I have no problems with over heat of the engine. No water in the oil or oil in the water so, I do not think it's the head gasket. The van runs great! The temp gauge waw running very low, I put in a new thermo, did not help. The instrument gauge runs very low but higher than before. I checked the water temp with a food thermo, 170deg. I had a time bleeding the air out of the system when I changed the thermo. I am wonder if I still have air in the heater system. Do you have to bleed that in the back someplace? What in the world am I missing? What service manual do you recommend? Thanks for the help.