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Changing power steering fluid and reservoir w212 E350 CDI

MrGreedy

MB Enthusiast
Joined
Jan 13, 2020
Messages
2,807
Location
Here and there
Car
E350 CDI
This is more of a brief how to than anything else. Learned a few things that will help anyone wanting to try this.

It was a pleasant 7⁰C this evening, so positively tropical to be doing this on the drive in the light drizzle
:cool:

New reservoir was £48 inc VAT from local dealer. Had to order it in so took a couple of days.

PAS fluid is Merc 345.0, which I suspect is just Fuchs Pentosin CHF 11 in a Merc bottle. Opie oils was cheapest. I suggest 3L.


Other things needed:
- Torx star bits to remove air filter.
- E10 torx socket.
- Junior hacksaw/blade.
- 15-17mm fuel hose clamp.
- Angled hose clamp pliers (you can manage with a very small pair of mole grips, but it will take you forever due to lack of space and you will wish you had spent £8 on some angled hose clamp pliers.
- a couple of empty 4 pints plastic milk bottles.
- an empty bean/soup etc can.
- 10mm ID silicon tubing and a 10mm OD small piece of plastic tubing.
- assorted small zip ties.

Remove engine cover.

Unclip the batwing on the passenger side and remove the air filter.

Using E10 torx socket remove bolts from the air box and remove all the passenger side air box pipework to create more room.

For the return fluid pipe at the front of the PAS reservoir, you need to get the metal clip off. For me, the access to undo the clip was underneath the pipe with little access. I didn't mess about and started to cut through the securing nobble on the clip with a junior hacksaw. Rags underneath to catch swarf. It didn't put up much of a fight and soon popped off. On reassembly, I used the 15-17mm fuel hose clamp, which went back of easy and is a breeze to tighten and remove again should that ever be required.

Put the empty can under the return pipe inlet for the PAS reservoir, the one you've just removed the clip from.

Pull the pipe off (it comes off very easily, and let everything drain out of the reservoir and the pipe you've just disconnected into the conveniently positioned can. It lodges perfectly in place 👌


Screenshot_20241210_001114_Gallery.jpg
 
When fluid is all drained,
Remove the three torx bolts for the PAS reservoir, which will allow it some movement.

Wrap rags all around the lower, much fatter PAS feed pipe. It's underneat the PAS reservoir, access is a pain. Make sure you have removed all the passenger air box (in the photo above, you can see a bit of the lower air box that holds the filter, and it needed to come out).

Get your angled hose spring clip pliers and release the spring clip and slide it down the rubber hose.

Give the reservoir a wiggle and a twist. You might need to slide a BLUNT screwdriver down the side of the rubber pipe to start to crack the seal. Once it's wiggling, it slides off pretty easy. Try and get a small rag over the reservoir outlet to minimise spillage of any remaining oil.

Fit the new reservoir, but block the return feed. Here, I used a short piece of 10mm ID silicon tubing, cable tied on to the reservoir inlet and the other end of the tubing had a smooth jelly bean shaped pebble jammed in the end and cable tied into it to block it (heading off in the direction of the screenwash fill neck in this photo)
😅

Screenshot_20241210_002520_Gallery.jpg
 
Get another length of 10mm ID silicon tubing and a small length of 10mm OD had plastic tubing, and cable tie this from the outlet/return power steering pipe, and heading into a plastic 4 pint milk bottle, which really conveniently fits securely in the space where some of the air filter has been removed.

Top the PAS reservoir up to the brim of the next. Right to the top.

Jack up the car at the front to lift the wheels off the ground.

Turn the steering lock to lock, which will expel a small amount of fluid into the plastic milk bottle fluid dump as you get towards the end of the full lock. I found doing two full locks removed what felt like a sensible amount of fluid, based on what I needed to top up. So, all the way from e.g. full right lock to full left lock, then back to full right lock.

Go and top the fluid up to the brim.
Repeat the turning lock to lock twice.

