After driving my 84 Vanagon I = notice coolant coming from under the coolant expansion tank cap. I'm not sure if = the van is running hot or not. The water temp gauge doesn't work well all = the time. The cap is on tight. I just replaced the coolant and = refill tanks and caps, new thermostat, coolant, and bleed the whole = system. Is the cap supposed to open and close to allow for a pressure = release? Could I just have a bad cap? Any thoughts would be = appreciated. Thanks, Jeff