I just accessed my 2009 C30's power steering reservoir as my steering has been making a "groaning" or "howling" noise (not very loud, but noticeable while driving) during low speed turns like into a parking spot.

I can only see into the reservoir vertically - there's no way to see the "fill" lines on the outside of the reservoir. It looks like there's a nut inside the reservoir (see pic attached: sorry for the poor quality) so I'm assuming its low.

How do I know how much fluid to add?

 

if on full lock then they all make a bit of noise , but if noise all the time then check for leaks around the steering rack , its a closed system so if the fluid drops then you have a leak , and needs to be fixed ,adding fluid will not help the seals on the rack are no good , if its an old car one can add leak seal which helps the seals for a while untill it needs a rebuild

 

Thanks for the reply. It doesn't make the noise all the time - just once in a while at low speeds and turning, like into a parking space. Even then, some days it will do it, and some days it won't.

It is a 2009 and I just added some Bar's Leaks power steering additive, so we'll see what happens from here.