Timing Belt/Radiator/Water Pump/Heater
Car: 2003 Kia Rio
Previous Problems: Timing belt broke and caused $1,500.00 in repairs. The "head" had to be remachined, valves and cylinders needed to be replaced or repaired. I drove the car for a week. Then the radiator cracked. This cost $400 to replace. While replacing the radiator the mechanic showed me that my water pump was making a noise most likely to the "ball bearings" going bad, so I had that replaced. This cost another $400.00.
Current Problem: I just got my car back yesterday. While driving home I had the air conditioner on and it seemed that the temperature gauge on my dashboard was going up. I couldn't really tell 'cause it’s a short ride home. (I turned it on just to see if my car would still idle low with it on, after all these repairs.) Today however it was cold in the morning so on the way to work I was waiting for the temperature gauge to go up to the middle so I could turn the heater on. After going 26 miles at 65-70 mph it didn't budge but a tiny bit. I thought it was kind of moving, so just to see if my engine was hot I turned on the heater. It blew cold air and my temperature gauge started going back down. (Not that it had far to go down.) When I got to work, I opened the hood to check to see if the engine was hot. It was hot but really didn't seem too hot. I could touch the radiator with my bare hand and it was warm.
I called the mechanic shop and they said it could be the heater core. What I want to know is if this problem could have stemmed from incorrect repairs. If you can't tell I know nothing of auto mechanics. Yet, I have found out that in some way these items are all closely related. (That sounds stupid I know.) Also, is this something that I could change out myself? If it is not changed will my car stop working and fall apart? Is it the thermostat? Is the thermostat something I can change?
Help me please!