E39 540 - confirm orientation of PS hoses at cooler

[BostonJon]

Hi, Everyone-

I'm slowing tracking down the source of several power steering leaks. I had a leak at the bottom of the reservoir and replaced the reservoir along with the return hose (reservoir bottom to cooler) and this has fixed one leak. The other hose at the cooler (to the rack) is also leaking where the soft rubber part meets the metal flange (near the cooler).

Here's my question:

The cooler inlet has two holes - one for the hose going to the reservoir and one for the hose going to the rack. On mine, the return line that goes back to the reservoir is on the BOTTOM INLET to the cooler and the hose to the rack (with the locking tab) is on the TOP INLET to the cooler. Interestingly, realoem (link below) shows them oriented the other way (reservoir hose on the top, rack hose with the locking tab on bottom). Which way is correct and does it even matter?

Edit: after thinking about this some more and reading some other posts, it looks like others have commented about the realoem diagram for these hoses being inaccurate. Either way, the only thing that would change is the direction of the flow of fluid though the cooler. And unless there is some one-way check valve in there, I don’t think it would matter which way the fluid flowed.

https://www.realoem.com/bmw/enUS/sho...27#32411094205

[Iamthebull]

My be 540i is having power steering leaks as well, but I'm just replacing every hose, the reservoir, everything except the pump. FCP has a kit that I'm going to pick up for peace of mind.

[MotorMouth93]

I've had my PS hoses hooked up backwards to the cooler for a few years now. Doesn't seem to cause any issues so I'll just fix it next time I flush the fluid.

[BostonJon]

But which orientation is the correct one?

[ross1]

Reservoir hose goes on top.
WRONG see post 21

[BostonJon]

Thanks. How were you able to confirm this?

[ross1]

Because there are very few parts of this car I'm not familiar with and just installed the drivetrain into one this past weekend. Good enough?
The real oem diagrams are often useful but not an assembly manual.
As stated before the cooler couldn't care less which direction the oil flows.
well this is embarrassing See post 21

[BostonJon]

Because there are very few parts of this car I'm not familiar with and just installed the drivetrain into one this past weekend. Good enough?
The real oem diagrams are often useful but not an assembly manual.
As stated before the cooler couldn't care less which direction the oil flows.

Thanks. I wasn’t challenging you, just trying to understand how/where you were able to confirm the orientation given the discrepancy between real OEM and what appears to be the actual orientation of the lines. I don’t see why the flow direction would matter and I don’t have any issues with the steering now other than the leaks, which seem to be pretty common.

[ross1]

The way these are put together that clamp swings to the outside. If putting them on without the radiator in place the tendency might be to reverse that(which results in switching positions)as there is more room to work on the inboard side without the radiator in place.
Don't forget to replace the 0-rings too PN 17 21 1 742 636

[BostonJon]

great point about the orientation of the clamp. Looking at the RealOEM diagram, the clamp is on the bottom hose and would need to swing inward (towards the radiator) - counterclockwise when looking from the front of the vehicle. as ross1 noted, this would potentially cause some space issues because of the radiator.

however, if the clamp were on the bottom hose (as it seems to be in our cars), it would swing counterclockwise but away from the radiator and there would be plenty of room to work on the hoses.

[Auto Parts Guy]

Both my 540i and M5 have the reservoir hose on bottom. For whatever that's worth. Owned the M5 for 5 or 6 years and no issues, although I did replace the reservoir and hoses at some point if I remember correctly.

I haven't driven the 540i long enough to have any history but no steering issues that I know of.

First pic is the 2001 540i 6 speed, second 2 pics are the 2000 M5. Hope it helps. Hard to get good pics with the second air box in the way.

IMG_20230111_190842720.jpg

IMG_20230111_191119273.jpg

IMG_20230111_191053569.jpg

[Auto Parts Guy]

Bentley manual pic pic shows the reservoir hose on top.
Nothing else very helpful in the Bentley that I could find.

I'm pretty sure the pictures on realoem and Bentley are inaccurate for hose to cooler orientation. There are even differences between the two.

Reservoir hose on bottom final answer ��

IMG_20230111_192318245.jpg

[Chedley]

Hi, Everyone-

I'm slowing tracking down the source of several power steering leaks. I had a leak at the bottom of the reservoir and replaced the reservoir along with the return hose (reservoir bottom to cooler) and this has fixed one leak. The other hose at the cooler (to the rack) is also leaking where the soft rubber part meets the metal flange (near the cooler).
....
https://www.realoem.com/bmw/enUS/sho...27#32411094205

To fix the leak, try to remove and replace the O-rings at the end of the hoses where they meet the flange, #11 in the diagram. There is also another hidden O-ring behind bolt #13 in the diagram.
Replacing those O-rings fixed my leak. Replacing the hoses did not.

[StephenVA]

The incorrect view of these hoses on REALOEM is a well know error. As Ross1 posted the correct orientation is Res to the top. Always replace the little O-rings! I will be doing this on my own M5 next week.

Image of 6 banger hoses are the same. Big stem on TOP, little stem on bottom.

[StephenVA]

Clean those engine bays!

[ross1]

The incorrect view of these hoses on REALOEM is a well know error. As Ross1 posted the correct orientation is Res to the top. Always replace the little O-rings! I will be doing this on my own M5 next week.

Image of 6 banger hoses are the same. Big stem on TOP, little stem on bottom.

Also, no O-ring needed for the clamp's bolt, it doesn't see any fluids.
I can't believe the number of posts for this question.

[Auto Parts Guy]

Reservoir hose goes on top.

The incorrect view of these hoses on REALOEM is a well know error. As Ross1 posted the correct orientation is Res to the top. Always replace the little O-rings! I will be doing this on my own M5 next week.

Image of 6 banger hoses are the same. Big stem on TOP, little stem on bottom.

??? Realoem and Bentley show reservoir hose on top. But if it's wrong, then how does it go on ..top??

The little stem on my cars IS the reservoir hose. Which is on bottom..

[StephenVA]

I stand corrected, realoem for M5 shows the correct orientation
years ago it showed the m5 ass backwards hence all the fights on the m5 forum over the issue

[Auto Parts Guy]

I looked at another random 2002 540i today and the reservoir hose was on bottom. Interesting nonetheless

[scubajim20]

What PS fluid did you use?

[ross1]

??? Realoem and Bentley show reservoir hose on top. But if it's wrong, then how does it go on ..top??

The little stem on my cars IS the reservoir hose. Which is on bottom..

Edit and apology to the misinformation I've been offering:
I'll have a slice of humble pie to go with that crow, please.
SO! Mr. Cocksure of himself had a look at his car today. Reservoir hose is on the bottom alright.
Not sure what I was envisioning but I'd have bet(and lost) the farm on the image in my mind of the reservoir hose closer to the observer. Perhaps because I usually am doing these from underneath after a big engine out job. Sorry, I'm making excuses.
Anyone that has reversed their set up on my account in the interest of being factory correct may feel free to administer a kick in my nads.
Please disregard all of my oh so sure of myself insistence that the reservoir hose is on top, it is not.

Functionally it doesn't matter, the oil cooler works the same regardless of flow direction.
That is all