What in the heck would cause this!

[BrandonSK]

Sled did this to the first t-stat as well. Wife and I rode about 50 miles, the sled was running amazing then out of the blue, it overheated

 

[Captjacksparrow]

Over heating is usually what causes that, it's strange that 2 thermostats would do it but it looks like it just get hot again.

 

[BigRed800]

Were you on hard pack snow maybe not getting enough snow to the inner cooler

 

[dirtball08]

Check your water pump belt. Could be slipping.

 

[Summitric]

Yup, that thermostat was overheated.... Something caused that thermostat to open too far.... The pellets inside the thermostat were overheated and the stat opened up too far, in an attempt to allow more flow to prevent overheating. But, something else has caused the overheating, p0ssibly not enough snow on coolers.... Was it hardpark like bigred said, or is waterpump belt slipping?? If those were all okay, better check top gaskets of engine. Did you check cylinders for any signs of coolant??? Any collapsed coolant hoses??