I have a 98 with 4800 miles that I have started getting heat build up. The fan will come on the gauge never goes beyond 1/2 and seems to rise at the apropriate times and yet lately on longer rides I get excessive heat coming all the way up to the seat. I also notice that the hotter it gets the harder the shifting is?? My direction was the clean out the cooling system in hopes it has rust?? Any thoughts?