Stiff viscocoupler keeps radiator fan at full speed

Memo

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Hi,

My problem is that the radiator fan never stops spinning at full speed. It never idles. The coupler is stiff when cool. Not only can you not spin the fan, but if you force it a bit, it returns to the same position. Impossible to raise the engine temperature above a third on the gauge.

I have this setup:

As far as I and several mechanics can tell, there is nothing wrong with the installation. The water pump is correct for the coupler. As we understand it, there should be no sorcery involved, just mount it it on with the correct bolts and spacers, make sure it’s not touching anything and let it do it’s job. The coupler has maybe 500km on it. I have another, unused, which is the same. A third, used coupler from another car is only a bit less stiff. So it’s unlikely they are all malfunctioning. What are we doing wrong?
 

lip277

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Have you compared how they are before and after installation? Meaning - sitting on a table (at room temp), they spin ok but become stiff when installed //// or are stiff both not installed and installed??
 

Memo

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Have you compared how they are before and after installation? Meaning - sitting on a table (at room temp), they spin ok but become stiff when installed //// or are stiff both not installed and installed??
I have one that is installed and spins the fan hard all the time. Another, unused and uninstalled fr now, that is stiff. The old one, unistalled, stiff, but less so, presumably from use on another car.

This is what makes me think that there is a trick to the mounting.

Thx
 

tochi

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Hi,

As far as I and several mechanics can tell, there is nothing wrong with the installation. The water pump is correct for the coupler. As we understand it, there should be no sorcery involved, just mount it it on with the correct bolts and spacers, make sure it’s not touching anything and let it do it’s job. The coupler has maybe 500km on it. I have another, unused, which is the same. A third, used coupler from another car is only a bit less stiff. So it’s unlikely they are all malfunctioning. What are we doing wrong?
There may not be anything wrong with the installation. While it may seem improbable that all three examples are malfunctioning, it is not impossible.

How old are these fans, who manufactured them and how have they been stored? While reasonable minds might differ, some sources “suggest” that viscous clutches should be stored vertically or with the fill point (for silicone oil) facing up, presumably to minimize fluid leakage. https://www.mye28.com/viewtopic.php?t=72248 Setting aside age and/or poor storage/mishandling, as “unlikely” as it may seem, even brand new viscous clutches can fail. Years ago we experienced a two or three out-of-the-box failures. The parts distributor was somewhat incredulous, when seeking replacements. But after receiving similar complaints, they hypothesized that one or more batches may not have been properly filled with silicone oil. (I vaguely remember that each new part seemed to have an unusual amount of rust prevention, i.e., they seemed "oily.")

For what it is worth, there were two different style fan clutches near by. Both have been sitting idle for years - yet each spins with a small amount of resistance - versus the significant resistance you describe.

Viscous fan .jpg




In a correctly functioning system we would see that when an engine is started the fan clutch will be engaged to exactly the same extent as it was when the engine was last shut down. This means that even if the engine is ice cold when started, the fan would be fully engaged if the engine was running at full thermal load when it was last shut down. This is because the oil volume in the grooved space between the input and output sides is still the same as when the engine was shut down and the clutch stopped rotating. When the engine is first started again (when it is cold) the oil in the working chamber (the grooved space between the input and output halves) will start to circulate back to the storage reservoir thereby decreasing the drive force transmitted by the fan clutch back to the point where the fan is completely disengaged. At this point the fan will rotate with only a very small drive torque resulting from the frictional forces in the bearing. As the engine heats up, the air coming through the heat exchangers will heat up also, in response to which the thermal element on the front of the clutch will start to progressively open the valve controlling the oil flow. This will cause the drive torque of the system to progressively increase in balance with the thermal load on the system up until the point where it is fully engaged again.


A small deviation from the above pattern will be seen when a cold start up is performed due to the effect of oil viscosity which is higher at low temperatures than at operating temperature. The effect of this is that when the oil is cold the amount of fan engagement will be higher for a given amount of oil in the working chamber than when the oil is warm and a certain amount of fan engagement will therefore always be present on a cold start up but it will fall away relatively quickly as the oil heats up (due to internal friction) and the fan clutch reverts to the correct (low) level of engagement in response to the low thermal load under that condition. https://www.silverton-mahle.com/technical-information/viscous-fan-clutches/


images to ponder?

05a5a3a280ea375cd24e8aef0b6f4022.jpg


74492c9327063aba251c9f2fae43fd8c.jpg

bmw-e9-restomod-tyl-bok.jpg



Custom-BMW-E9-Engine.jpg
 

bavbob

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I recently posted a problem with this identical setup. Mine was that the fan spun freely because part #8 in the diagram which is also visible on the red fan above, was worn. The fan went along for the ride but was free to spin independent of the coupler, the coupler never engaged. Perhaps this happened previously to yours and so someone took the liberty of locking the entire setup which would explain why you cannot spin the fan by hand. You should take the setup apart to see what's what.
 

Memo

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There may not be anything wrong with the installation. While it may seem improbable that all three examples are malfunctioning, it is not impossible.

How old are these fans, who manufactured them and how have they been stored? While reasonable minds might differ, some sources “suggest” that viscous clutches should be stored vertically or with the fill point (for silicone oil) facing up, presumably to minimize fluid leakage. https://www.mye28.com/viewtopic.php?t=72248 Setting aside age and/or poor storage/mishandling, as “unlikely” as it may seem, even brand new viscous clutches can fail. Years ago we experienced a two or three out-of-the-box failures. The parts distributor was somewhat incredulous, when seeking replacements. But after receiving similar complaints, they hypothesized that one or more batches may not have been properly filled with silicone oil. (I vaguely remember that each new part seemed to have an unusual amount of rust prevention, i.e., they seemed "oily.")

For what it is worth, there were two different style fan clutches near by. Both have been sitting idle for years - yet each spins with a small amount of resistance - versus the significant resistance you describe.

View attachment 182423






images to ponder?

05a5a3a280ea375cd24e8aef0b6f4022.jpg


74492c9327063aba251c9f2fae43fd8c.jpg

bmw-e9-restomod-tyl-bok.jpg



Custom-BMW-E9-Engine.jpg
The little-/unused couplers are about 5 years old, as far as I know. One is from Schmiedmann.com. The used one comes from a car, so no idea. Will investigate the possibility they are all faulty.

Thx
 

Memo

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I recently posted a problem with this identical setup. Mine was that the fan spun freely because part #8 in the diagram which is also visible on the red fan above, was worn. The fan went along for the ride but was free to spin independent of the coupler, the coupler never engaged. Perhaps this happened previously to yours and so someone took the liberty of locking the entire setup which would explain why you cannot spin the fan by hand. You should take the setup apart to see what's what.
Will do.

Thx
 
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