CHF11s - I hate it so much!

Status
Not open for further replies.
M

mattsimis

Joined
Oct 9, 2009
Messages
11
Location
Ireland
Car: 1993 BMW 850CSi V12 with AHK Rear Steering running off shared power steering fluid system (CHF11s)
Problem - Tiny but consistent CHF11s weepage on metal fittings on rear pressure piping for AHK. Changed some pipes already, but "unchangable" parts already had rust damage. CHF is just too [censored] thin. Causes ABS and ASC failure (as it affects ABS modulation) too.
Amount lost - About 500ml per 3wks (which is half a tin). Low fluid levels likely bad for PS Pump(s) and AHK Accumulator and Pressure system.

Ive read all the threads here about alternatives. Ive read the seemingly "no issues" reports from Audi drivers switching to ATF (Redline and Mobil 1). However Ive read first hand reports of written off 7 series and other BMWs on Bimmerforums from using the very same switch.

I would love to ditch 11s and put in something thicker. Im going to try the very marginally thicker and newer CHF202 again, see if its any better this time round (last time a major leak vented it on the motorway). Anyone got any comments to add?
 
Last edited:
Talking about pin hole leaks here, so small I cant actually see anything more than a drop after a long drive (or where precisely its coming from). But it all adds up...
Other than thicker fluid, any magic fixes I may be unaware of?
 
Last edited:
If you can find it over there, try some Lucas Power Steering stop leak, that stuff is supposed to actually work from what I've read. It succeeded in giving the steering in my cav a bit more weight back to where I like it. I'd give it a shot.
 
I can't help you with your problem but I would like to say that you are driving my dream car and we do need pictures of it immediately.
 
I can't believe some hydraulic hose maker hasn't figured out a workaround for this. Where there's a market...
 
Originally Posted By: rudolphna
If you can find it over there, try some Lucas Power Steering stop leak, that stuff is supposed to actually work from what I've read.

I have the "Slick50" version, but it (and I think the Lucas branded bottle) are for actual Power Steering Fluid, not CHF used in a Power Steering System according to the label and the emails I had with them! So I didnt put it in.
Originally Posted By: Audi Junkie
ATF+4

Did you see the bit about guys saying their same era 7 series (and other BMWs) were virtually destroyed (not 3rd hand hearsay, their own cars) thanks to ATF or am I missing something here?
Originally Posted By: L_Sludger
I can't help you with your problem but I would like to say that you are driving my dream car and we do need pictures of it immediately.

As requested, some recent photos after I was playing with Wheel Spacers :)
http://s55.photobucket.com/albums/g136/m...ers%2016-05-10/
 
Last edited:
Originally Posted By: mattsimis

Originally Posted By: Audi Junkie
ATF+4

Did you see the bit about guys saying their same era 7 series (and other BMWs) were virtually destroyed (not 3rd hand hearsay, their own cars) thanks to ATF or am I missing something here?


No, I only see success stories on ATF+4 or I would not recommend it. I still get emails from guys telling me it works great and thanking me for suggesting it. I thought you were complaining that CHF is too thin and were looking for an alternative.

As for the destruction of entire cars from "ATF", no I havn't seen that. I suspect problems were brewing before introduction of whatever "ATF" you are talking about. Low levels, leaks, running dry, contamination...? afaik, thicker ATF+4 with it's substantial additive pack can only improve the hydrolic system performance.


Let us know what happens going forward.
 
Originally Posted By: mattsimis
... weepage on metal fittings on rear pressure piping for AHK. Changed some pipes already, but "unchangable" parts already had rust damage...

I still don't really understand where the leak is coming from. If it's confined within the hydraulic hoses, there are many shops that can custom-rebuild your hoses for you.
 
I think some components were rusted solid on the undercarriage, likely perforated too, which means contamination.
 
Leakage at fittings is not going to be cured by a thicker fluid.
Maybe it will be slightly attenuated, but the problem is faulty hardware.
 
Originally Posted By: mattsimis

Originally Posted By: L_Sludger
I can't help you with your problem but I would like to say that you are driving my dream car and we do need pictures of it immediately.

As requested, some recent photos after I was playing with Wheel Spacers :)
http://s55.photobucket.com/albums/g136/m...ers%2016-05-10/


What a perfectly-designed vehicle. How beautifully sculpted.. You get two thumbs way up!
 
Originally Posted By: mechtech2
Leakage at fittings is not going to be cured by a thicker fluid.
Maybe it will be slightly attenuated, but the problem is faulty hardware.

An improvement would be fine. Bear in mind we are talking about a myriad of metal pipes going from the front to the rear of the car, then back again.
Originally Posted By: Kestas

I still don't really understand where the leak is coming from. If it's confined within the hydraulic hoses, there are many shops that can custom-rebuild your hoses for you.

