CHF11s - I hate it so much!

[JHZR2]

Suprisingly the chf11 system in my Saab and my fathers MB have not failed at 50 and 220k respectively.

IMO there is something else wrong here, and IMO the OP needs to get back to square one wrt the tightness of his system first and foremost. No hacksaw job can be excused from being viewed as the likely culprit. Fix that first on both sides.

AJs theory on fluid overheating and allowing metal wear is plausible - however a small cooler would fix this. I've heard of issues with comparability being an issue, so while the parts may be the same, there may be basestock or additive clash issues with the fluids, making mixing or swapping without extremely good flushing a possible issue. We do not know what happens when the mixed fluids encounter the physics of the system.

I'd get to the bottom of the system issues first, then we can start to discuss fluids. Once the system is proper and right, then we can possibly open it up and apply different fluids. Until then, it is premature.

 

[Audi Junkie]

Originally Posted By: MI_Roger

I am very surprised to hear that CHF11s, a fully synthetic hydraulic oil, and ATF shared a part number.


I said the PS *PARTS* on the car stayed the same.

 

[mattsimis]

Originally Posted By: Kestas
I looked through the pictures. You say the horribly rusted pipe section was replaced. I still don't understand the whole picture, where it's leaking, and why this can't be mechanically fixed. Can you perhaps put teflon tape around the threads where it's leaking?


Yeah, I did do that. Visualise the following:

Metal pipe near wheel arch (rear) coming down towards ground
Floating male threaded piece, cannot be removed as the end of the metal is flared (ie to give it clamping pressure when tightened)
Female, solid threaded pipe, new, attaches to male thread.
Male thread piece badly rusted, slight drips from this area.

To replace the male threaded piece a small section of the metal pipe would have to be cut off to slide it out, then a new threaded piece installed, then the end of the pipe flared again. All would have to be done in-situ, with about 8cm of "play" and some chance of further damage to fragile, rigid pipes if care not taken. I think it would be better if I did that myself than take it somewhere, but Id need some more tools.

Originally Posted By: MI_Roger
I assume you know that CHF11s has been replaced by CHF202? My local import auto parts store now sells both, but I expect the CHF11s to eventually disappear.

In my OP I mentioned I tried it, unfortunately the old (now replaced) very badly rusted pipe sprayed it all out and its a nightmare to source here. I had to get the unbranded GM version from a Range Rover dealer, it didnt say what grade CHF it was, but the application list implied that car (a certain year Freelander) was CHF202 only.

 

[gamefoo21]

To the OP,

I've used Redline PSF as a solid replacement for a VW which specs the CHF11s.

The CHF11S when I drained it was black.

I would reccomend using either the Redline PSF or C+(Redlines +4 ATF) or a good quality +4 fluid.

 

[mattsimis]

Originally Posted By: gamefoo21
To the OP,

I've used Redline PSF as a solid replacement for a VW which specs the CHF11s.

The CHF11S when I drained it was black.

I would reccomend using either the Redline PSF or C+(Redlines +4 ATF) or a good quality +4 fluid.

Interesting, FWIW, I got this reply from Redline:
"Thank you for contacting Red Line Oil, if your 850SCi has hydroboost requiring the CHF11S, a special low viscosity fluid, we don’t offer a cross. Some have used the PowerSteering Fluid to replace the CHF11S fluid with good results though these are different fluids and at this time don’t have a recommended replacement for it. "

 

[gamefoo21]

Bah...

-56c pourpoint vs -50c on the Redline.

Which would you rather have, something that can be poured in temps so low you'd have to keep a gas engine running or something that can handle going above 100c without boiling?

The only reason Redline can't cross is because of the rediculous low temp capability of CHF11s... 202 is -52c and can barely handle any higher temps than 11S.

The steering is much improved with Redline, the steering wheel responds without much of a deadzone at center, rather than with the 11s which had a nice few degrees before the wheels would move, used to wiggle the steering wheel and the car would keep going straight... :lol:

As far as I can tell, MB does use the same steering components as VW, and MB specs +4 ATF, which is a direct cross for the Redline PSF.

Edit: The 11S after a drive was so thin that if you held the dip stick vertical it would run off the stick and leave it looking dry. I choose a slight amount of drag on the system at -40c rather than having the fluid fail to function on a hot summer day of +40c and some spirited driving.

 

[mattsimis]

Originally Posted By: gamefoo21


As far as I can tell, MB does use the same steering components as VW, and MB specs +4 ATF, which is a direct cross for the Redline PSF.


