Several weeks ago my engine began overheating while driving around town, and the heat would blow cold air. I figured thermostat, and so I took it down to a local mechanic and they replaced the thermostat, and Jeep ran perfect....until this weekend. Started doing the exact same thing. Took it back to the same guy, and now they're saying head gasket is leaking. However, the fluid level hasn't moved a bit. I think I'm going to take it to dealer for second opinion. Any thoughts?