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      07-19-2018, 03:51 PM   #1
Rombbb
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Your choice of three steering fluid flush methods ?

Am planning on doing as complete a flush as possible and the online sources eaxch seem to have their own pro's and cons :

---> Turkey bastering, filling up, engine start, turning wheel end-to-end, redo until clear fluid

Will be quite hard to recognize 'clear' from a black reservoir and guess will always keep old stuff in

---> Disconnecting oil line from rack cilinder, turning the wheel

I guess without the pump running you won't get all fluid from around pump area, with the stationary blades acting as a seal, although the rack is the lowest point of the system so maybe it does work if fluid can drain past the pump

---> Disconnecting return hose from reservoir, letting engine run with steering wheel straight, adding to reservoir until clear fluid exits hose

I guess this way you don't get all old fluid from PAS cilinder with steering wheel straight only (will remain old fluid left and right from the valve in the rack cilinder)

Probably the best is doing a combination of them, but that in itself has cons.

What's your way ?
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      07-19-2018, 05:51 PM   #2
XMetal
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I use the Turkey Baster method with Mobil 1 synthetic transmission fluid. I have been doing this annually with my oil change on the X5 in the past 14 years - no power steering issue to date and the fluid is clear cherry red each year that I pull it out of the reservoir. Although, I have been slacking a bit on the Z and only does it every 2 or 3 years since the reservoir is so darn difficult to get to.

I use a clear jar to temporarily hold the old fluid that was "sucked" out of the reservoir so I can visually inspect it's "cleanliness".
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      07-19-2018, 06:14 PM   #3
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I used a power bleeder to ensure everything was flushed out. Bit of extra effort but it worked well enough.

https://www.zpost.com/forums/showthread.php?t=1459366



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      07-20-2018, 05:17 AM   #4
Rombbb
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Quote:
Originally Posted by XMetal View Post
I use the Turkey Baster method with Mobil 1 synthetic transmission fluid. I have been doing this annually with my oil change on the X5 in the past 14 years - no power steering issue to date and the fluid is clear cherry red each year that I pull it out of the reservoir. Although, I have been slacking a bit on the Z and only does it every 2 or 3 years since the reservoir is so darn difficult to get to.

I use a clear jar to temporarily hold the old fluid that was "sucked" out of the reservoir so I can visually inspect it's "cleanliness".
Thanks, that's the way I wanna go, but problem is that I have no guarantee when it was done the last time, if ever.

I still have to check schematics of the system but I guess for a full flush the best is to disconnect the return line from the reservoir, lift front and turn the wheel left and right. Hopefully by keeping the reservoir topped up, through suction and pushing power of the valve in the rack cilinder this will move all old fluid out. Then start the engine to spin the fluid pump and keep wheel straight to pump the old fluid from the 'cilinder not engaged' part of the circuit piping. Then all should be out.

Problem is that trial and error in this regard is expensive, 30 euros per litre here

But I guess it's worth it because turkey bastering, while good when regularly done, maybe won't do for a full flush.
Assuming the reservoir contains approx 50% of total circuit oil; after renewing it and running the engine, steering left and right, old and new will be mixed, let's say pretty evenly. Then when you re-renew the reservoir only 50% of 50% = 25% will be further renewed. Let's say afterwards old and new again gets mixed up evenly, the 3rd run will clean out 50% of 25% = 12,5%, then 50% of 12,5% = 6,25% etc.
So it would require at least three runs, which if course is perfectly doable, but this is all assuming that old and new mixes evenly by running the pump and steering. I can imagine this not to be the case and that old and new remains concentrated in different sections of piping (although 'steering' old and new from thinner piping into bigger rack cilinder and the bigger reservoir itself should mix it up I guess).
If it doesn't mix up perfectly you either need to know where the old is to get it to stop in the reservoir tank which isn't really possible. Or just go more at random, say stop after 5 or 10 full steering locks, but then there's no guarantee that certain sections of piping do not still contain concentrated levels of old fluid.

TL;DR am pretty OCD :-)

Turkey bastering seems pretty fine thinking about it, especially done with not too long intervals, but just for that extra peace of mind, giving that I don't know when it was last done, this time I'm going for the hose method.

But thinking about that I'm now doubting whether it would work; disconnecting the return hose, turning wheel left and right, the amount of fluid in the cilinder will be pushed out the hose but without the pump running I doubt whether the cilinder gets refilled with new oil for the next turning cycle. Gravity alone may be not be quick enough to fill the cilinder in the timeframe the left or right circuit is opened (due to torsion beam fluid jacks being lined up in the PAS mechanism during steering time). So at one point you could run dry with still old fluid in the system. Hopefully the steering straight with pump running phase takes care of that.

Man, this is soooo tiring. Wy doesn't BMW simply design and give a simple and bulletproof way to completely drain systems. Same goes for coolant. There is no such thing as life time fluids...

Last edited by Rombbb; 07-20-2018 at 06:51 AM..
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      07-20-2018, 05:22 AM   #5
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Quote:
Originally Posted by steffenme1 View Post
I used a power bleeder to ensure everything was flushed out. Bit of extra effort but it worked well enough.

https://www.zpost.com/forums/showthread.php?t=1459366

Wow, that's an idea I didn't think of yet !

EDIT: just saw the link, please disregard below :-)

Was it hard finding a good fitting cap ?

What was your draining point, the return line ?
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      07-20-2018, 06:05 AM   #6
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Quote:
Originally Posted by steffenme1 View Post
I used a power bleeder to ensure everything was flushed out. Bit of extra effort but it worked well enough.

https://www.zpost.com/forums/showthread.php?t=1459366

How much pressure did you put on the system ?

Think I'm gonna go your way as well

EDIT : nevermind (again :-), just saw the other thread with answer in it
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      07-27-2018, 07:15 AM   #7
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Just open up a banjo bolt on the rack and let it drain out. I've drained my E90 3 times via one of the banjo bolts and haven't even replaced any of the crush washers. No need to be afraid of opening up the system. Not sure why some BMW owners are so OCD. It's just a car with standard parts. There's no magic in it.
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A manual transmission can be set to "comfort", "sport", and "track" modes simply by the technique and speed at which you shift it; it doesn't need "modes", modes are for manumatics that try to behave like a real 3-pedal manual transmission. If you can money-shift it, it's a manual transmission. "Yeah, but NO ONE puts an automatic trans shift knob on a manual transmission."
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