I recently had some trouble with the high speed fan coming on while idling. After investigating, I replaced a leaking water pump and the thermostat. I flushed and replaced the coolant at the same time. Unfortunately I still have the fan problem. The temperature gauge on the instrument panel usually shows about half way (i.e not over-heated). I also noticed that the lower radiator hose does not get hot. I thought that I might have got a bad thermostat, that was stuck in the closed position, so I went and got another one and it still didn't fix the problem. Anyone have any ideas what else could cause these symptoms? Thanks.