I don't owe a PT cruiser, however I it helps: there could be blockage of debris in there, I once found plumber's white tape inside a tiny hole and around the fred outside that connection, try flushing the system and replace the liquid( as the mechanic probably did only top up) What about the accessories belt, does your battery charge OK, you should get 14. something volts, it could be loose but you would here it. Hope it helps.