[W126 Coupe] Power steering fluid

[Dick Spellman]

Mister McGoo wrote:

> If one does not have access to MB Genuine Power $teering Fluid, does 

> anybody have any recommendation for a compatible top-up?  Comments?

>  

> -Bellamy

>

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Hi Bellamy,

If it's just topping off, then Febi is recommended.  I have no 
experience with Mobil1 PS fluid but, have been running M1 engine oil for 
years so I'm sure it's a good substitute.

If you are looking to remedy the groaning that can develop on these 
pumps, I'd use Pentosin CHF 7.1.  Jonathan helped me through this 
constant groaning experienced on the M103 power steering pumps both with 
original and topped off MB PS fluid in two 300SE's.  He recommended I 
hunt down Pentosin CHF and then remove the filter, drain the sump, 
remove the return line and carefully flush the entire system that 
included the lines and the steering box.  I did this by adding fresh 
Pentosin to the sump absent the filter, then briefly cold cranked the 
engine until the sump level went low. Being careful not to run the pump 
with no fluid (air only).  The return line was spewing old dark colored 
ps fluid into a container set up on the floor.  I did this and after 
1.25 qts of expensive Pentosin finally had a fresh stream of PS fluid 
(Pentosin is Green) exiting the return line.  (Jonathan recommended I do 
the sump several more times after the line went clean, but, I stopped 
sooner as this stuff is very expensive.  I think it's $15-17 per qt and 
I started with 4 qts.  Button everything up, add the new filter and top 
off with more fresh Pentosin.  I used a total of 3 qts on two MB's and 
have 1 spare qt for routine filter and topping off maintenance in the 
future.

No more groaning on either MB 300SE.  It's probably worth noting that 
the usual maintenance of sucking out the sump when replacing the filter 
did not work which is why I resorted to this more thorough flushing and 
replenishment Jonathan explained to me.  And, the M103 typically 
operates at a much higher rpm than the V-8's.  For example, at speeds of 
60-70 you see rpms of 3000-3500rpm as normal.  So, the pumps get a much 
harder work-out on M103's than they will on the V-8's IMHO.

Take care,
Dick
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