Power Steering Fluid - CHF11S to ATF

[prostcfc]

I'm going to switch to ATF. It is said not to mix, but I found this nugget (https://www.bimmerfest.com/threads/w...3868/?u=268063) which includes a service bulletin stating:

"CHF and ATF oils must not be mixed. The oil types are indeed compatible, but if there is more of the one type in the steering gear then the other, this adversely affects the properties of the other oil."

So if there is a little CHF stuck in the steering rack (I've read it can be a bit difficult to get everything out), seems like that isn't the end of the world.

[bigjae46]

Do you have to blow out the PS lines and rack when switching from CHF11 to ATF and vice versa? I'm thinking about changing my E90M3 to ATF.

[Slideways]

Do you have to blow out the PS lines and rack when switching from CHF11 to ATF and vice versa? I'm thinking about changing my E90M3 to ATF.

Depending on how much ATF you have on hand, my guess would be to drain the CHF, fill with ATF, run the engine for a few minutes, drain the ATF, refill, drive for a few 100 miles, drain and refill again. Castrol Dextron IV is ~$45 for a pack of six.

[bigjae46]

Depending on how much ATF you have on hand, my guess would be to drain the CHF, fill with ATF, run the engine for a few minutes, drain the ATF, refill, drive for a few 100 miles, drain and refill again. Castrol Dextron IV is ~$45 for a pack of six.

So not an instantly deadly sin to mix a little but do want to flush and couple of times. I can do that…I think

[Slideways]

So not an instantly deadly sin to mix a little but do want to flush and couple of times. I can do that…I think

I mean, if you want to get really crazy, it is probably a good time to change out the reservoir on the final refill since the reservoir has a filter in it.

I have a feeling most track guys would just dump the CHF, refill with ATF and call it a day

[BTB]

I don't know what the reason was, but the e9X M's suffer from power steering feeling boiling on track even in noob group.

Can confirm … on a wet October day in Wisconsin (Road America)

[bullet0770]

I am installing a new rack as the old one started leaking from boot seal. I changed the steering fluid to CHF11S but the steering leaked a year back and I was topping it with CHF 11S, not sure CHF was the reason (Flushed the system when moved to CHF11S in 2013). The hoses are fine and were not leaking. Now what should I replace? Those hoses are crazy expensive if I go to replace all? I have the car steering rack removed and planning to flush the hoses with ATF (filling the reservoir and running the fluid through them. Is this fine?

Thanks

[ac427]

Perhaps a synthetic and thinner ATF is available for the best of both worlds?
I.e. more feel and no boiling over on track.

[jayjaya29]

I would replace the reservoir at a minimum. Switching from CHF to ATF was a mess and even with copious flushing it seemed like the ATF was still contaminated.

[bigjae46]

I would replace the reservoir at a minimum. Switching from CHF to ATF was a mess and even with copious flushing it seemed like the ATF was still contaminated.

I would imagine you'd need to drain and blow out the rack and the pump and then lots of brake cleaner.

[bullet0770]

I would replace the reservoir at a minimum. Switching from CHF to ATF was a mess and even with copious flushing it seemed like the ATF was still contaminated.

I would imagine you'd need to drain and blow out the rack and the pump and then lots of brake cleaner.

I have the reservoir but it looked fine and did not want to break the hose while removing it. I will give it a try. Steering rack is new and no fluid in it. After so many years the red ATF was still dripping yesterday even after flush with 2 litres.

[jayjaya29]

I'm confused, how is the fluid in your system still red? Clean CHF-11S is green.

[bullet0770]

I'm confused, how is the fluid in your system still red? Clean CHF-11S is green.

I see traces of red, the fluid itself is whitish green.

[jayjaya29]

So its a mix of both still. Personally I'd stay with ATF since it doesn't leave a horrible mess when it leaks. If none of your hoses were leaking I wouldn't touch anything and just install the rack.

[bullet0770]

So its a mix of both still. Personally I'd stay with ATF since it doesn't leave a horrible mess when it leaks. If none of your hoses were leaking I wouldn't touch anything and just install the rack.

Thanks for your reply, reason I am not trying to even change the reservoir even though I bought the replacement unit.

So fill the reservoir with mobil 1 ATF and drain it to cleanse the hoses. then just replace the rack. and fill with ATF. does this sounds good?