i was going to work today and pull over white castle drive through to get some burgers. i was sit idling waiting for my food and notice the coolant temp was up at the middle mark which is pretty high. ok let me explain on my stock coolant gauge before i get you confuse. i don't know how to read this damn line on the gauge, but anyway the lines start 1/4, 1/2, 3/4. between 1/4 and 1/2 mark would be around 180* which is where the needle suppose to be on. i was sit idling no more than 5 minutes and the needle was moving little pass the 1/2 mark. the temp outside was 53* today. during the summer time the gauge never gone up to the 1/2 mark before. i turn on the heater and it seem to drop down little bit, but still little high. when i got to work the needle was up close to the 1/2 mark. does this sound like the thermostat is not opening properly? should i go ahead and change the 'tstat.