Steering heavier than usual

[Luk4shO]

Hi guys. I searched on countless ammount of forums and can't find an answer for my problem. Long story short, steering feels heavy. And I know it's not just in my head cause for first 20-30 seconds after starting the car it's a lot lighter and then turns heavy.
Now for some background (long story).
About a month ago after completing my journey to work (11mls one way, 90% on motorway) when revrsing into parking spot I've heard a loud whine. Since I was running slightly late I didn't think much about it. Then coming back home, towards end of my trip and being stuck in traffic I've heard it again, even with the slightest movement of the steering wheel. But seemed to go away once car fully warmed up. So I went and done some research and found out its the PAS pump making that noise and to check the fluid level. Bingo! To my surprise it was below low but still visible in reservour. So next day I went on to look for Pentosin around my town but no luck so I had to get that ordered for the following day. But in the meantime I have to admit, I had no choice but to drive the car to work (22miles combined, mostly motorway like I've said). Following day I topped up the fluid and the sound has not come back since (it only took about 150ml to get it up to max again). That got me wondering if I've got a leak somewhere but there is no obvious leaks anywhere and garage floor looks pristine. Also I regulary check the level both when car is cold and warm and it's not going down. But since that happened to me the steering has been heavier. Initially I though it was in my head but drove the car today and when I first start it, wheel is nice and light for first 30 seconds or so. Then in turns heavy. To a point where it almost feels like there is a "deadzone" near centre and then its heavy. I can feel it at standstill and any speed up to about 50mph, there is a lot more feedback from the road to the wheel. Checked the play in track ends and it's tight, no play or anything, 1mm on steering wheel and you can see wheels moving. Also, everything I've said aboe aplies to Comfort mode. I can also feel that steering assisstance works, when I switch from comfort co Sport or Sport+ it does have an effect. It's kind like Comfort is as stiff as Sport now at speed and Sport+ when moing really slow (parking lot etc). I think I should also add that the car has 77k miles on it now and PAS fluid has never been changer. I've syringed some out and it looks kinda cloudy greenish gray.
So my question is, what is most likely causing the issue? I hope it's not as bad as power pump or steering rack. Kinda hoping the old PAS fluid is causing the pump to struggle and will be flushing it ASAP. Also does anyone know how much fluid will I need?
Sorry for really long write up, hope that makes sense and someone will be able to help me crack that mystery.
Thanks!

[TLK]

F10s have some kind of "eco" pump that is overly complicated and produces strange noises when starting out for the day. So there's more with this pump to go wrong than a regular pump.

In general for any pump loud noises and increase in steering effort is often air in the system or loss of fluid (seems like you aren't losing fluid) or more rarely dirt. Try parking and turning the wheel fully lock to lock at least three times and see if there is any difference. Also inspect carefully with a good light and maybe take off bottom cover to see if fluid is leaking but just not dripping on the garage floor.

With this pump though what you are experiencing is probably pump failure.

[Luk4shO]

Originally Posted by TLK

F10s have some kind of "eco" pump that is overly complicated and produces strange noises when starting out for the day. So there's more with this pump to go wrong than a regular pump.

In general for any pump loud noises and increase in steering effort is often air in the system or loss of fluid (seems like you aren't losing fluid) or more rarely dirt. Try parking and turning the wheel fully lock to lock at least three times and see if there is any difference. Also inspect carefully with a good light and maybe take off bottom cover to see if fluid is leaking but just not dripping on the garage floor.

With this pump though what you are experiencing is probably pump failure.

Ever since I topped up the fluid back to the correct level the pump never made a slightest of sounds. Also I did turn the wheels lock to lock about hundreds of times, still the same. Fluid is not frothy, milky and has no bubbles in it.
It is also controling in all the modes, it just it feels like Comfort is now Sport and Sport+ is Sport++.
Is it possible it's something as silly as fluid gone bad or strainer inside the reservour is blinding?

[Craze]

Are u certain u arent imagining it? No offense

[Luk4shO]

Originally Posted by Craze

Are u certain u arent imagining it? No offense

None taken Initially that's what I though but after having light steering for first half a minute or so after starting the car and my recent trip around town when it was so bad that I didn't enjoy the car at all. It was so inconsistent, like half way throught the turn I did have a proper power assistance and then all of a sudden it would go heavy. So no, I'm sure it's not in my head

[M5Rick]

An '11,that'll be one of the first batch of the ones produced.As TLK stated its not a straight forward pump and I hope that driving it while low didn't add to any of its woes.
I'd drive it straight to Bm if it was mine.

[technician117]

I would start with a better/full fluid flush with CHF 11S but it sounds like the pump is giving out. Also remove the lower skid panel to look for leaks. There is a lot of surface area to get coated in leaking fluids before they make it to the ground.

[TLK]

I looked this up in TIS and the whole system is complicated. There is a servotronic valve on the rack itself to adjust the amount of assist, and there is an ECO valve on the pump to also adjust the pressure.

The system relies on a few inputs, including wheel speed, and supposedly in the case of M cars, the servotronic control current is generated by the DME and not the ICM like all other non-M models. So besides the purely mechanical faults we've talked about already, there could also be wiring, connector, control module, or valve problems.

You could try reading out the error codes using ISTA+ if you have that to check if any faults are stored related to the power steering, but otherwise it looks like professional help is needed.

[Luk4shO]

The car is going to BMW for a service on monday so I'll get them to check the whole system. I'll update this thread with any findings

[Craze]

Please do let us know