, what's the best method? Do I need jack stands?

The diesel giant pictorials are kind of nice but he always seems to leave out half the details to get you to by one of those wildly overpriced DIY videos he sells. I'd rather ask you guys.
 

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The best way is to pull off the low pressure return line going to the pump and route it to a bucket/pan. Remove the lid of the pump, remove old filter. Start the car. The fluid in the pump will quickly drain into the bucket. Do not let the pump run dry, refresh the fluid continuosly while the car is running. Move the steering lock to lock. 1-2 quarts (maybe 3) of fluid used during this process should be enough. Reconnect hose, install new filter, top off fluid.

tips: it helps to have the car on jack stands. it helps to have help. have your 2 quarts of fluid open and handy when you start the car. a larger diameter hose can be slipped over the return hose to help extend the lenght so that you can route it to a bucket. if you are going to bother with this procedure, at least use good fluid to flush & refill. I've been using amsoil ATF. the low pressure line is the one without the crimped fittings (those are the high pressure supply lines), it attaches via standard hose clamp.
 

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I did this without having the engine on. Car was on jack stands so was easy to turn lock to lock. Fluid still came out double quick. I used power steering fluid though.

Curious if much was missed by not having the pump running...
 

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My experience with this is that the fluid comes out so fast that I cannot keep up with it pouring frantically into the reservoir. Next time I do it I am going to restrict the return hose with a clamp of some sort so that I can keep up with the beast.
 

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I also checked out the dieselgiant tutorial... but I have an earlier model. Anyone know how to remove the power steering filter in the older models as it is pictured here you can see there is no nut to remove to release the spring on the filter


<a href="http://s103.photobucket.com/albums/m147/jtwangler/?action=view&current=misc017-1.jpg" target="_blank"><img src="http://i103.photobucket.com/albums/m147/jtwangler/misc017-1.jpg" border="0" alt="Photobucket"></a>
 

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That star washer on top of the spring is just compressed on. You should be able turn it left and right with your fingers while pulling straight up. Then pull the spring out and pull the filter out using needle nose pliers in the holes.
 

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Discussion Starter #10
1) Firing the engine up sounds a little scary but I'm sure it's the best way to clean all the old stuff out. Is it enough just to have it on for 3 or 4 seconds? Long enough just to turn the wheel back and forth one time? And when you say "keep the pump from running dry," do you mean I'll need to keep a few inches of standing fluid in there or just make sure there's something pouring in while it's empty?

2) And I have a feeling I might be re-starting an old forum debate here, but what do you mean by "good fluid"? I've got a bunch of Castrol Dextron III sitting around that I'd intended to use, but some have said that although these cars originally called for ATF, modern ATF has too many additives and one should therefore use PS fluid. Anyone have some concrete thoughts/experiences regarding this? It sound a little fussy to me but I wanted to check.

3) And lastly, burping the system afterward? Do I just crank the wheel back a forth a few times with the cap off the pump and the engine running?

Thanks folks.
 

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Discussion Starter #11
Update- I finally got around to doing the above flush and the positive difference amazed me. Anyone who hasn't done this definitely should! The stuff coming out of there was black sludge, and my steering (which used to moan and creak quite often and loudly) has never been quieter or smoother. Truly the diesel giant method (linked above) wouldn't have done half as much; the stuff up in the pump reservoir was cloudy but not horrible, unlike what blasted out of the return hose. Speaking of which, tuck that hose into the opening of an empty gallon jug to avoid a splattering mess- really helped me out. Anyway try it out!
 

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I did this without having the engine on. Car was on jack stands so was easy to turn lock to lock. Fluid still came out double quick. I used power steering fluid though.

Curious if much was missed by not having the pump running...
This is an interesting post as I was going through some youtube videos on this and found that most of the guys flushed oil oil by turning the steering wheel with the engine dead.


But when it comes to Older MBs they all resources on the web seem to indicate you must run your engine to do this?

Is this just another way to do it by not running the engine? What are the pros cons...(some oil left but no pump damage...)

I am just trying to evaluate what is the best method to do this on my Brynhildr?
 

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Have a helper.

I opened the low pressure line and with a container ready, let the fluid dump in that.

Have a gallon of power steering fluid open and ready to add to the reservoir.

Have your helper start the car. Fluid will come out fast. Keep the reservoir topped up until you see clear fluid coming out, power steering fluid is clear, so an easy observation.

I did this with the old filter in place. After the above procedure, replace the filter. With the engine off, turn the steering wheel side to side, you'll note air bubbles for a while, once no more appear, install new filter, top up the fluid and button everything up.
 

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...