Its not the hoses, but the metal pipes its the large female threaded fitting that mates to the smaller male one. The I replaced the rusted through section from the rear AHK pump to the line that goes to the front, but that required using a hack saw to get the two theaded bits apart (the original male piece remains on the remaining metal pipe) which damaged the threads somewhat. That is likely the only major leakage point.

Photos of the old part (the rusted one wasnt painted, now replaced):
http://s55.photobucket.com/albums/g136/mattsimis/850CSI/Parts/Rusted Parts/
Originally Posted By: Audi Junkie

No, I only see success stories on ATF+4 or I would not recommend it. I still get emails from guys telling me it works great and thanking me for suggesting it. I thought you were complaining that CHF is too thin and were looking for an alternative.

As for the destruction of entire cars from "ATF", no I havn't seen that. I suspect problems were brewing before introduction of whatever "ATF" you are talking about. Low levels, leaks, running dry, contamination...? afaik, thicker ATF+4 with it's substantial additive pack can only improve the hydrolic system performance.

I may not post here much, but Ive read your posts many times. I agree with your approach that sticking to "whats in the book" and outright ignoring decades of Oil improvements is a backwards, head in the sand approach. I want you to be right!
However, at Bimmerforums, unlike the Audi forums where there was an absence of actual 1st hand info, there are a handful of BMW guys that claim serious damage to their own pristine cars from ATF usage in CHF systems. Specifically a rather immediate and disasterous reaction to cars with rear self levling. I dont have Self Leveling, but I have rear steering and no specifics on just how it affected the Self Leveling systems so badly.. There were some claims that ATF is "25% detergent", destroys seals (and evidence with the self leveling suspension) and most wont even use non-Pentosin branded CHF.
http://forums.bimmerforums.com/forum/showthread.php?t=1364910&highlight=pentosin+atf
This is quoted frequently:
"Pentosin is a large temperature range (Multi-viscosity like) Hydraulic system fluid.Pentosin 7 is a mineral based oil and Pentosin 11 is a full synthetic. ATF is basically a high detergent 20w oil with the lubricating property additives modified to make it Dexron or Mercon. The additives and detergent levels in ATF make it very "Poisonous" to a Pentosin based system. Seal leakage is the result of mixing them."
 
Last edited:
Any idea what Euro makes speced before CHF? Dexron. When VW did the changeover to CHF c.1992, the PS part numbers stayed the same. Same part, different fluid, hints at compatibility. Hoards of Audi drivers have used M1 ATF for years with nothing but improvement in their systems.

ATF is LOW detergency, because AT is a sealed system, w/o combustion or outside comtamination.

It's pretty obvious from my experience, the BMW systems in question were in failure mode before the red fluid was added. Just like when VW techs blame the customer for topping off their failing cooling systems with Dexcool, which is 100% compatible, if not identical to the VW G-12 fluid. It's a chicken-and-egg question that has the answer of, why did the owner need to add fluid?

I'm not involving myself in a technical debate with people outside the forum. If they want to come here and test their theories about "incompatibility" and "25% detergent", their arguments will rise or fall of their own merits.

Bottom line in my analysis of PS systems is the CHF is too thin, and way too thin when heated. The heating and thinning allows the pump to have metal-to-metal contact, producing more runaway heating and shedding metal into the system (which has been removed by the Dixie cup fulls by Audi forum members). The metal abrades the seals and the heat warps them. You have to decide for yourself how/if this relates to your own system. Do some back reading here, ATF+4 is very popular as an ATF, withgreat specs and additives, and it is approved as well as used by Mercedes Benz, who likely uses the same parts supplier as BMW.
 
Maybe the idea the ATF is detergent goes back to the "ATF as an engine cleaner" myth.

When this forum debates and debunks myths that were addressed 8 years ago, it kind of takes a big step backwards. However, I'm putting in the effort because you seem earnest about getting beyond the myth-repetition cycle that is pervasive on the internet.

A lot of Audi guys add CHF by the gallon till their systems fail, but they stand by the product. I ask them, if CHF is so great, why did your PS pump and rack fail at 55k?
 
Well my approach to things isnt popular everywhere, I like to try make things better than tow the safe line.
What Redline product would you recommend then, their Fully Synth "Power Steering Fluid" or their D4 ATF product?
 
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.

I am very surprised to hear that CHF11s, a fully synthetic hydraulic oil, and ATF shared a part number. Are you sure it wasn't CHF7.2, a mineral oil based product?
 
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?
 
Status
Not open for further replies.

Similar threads

G-MAN
  • Locked
New 600bhp Continental GT Speed
Replies
11
Views
4K
G-MAN
Back
Top