Recently had heat exchanger replaced on my 08 Nytro. Had a local shop replace heat exchanger and track, due to stud ripping through it. Local shop, good reputable mechanic fixed it correctly.....very labor intensive. It seems now, that through riding, as it heats up, pushes coolant into the overflow, then never sucks it back in as it gets back to normal temps. The overflow then pushes out the excess, and by about 100 to 125 miles, not enough coolant in radiator to keep it cool. Fan is wotking as it should. I know this is a lot of info, but what could be the problem. Sam