It's broken and probably needs a new engine.
Chances are the radiator or sump was damaged in the accident and you didn't notice the oil or coolant leaking out. Once that's gone the engine cooks. Head gasket, bearings, who knows what else.
It sounds like the body shop is right. It's too bad someone at the accident scene didn't notice all the oil and water leaking from your car.
Yes, the engine is blown. The clacking noise are the engine parts starting to get block due to friction heat because the lack of lubricant and water.
It sounds like its true. If you had no oil, your engine is toast. After you got hit, you should have looked under the car to see if anything (oil, antifreeze etc) had leaked out. You damaged your radiator and who knows what else.
Assume the bodyshop is right but take the car to another mechanic and get a second opinion. Hope you had good insurance.
I was in a car accident and was hit on the front passenger side. I didn't think the car was undrivable so I continued with my errands (after the police report was done and all). I was driving on the highway when all of a sudden the car starts slowing down even as I'm pressing the gas, then I noticed the water gauge was hot, the AC started blowing hot air and I heard this loud clacking noise and then the car turned off. It was smoking but I don't know from where. I let it cool down for a couple of hours and then I tried adding water but it went right thru spilling on the ground. I tried starting the car but nothing happened. No noise, no nothing. I had the car towed to a body shop where I was told that the engine had no oil and I blew the engine. Is this true or can it be something else? I really hope it's something else.