Yeah, the issue here is BMW on the other hand dont seem to use the same parts and there seems to be specific and repeated failures with various BMW parts when not using CHF.

 

[gamefoo21]

If BMW is using it as a shared hydraulic system, I'd look closer at 202 since it's supposed to be a direct replacement for 11S.

11S has crazy low temp abilities, but 202 isn't really all that in any department.

As well, it seems that the CHF type fluids react badly when you use other fluids with them. If you could do a full flush of the system, you might be able to get away with using something else, but you'd have to flush out all the old stuff.

 

[mattsimis]

Yeah, Im looking out for CHF202, very hard to find though.

 

[bmwtechguy]

My experience with CHF 11s is that the only advantage it offers is great low temp operation as it is very thin. I have seen just with my eyes a lot more tiny metal flakes floating around in the fluid with CHF 11S than with ANY other ATF or power steering fluid. I would seriously consider the ATF+4 as it works fine. M1, Redline, Amsoil, ATF or power steering fluid are all options, but the ATf+4 will get the job done for less $. The only vehicles that I have not tried a non-CHF 11S in is those cars with ARS, active-roll stabilizaton. The system is closely tuned to the viscosity of the CHF fluid and may throw pressure errors if another fluid is used.

 

[Audi Junkie]

Originally Posted By: mattsimis
Originally Posted By: gamefoo21


As far as I can tell, MB does use the same steering components as VW, and MB specs +4 ATF, which is a direct cross for the Redline PSF.


Yeah, the issue here is BMW on the other hand dont seem to use the same parts and there seems to be specific and repeated failures with various BMW parts when not using CHF.


I thought we covered this.

Do you claim the systems never fail on CHF 11S?

That's what it would take to make your statement valid.

 

[mattsimis]

Well come on now, nothing on a any car could be said to never fail, so your question is unanswerable and your proof completely unattainable.

The CHF11s cars do of course have generic issues, like small leaks after 10years and such. They dont however has rapid failure like the rear suspension does when ATF was put it on certain BMWs. Thats as close to a testament you an get, there is precedent for extremely bad outcomes on BMWs with the proposed switch, its not realistic to quote Audi, VW and Merc, they are simply different cars.

I accept people were putting it in "for a reason" and you could extrapolate that maybe they were going to fail anyway, however in some cases I looked up, the ATF was either put in intentionally as a replacement or as a top up on CHF when some power steering hoses etc upgraded. The AHK system is so rare and specialized, with vastly more "plumbing" than a regular cars system, there is nothing comparable on the relatively "regular" cars Ive seen the ATF switch done on.

I really want to believe I could put in ATF, but Ive seen not comparable reference car and while Im usually on for trying "anything" the AHK parts in an 850CSi cost approx $15,000 from BMW (yes the parts, not the car).. if it were to go badly I would be left with nothing but a crippled car and a failed theory from an internet forum.


Originally Posted By: bmwtechguy
My experience with CHF 11s is that the only advantage it offers is great low temp operation as it is very thin.
-snip-
The only vehicles that I have not tried a non-CHF 11S in is those cars with ARS, active-roll stabilizaton. The system is closely tuned to the viscosity of the CHF fluid and may throw pressure errors if another fluid is used.


Two questions:

- The fact its very "thin" means that its going to flow different to ATF. Why is it assumed this isnt an issue in an 850CSi, which runs Power Steering, Rear Wheel Steering and Brake Boost from the PSF? Surely the "thinness" is a designed part of the system.
- You note you havent tried it in cars with ARS.. a curious statement, why did you simply "not" try it? The AHK system has its own pressure acculumlator and electronic monitoring system and its piped from front to rear. Surely that is a system "finely tuned" to the specifics of 11s? Granted it may be a [censored] fluid, prone to shearing (though the 850CSi has a PSF cooler), but that does not make ATF a drop in replacement if everything else in the car is setup for a very specific and limited range of fluids.

 

[gamefoo21]

If the Pentosin site was up and running, I'd pull the specs, and we'd see that if in the regular operating range what the various viscosities are.

If I remember right from when I was trying to figure this out for the PS system, the Redline PSF was veeeeery close to CHF202 across the spectrum as far as viscosity of the fluid was concerned.

In something like this I would reccomend sticking to a PSF rather than an ATF, since Redline PSF is a single weight synthetic rather than an atf which does use viscosity improvers.