Viscous Fan storage


New member
I need to replace my viscous fan. I notice in most posts on the subject the we are told to store it vertically, otherwise it will fail. Is this advice from Mercedes?

The thing is, are they always kept vertically in the container they arrive in from China / Taiwan / Germany? Ditto in the delivery truck to the warehouse? On the warehouse shelf? On the parts stockists shelf? In the factor's delivery drivers van? Are they really that sensitive to orientation, because if they are they wouldn't survive a rough sea voyage or take off and landing in a aircraft, or hard breaking when installed for that matter.

Or is it ok to store it horizontally, as long as it is then stored vertically for a period of time before fitting?

Bearing in mind that it whirls round at up to 3500rpm when fitted, the dominant force is centrifugal (centripetal if you're being picky) rather than graviational.

I'm not seeking to criticise anyone's prior post here, just seeking informed advice before I buy one online (considering how most couriers treat parcels) or order one from a factor (having seen the way their delivery vans are driven).


Aqua Puttana

Poly - Thread Finder
My theory is that in the new units the fluid is contained within the proper area. Once it is installed and spun up with the thermal unit activated then the fluid distributes. Once the fluid is out into the unit if it not properly stored vertically then the fluid may migrate to the wrong places and not return to "normal" even when spun up and heated.

The common advice for all vehicles, not just Sprinters, is to keep removed centrifugal fan units vertical. You may get away with storing it horizontally and then returning it to vertical. I choose not to test that.

Good luck. vic
Last edited:


Erratic Member
I need to replace my viscous fan. I notice in most posts on the subject the we are told to store it vertically, otherwise it will fail. Is this advice from Mercedes?
From the service manual:


(bold printing: theirs, red highlighting: mine)

No, they didn't bother to go into a long-winded technical explanation of "why not" and "what happens if" (i wish they had).

p.s. i fully agree with your concerns about "what happened to the new part during storage/shipping?"

Old Crows

Calypso 2014 View Profile
The school solution is vertical storage.....


New member
So the upshot of this is NEVER buy a used viscous fan since it will certainly have been horizontal, and flung about randomly, in the back of the courier van by the time it gets to you.

I do wonder why they fit them at all since i) They don't seem very reliable, judging by the vast numbers of posts about them, whereas a simple thermo switch & electric fan very rarely fails. ii) It puts aditional load on the water pump bearing which already has a hard life. iii) It's directly driven so increases fuel consumption. Only fractionally I know but in the fleet supply war a fraction of an mpg/lp100k is a significant cost for a large fleet.



New member
They are normally fitted in the box at a 45 deg. angle, that way it will always be vertical or at a 45 deg angle, Unless you store your square box at an 45 deg angle.
I have installed used clutches but have always put them vertical for a while before using, have never had any failures.

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