I have a darton sleeved b18c1 with a cooling issue. When the engine warms up, the gauge on the dash starts rising above normal temp and the bottom radiator hose is ice cold almost like the thermostat is staying closed.

I removed the stat and tested it in hot water and it opens up around 200 degrees, the stat is oem and brand new

when i removed the thermostat and let it run without it, i had to jump the fan switch to get it the fan to come on. I checked the connectors and their is power. when i plug the fan connector back into the switch it over heats again

at this point im thinking the fan switch is bad on the t-stat housing, but what i dont get is when the thermostat is in, the fan doesnt come on with the sensor in it. Is it a situation where the t stat is still trying to open and the fan switch may be bad anyway?

i also put the sensor in a pot of hot water and there is no continuity between the pos/neg prongs

 

so when the tstat is in your car over heats and the fan doesnt come on?



what about with the tstat in and the fan switch jumped?