How do you tweak a fan clutch?

[sturgeon-phish]

Many posts speak of modifying the existing fan clutch spring to lower fan engagment temp. A post long ago told how to do it but I can't find the post. Would someone tell me how to do the mod and the results, good and or bad with the mod that you have experienced. Thanks
Jim

[autocrosser]

Just take the clutch off and verify the movement of the spring when you apply a little heat to it. I believe it expands when heated. The below info is based on my memory so verify which way you need to go.

Remove the little bit of silicone holding the spring tab in the slot. You can shave a little off the bottom of the slot that holds the spring or I believe there is a little tab in the slot that can be shaved off. You could also very slightly bent the spring tab that goes in the slot. I did both and went too far. The whole object is to reposition the clutch shaft to off set it a little (VERY, VERY LITTLE) so that when it does heat up and move it will be in a slightly more engaged position. I believe I bent the spring tab a little to the right which allowed the spring to move counter clockwise.

You may have to make it a trial and error job. My first attempt resulted in the clutch being locked up all the time. I took one more time to get it right. Remember it takes very little movement to do the job. If you were to heat the clutch to 200 deg you could see just how much movement the spring makes and that will give you a idea of what is needed.

When you are finished lock the spring back down with a little silicone in the slot. My truck never exceeds 200 deg with a 8000lb load going up steep mountains in 95 deg weather. It doesn't go fast up the hill but it goes.