I chose to buy 3L of fluid. I repeated the lock to lock top up process many times until I was just over 2L through. The fluid still wasn't pristine at this point.

Place the bean can under the reservoir again, and disconnect the silicon tubing from the reservoir and the return feed tube. No need to let all the fluid drain. Just get the return hose back on to the reservoir, not forgetting the fuel hose clamp.

Remove the bean can. Tighten up the fuel hose clamp. Wipe everything down.

A bit at a time, carefully top up the reservoir, checking fill level with the dipstick.

When you get to around the 20⁰C max mark, do a couple of lock to locks again and recheck level. I needed to top up a little bit.

I then started the engine and left it running for a minute, and then did another couple of slow lock to locks. Turned everything off. Removed jack. I then needed another tiny top up to get half way between 20⁰C min and max. It was 7⁰C, so I'll check it again when I have time to get temps as per those stated on the dipstick (which is integrated into the PAS reservoir lid).
 
All the above information is just how I tackled it. I'm not a trained mechanic. Don't rely on my method without doing your own research first.

I'll cut open the old reservoir another day and take a photo to see how much crud is in there.

The fluid was very dark, just like the photo @W1ghty showed in his PAS fluid replacement thread. Which gave me good inspiration and ideas for tackling the E350.
 
Another couple of useful bits and pieces:

When removing the air box (that holds the filter), once you've removed the two securing torx bolts on top, the air box pulls upwards. The bottom of the air box has two plastic studs pushed into two rubber bungs/holes. It just requires some firm wiggling to free it off.

Looking at the Merc approved fluid, there is only one that Merc themselves have approved. It's the Fuchs fluid, as set out in the link I provided in post #1. I picked this up around £12 a can on Black Friday discount. There are other fluids that the fluid manufacturers claim meet MB 345.0 spec, but the Pentosin CHF 11 is very likely to be the actual fluid Merc use and is pretty much as cheap as the fluids that aren't approved by Merc.

If you are buying an E10 torx socket for this, if you have a choice, buy a 1/4" drive socket. This is because the access for the torx socket at the back of the reservoir is very tight, and my 3/8" torx socket/extension was pressing against the side of the reservoir, making cross threading of the retaining bolt a real risk on reassembly (disassembly was fine). I took a bit of time making sure it wasn't cross threaded before using my ratchet to tighten, but I was wishing I had a 1/4" drive. In fact thing about it, I could have used my 3/8" drive E10 torx socket, then an adapter down to 1/4", then my 1/4" extension up to my 1/4" ratchet.

The angled hose clamp pliers look like this. I can't recommend enough getting some for this job.
us-pro-angled-hose-clamp-pliers-5860-tools-2u-direct-sw-3_1024x.jpg


On the top of the reservoir there is a little push mount for a cable tie that holds some electrical flex. I just cut the very small cable tie with some wire cutters to free the cable. I didn't have a new cable tie mount, and the old one didn't look like it would easily come out of the hole in the top of the reservoir, so I just snipped the top of the reservoir to release the cable tie mount and then reused it.
2056943-jpg.jpg


W1ghty's thread:

 
That was one hell of a diy write up buddy , really top job !!
This should be placed in the DIY section as a sticky .
 
I bought a pack of these to block off pipes , saw them on a YouTube vid. I used them for blocking brake lines when I changed calipers or brake rubber hoses but they could be used on any smaller pipes
 
So, taken the Merc for a couple of short drives. About 15 mins max each.

I thought it best that I checked the PAS fluid level, and it wasn't touching the dipstick (although the min to max is a tiny quantity of fluid.

I could see the fluid level in the reservoir tank, peering in with a torch, but obviously not enough to measure with the dipstick. A couple of tiny top ups (maybe a table spoon each) and it was back to mid way between min and max. It's another 7⁰C outside, so this is fine for now. One day, I hope it will be 20⁰C again outside so I can check the levels at the correct temperature, although the lack of seeing the sun for what feels like weeks now makes me wonder....
 

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