Hello, Recently my headgasket had blown. I took it to a auto shop for repairs. They replaced these parts: Head gasket, timing belt,spark plugs,throttle position sensor, and ignition coil. Now when I drive and turn the AC on the car idles up and down and pulls. The car runs normally when I turn the AC off. The engine started to overheat on Friday. I notice that the the coolant was completely gone out of the radiator and the coolant reservoir. I added coolant to the radiator and the coolant reservoir a couple days ago. I check the radiator today and the radiator looks drained. There is still plenty of coolant in the coolant reservoir. Can someone tell me what could be wrong with the idle and radiator issue?