But when it comes to Older MBs they all resources on the web seem to indicate you must run your engine to do this?

Is this just another way to do it by not running the engine? What are the pros cons...(some oil left but no pump damage...)

I am just trying to evaluate what is the best method to do this on my Brynhildr?
I totally disagree with doing this - particularly the draining of power steering fluid (is anyone daft enough to do that?) with the engine running. It is totally unnecessary to have the engine running for either draining or filling.

This is what I do =>

1) Turn the wheel all the way to the left



(This is for a left hand drive vehicle - there is a slight possibility that you need to go the other way - all the way to the right for a right hand drive vehicle - assuming the box is built the other way round)

2) Undo the centring bolt on the bottom of the steering box



The oil will then pour out of the whole system

You don't have to arse about with turkey basters or undoing pipes or anything like that.

Doing it this way is the best way because (something like) 99% of the oil in the system is drained.

PeachParts Mercedes ShopForum - View Single Post - What a feeling it will be! A properly adjusted W123 / W116 / W126 power steering box

For filling

1) stick the front wheels on slip plates

OR

raise the front wheels off the ground

2) Put that bolt back in!



3) Replace the filter!

Don't be tight

4) Put in new clean Dexron II ATF (Dexron III if you can't find the 2)

5) Fill from the top of the pump

6) Turn the front wheels from lock to lock - NO engine power required!

7) Keep adding fluid and turning the steering wheel from lock to lock until the correct level is achieved.
 

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^ I'm sure that'll work fine and the OP is interested in finding as many ways of doing this as he can get.

I have performed this procedure (as stated above), with the car on the ground, a number of times, no ill effect.
 

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I totally disagree with doing this - particularly the draining of power steering fluid (is anyone daft enough to do that?) with the engine running. It is totally unnecessary to have the engine running for either draining or filling.

This is what I do =>

1) Turn the wheel all the way to the left



(This is for a left hand drive vehicle - there is a slight possibility that you need to go the other way - all the way to the right for a right hand drive vehicle - assuming the box is built the other way round)

2) Undo the centring bolt on the bottom of the steering box



The oil will then pour out of the whole system

You don't have to arse about with turkey basters or undoing pipes or anything like that.

Doing it this way is the best way because (something like) 99% of the oil in the system is drained.

PeachParts Mercedes ShopForum - View Single Post - What a feeling it will be! A properly adjusted W123 / W116 / W126 power steering box

For filling

1) stick the front wheels on slip plates

OR

raise the front wheels off the ground

2) Put that bolt back in!



3) Replace the filter!

Don't be tight

4) Put in new clean Dexron II ATF (Dexron III if you can't find the 2)

5) Fill from the top of the pump

6) Turn the front wheels from lock to lock - NO engine power required!

7) Keep adding fluid and turning the steering wheel from lock to lock until the correct level is achieved.
Thanks a lot Stretch! I must admit this looks like a much better and neater way of flushing the system...I was looking at all those power steering flush videos and resources on the net and wondering that on such a well thought out car why would Mercedes not think of a way to do power steering flush and you have provided the perfect answer.
 

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Thanks a lot Stretch! I must admit this looks like a much better and neater way of flushing the system...I was looking at all those power steering flush videos and resources on the net and wondering that on such a well thought out car why would Mercedes not think of a way to do power steering flush and you have provided the perfect answer.
I think the way I have explained is the best way to do the job - this however, is not the way Mercedes say to do it. They expect you to arse about with syringes and the like. In this case I don't think the people who were writing the maintenance manuals were aware of the ability to drain via the steering box.

The W201 version of this steering box, for example, is positioned at an inconvenient angle to do this trick. It just so happens the W123 chassis is made in such a way that this works.

I am convinced (after taking several W201 and W123 steering boxes to pieces) that draining from the lowest point in the system is the best thing to do. All of the muck and junk in the fluid eventually settles in the bottom of the steering box - and some of it must be abrasive (metal) which will eventually speed the delicate parts of the steering box to the great scrap yard at the bottom of the hill.
 

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I'm with Stretch... I do all my cars the way Stretch does at about 5 year intervals ...I don't put that many miles on the cars (maybe 3-4K per yr. ea.) so its easier for me to just do them all at the same time.
 

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How about modern Power Steering fluid instead of the Dexron which is really a ATF?
I'd stick with ATF - it is also used in manual Mercedes gearboxes and there it really makes a difference. I'm not so sure if the steering boxes and the steering pumps are as fussy. If you do switch from something to something else make sure you don't go from a fatty oil to a mineral oil or vice versa because the seals can get eaten by the new oil type. Then you end up with a power steering watering can system!
 
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