I have a 2007 Subaru Impreza 2.5i and have been having some problems. A few weeks ago, I was driving and suddenly the check engine light came on, the cruise light started blinking, and the temperature gauge dropped to C. I could’ve sworn I heard something small and metal clink right as it happened. I took it to the mechanic and his diagnostic machine said it was a faulty thermostat. The next week, I took it in to get the thermostat replaced. At some point he came to tell me that it wasn’t a faulty thermostat, there was no thermostat at all. So he puts in the new thermostat and seal, then takes it for a road test. He came back like five minutes later and it was smoking like crazy. He says it’s probably a blown head gasket. The person I bought it from removed the thermostat on purpose to mask the head gasket problem. (I bought it four months ago). They used silicone to seal the thermostat gasket to the engine. He ended up removing the thermostat and trying to redo the seal on the gasket. He also replaced the seal. Since then I’ve been told it’s many different things. There’s no white smoke, it’s not leaking any fluids, my colorant level is normal, the color of the coolant is normal. When I pull out on a hill, it has trouble shifting to higher rpm’s. Other than the CEL/cruise lights being on, that issue pulling out on a hill, and overheating with a thermostat, there are no other issues with it. Without the thermostat it doesn’t overheat at all.
If anyone can help me figure this out I’d be so grateful! Thank you!