Replaced clutch fan in 98 isuzu rodeo. Can it be installed backwards or does it only fit on one way? Rodeo revs up now after first started until it changes gears, then it doesn't do it again until it sits and is started again. Could this be the clutch fan or maybe the torque converter?Describe your problem.
Fan blades can be installed either way. Ensure the curved(cupped)side is facing the engine.
During cold start, the engine would be running at a higher rpm due to the cold start idle up system and would gradually lower.
A good clutch fan would work at almost direct drive without slipping when started from cold and this would result in loud fan noise.
After a short while when the lubricants inside the fan clutch is evenly spread out, the fan blades would slow down till the bimetallic spring inside heats up to lock the fan. When fan blades slow down, the noise would disappear.
What you have described is the normal operational characteristics of the fan.
Your old fan was bad therefore you would not hear much noise when starting from cold.