Lately I've noticed in the mornings that, while I'm trying to defog my windshield, it takes forever for the heater to get hot enough to clear it up. I've also notice that it goes cold when sitting idle, then when driving it goes warm again. Well this morning I happened to look down while sitting idle and my temp guage was in the red. When I started moving again it jumped back and forth between 3 bars and 5 bars. Is my thermostat going bad?

 

Could be thermostat. Are your fans working right?

 

there are a lot of things that can cause it to overheat- faulty thermostat, faulty radiator cap, leak, air in the system, faulty water pump. since the heater is fluctuating I am going to say it is either air in the system or a faulty radiator cap. either of those things will cause a pressure difference in the system so even if the thermostat is working it will make it seem like it is not. an easy way to test is after the car has reached standard operating temperature (3 bars) and has been there for a couple minutes touch the lower radiator hose. the top one should be really hot to the touch but if the lower one is cold than you have a problem. how is your coolant level?

 

I will have to check it at lunch. Haven't had a chance to pop the hood. Coolant level may be low because I do recall a very small coolant leak from when I bought the car.

 

Coolant level is fine, fans are running. Top hose is hot as f@#k. couldn't reach the bottom hose without burning myself lol.