Larry1979

Gentlemen I have a question for the group. Does the fluid in the Power Steering System ever mix with the fluid in the ABC System since both systems share the same pump?

I have a 2011 S63 AMG and I ask because I had my power steering i fluid flushed today and the dealer originally said that I needed Pentosin which is what I was tracking I needed, however, they came back and said that they ended up using the regular MB Power Steering fluid because the fluid that came out looked like regular MB Power Steering fluid. I was uneasy about their decision to use regular MB fluid although they assured me that there would be no issues. I have been reading up on this ever since I returned from the dealer and everything that I've read says that the fluid should be Pentosin. I know how delicate the ABC System is and I just had the ABC fluid flushed and filters changed a couple of weeks ago and I want to ensure the regular Power Steering fluid is not going to contaminate the ABC System.

Should I have the Power Steering fluid drained and add Pentosin or will it be ok like the dealer told me?

Welwynnick

Don't worry.

The PAS and ABC fluids never mix - same pump, two completely different systems.

The PAS system can use either ATF or CHF, and the only way to find what's in there is to look at it. Whatever is already in there - flush or fill with the same. Changing from ATF to CHF sounds like a very bad idea. You would never get ALL the ATF out, and CHF11S should never be mixed with anything else, except maybe CHF202.

Nick

Larry1979

Nick thanks for the reply. It is a relief to know that my ABC System will be fine because I just had the filters changed and the fluid flushed. Good to know that neither ABC fluid nor filters are compromised.

The dealer told me that although the manual calls for Pentosin, the fluid that came out of the reservoir didn't look like Pentosin. I don't know if they only went off color or if there were other characteristics of the old fluid that led to their decision to use regular power steering fluid but they said that Pentosin has a distinct look. They told me that they wanted to use the same fluid that came out. The power steering fluid has never been changed so I don't know how anything other than Pentosin could have been in there. I will take it back and have them re-flush and fill power steering reservoir with Pentosin.

Thanks again.

Larry

pumpedTSI

Just a side note.....before I changed my ABC system from Pentosin to Mobil 1 ATF I did a little test.....I mixed both 50/50 in a glass and let sit for a week....no curdling or separation so both are compatible and should not cause issues. I wuld however flush and fill with one or the other....my choice would be Mobil 1.....

Larry1979

Thanks for the info. I just changed ABC fluid and filters using Pentosin a few weeks ago. Unfortunately my dealer put the regular non-synthetic power steering fluid in yesterday and I'm going to have them re-flush and fill with Pentosin.

Welwynnick

I really wouldn't change the oil, but it's your car.....


Nick

syljua

Nick, you are obviously *the* resource on ABC here, but are you completely sure of that? Some StarTuned articles seems to indicate that the fluid is shared;

https://www.mbwholesaleparts.com/dow...eBaselines.pdf
and
https://www.mbwholesaleparts.com/dow...Suspension.pdf

Could that be a difference between 220 and 221 ABC? Or are the StarTuned articles too vague in their description? (two chambers in the reservoir?)

I have to underline, that I do not know. Just want to learn

br,
syljua

Larry1979

I was provided additional information by other members of the forum that indicate that the two systems are separate although they share the same pump.

syljua

Care to share?

br,
syljua

syljua

Yes, I think the first 2 StarTuned articles I referred, were too unclear on
the fluid sharing. This one does mention 2 reservoirs;
https://www.mbwholesaleparts.com/dow...1/MBST-ABC.pdf

Also comparing to the information and image of the reservoir(s) here;
http://mercedes-abc-drive-carefully....y-part-of.html

br,
syljua

Larry1979

http://mercedes-abc-drive-carefully.blogspot.co.uk/2014/08/overview-abc-system-isthe-key-part-of.html

“The power steering and ABC pump are integrated into one unit, referred to as a Tandem Pump. Although the two pumps share the same housing, they are separate components otherwise.”

Looks like the second article that you posted is the same one I referenced as well.

Welwynnick

I'm not sure what you're saying here:

In this post you suggest that the PAS fluid was topped up with ATF, and is presumably separate to ABC:
And here you suggest that they're the same system:
I'll freely admit that I don't know as much about the W221 ABC system asI do about the W220, but I do have SDS, WIS and EPC, so I looked at a lot of W221 documents. It appears the two cars don't share any ABC components, but the architecture is much the same.

ABC is a storage system where the pump works at low flow and high pressure all the time the engine is running, and fluid is tapped off by opening a valve to meet demand. Power steering systems are completely different. They work at low pressure while the engine is running, and raise pressure by closing a valve on demand. This is wasteful of pumping, and ABC has to be more efficient because of the much greater peak power requirement. They're fundamentally different systems that are quite incompatible. Few people realise the distinction.

The W216/221 and W215/220 both have a tandem pump and separate hydraulic systems. The 221 pump has an integrated accumulator, and the W220 does not. The 220 has an irregular shaped PAS reservoir, and the 221 is sort of cylindrical, like many other cars. You can check this by looking under your hood. The W221 ABC reservoir is part no A2213200214:



while the PAS reservoir is part no A2214660102:



Well, the StarTuned articles are wrong about something as simple as the fluid reservoirs, so it makes you wonder what else they have wrong (and there were a few things that stuck out immediately). They're written in a peculiar way, like they're trying to show off how much they know (which has backfired) while not being informative.

I think ABC and PAS could share a fluid reservoir in principle, but MB have chosen not to do it, presumably for redundancy. It has to be a tandem pump either way, though.

Nick

Larry1979

Nick I did state that I believe the dealer put the wrong fluid in my PAS reservoir and I am 100% with you amd agree that the systems are separate. I was mainly concerned as to whether the fluids ever mix and you answered that for me.

The STAR info that suggested that the systems were one in the same was provided by a different poster.

Larry

syljua

Please note, that I was just chiming in on Larry1979 OP, and him and I are not the same person...

br,
syljua

Welwynnick

Oops, sorry guys.

Nick