I own a 2002 4L SOHC Ranger. I have noticed that the level of my antifreeze in the tank remains constant. No rise or fall due to temperature. I have not been over heating. I first opened the radiator cap and the radiator was full, no harm. I then had a check engine light and the code tells me it is in the coolant system. Plenty of fluid, thermostat opens at the right temperature in boiling water, and the resistance varies on the temp sensor. All appears to be good. I put it back together and now the tank wont drain even though there is a need in the radiator. I saw taht there is another sensor next to the water temp sensor, does anyone know what that is? As far as my problem I am leaning towards a faulty radiator cap that wont let fluid in. Anyone have another opinion?

Thanks all,

 

I do know that one sensor is for the computer and the other is for the gauge in the dash. I have had a check engine light go on when one of my custumers had a bad thermostat. The computer senced that the engine was running slightly cool. Replaced the thermostat, reset the check engine light and all was well. Just my experience.

 

I see thanks. I am not sure which sensor I tested then. But the thermostat did work. I will probably take it to a garage since I need an inspection before I get pulled over. Thanks for the info though.