2001 Accord was overheating. We put in a new radiator, and thermostat. Drove great, got better gas mileage for about a week. Now having trouble starting. It acts like it's going to totally cut out, but eventually starts ( for the last week now.) A couple days ago, after starting the car, there was a strange tar-like smell and condensation started blowing out of the exhaust. It goes away after running the car a bit. Now today, the gauge reads Hot after just a few miles on the road. We were thinking head gasket, then someone brought up that it could be a sensor. Any ideas?

 

compression test it to check for damage