Well more confused than normal. Last time i used the MH 333 I had coolant coming out the radiator over flow and temp got up to around 210. Figured thermostat. Had a little fun locating thermosat and gasket. Thermostat got from Napa and gasket from Wayne Steinhardt in Canada. Pulled it apart this morning and found no thermostat in the tractor. Well I had everything, so once I figured out how the replacement thrmostat went, put it back together and fired her up with the radiator cap off. Got operating temp and thermostat open. Ran for about 10 minutes everything working good, put cap on and still working good. Not sure why temp straighten out with a thermostat in it. Seen to remember being told years ago that an engine ran cooler with a thermostat than without. :?