E34 fan clutch bimetallic strip mod

[ktteoh]

folks, my local mechanic (without checking with me) did this.

he used a screwdriver to bend the bimetallic strip on the fan clutch outward (towards the radiator) - i think this makes the clutch engage earlier?

the temp gauge is now about two notches below mid-point. however the engine roar is louder - due to tighter fan engagement?

my questions:
1. how do i know if the clutch still behaves normally during cold - is it supposed to free wheeling only when the engine is cold from overnight stop?

2. any reliability issue?

3. anyone thought of this before?

[shogun]

That seems to be a real backyard hack mechanic.
In case you have the Behr clutch, that bimetall is clipped in 4 places.
How can be bend it?
Here some pics.
http://bmwe32.masscom.net/johan/fan_clutch/fan_clutch.html

Better try to refil the clutch with the Toyota silicone oil, part number 08816-0300
http://members.rennlist.com/blueshark/page11.html

How to test a fan clutch:
http://www.mwrench.com/Whitepapers/FanClutchtest.pdf

1. how do i know if the clutch still behaves normally during cold - is it supposed to free wheeling only when the engine is cold from overnight stop?
No, it depends on the temperature, not only overnight

2. any reliability issue? maybe it always runs now

3. anyone thought of this before?
Never, and I will not do it

[ktteoh]

shogun, mine's a behr clutch.

i'm not sure which way he bent it. i'm assuming when the strip is hot, it bends in one direction - pushing the ping in (or out). (what my mechanic) is too slightly "pre-bent" the strip.

do you know how the bimetallic strip bents when hot and how does that actuates the clutch?

if this isn't right, i need to know how to "straighten" the strip and by how much.


That seems to be a real backyard hack mechanic.
In case you have the Behr clutch, that bimetall is clipped in 4 places.
How can be bend it?
Here some pics.
http://bmwe32.masscom.net/johan/fan_clutch/fan_clutch.html

Better try to refil the clutch with the Toyota silicone oil, part number 08816-0300
http://members.rennlist.com/blueshark/page11.html

How to test a fan clutch:
http://www.mwrench.com/Whitepapers/FanClutchtest.pdf

1. how do i know if the clutch still behaves normally during cold - is it supposed to free wheeling only when the engine is cold from overnight stop?
No, it depends on the temperature, not only overnight

2. any reliability issue? maybe it always runs now

3. anyone thought of this before?
Never, and I will not do it

[shogun]

I have not disassmbled it by myself. Maybe he knows a trick more than we for hot climate fans and that might work, although that is more backyard technic.
Here from my website the function of the fan clutch.
http://www.kfz-tech.de/ViskoluefterZ.htm

click below the pic on
motor kalt =cold engine
motor warm = warm engine
motor heiss = hot engine
and the last click is a cross section.

There you see what happens in the different phases.

[attack eagle]

ouch, isn't there the possibility of it shedding blades if it were to be engaged constantly as well?

[Ferret]

ouch, isn't there the possibility of it shedding blades if it were to be engaged constantly as well?

Definitely, especially if it's an old one....