Water pump pulley fell off, is engine destroyed?

Overheating a motor will cause it to fail in myriad ways later. Count on all the seals and gaskets blowing out (when they otherwise wouldn't.) That's even if the metal bits have not warped or failed in some other way. It can also cook other devices under the hood. That motor is toast.

How exactly did you "check the radiator cap"? Usually on a car unscrewing that after the car has been driven is a terrible idea since it may blow up in your face, and the coolant can cause severe burns. If you actually did that, and the coolant wasn't hot, that told you the cooling system was not working, at all, which should have been sufficient clue not to turn it back on and keep driving.

 

You're saying the water pump pulley right there at the front right of the motor if you're standing on the right side of the car looking down at the front of the motor that has nothing to do with the camshaft That's just a pulley that's mounted to the water pump You could get some more bolts line that back up and put them in as a short fix if the bolt holes are not allowed too badly and be on your way You probably didn't do any serious overheating but you need not be cranking on it while this belt is half hanging or this pulley is barely held on by a boat or flopping around No need to be doing that If you absolutely positively have to go a short way You need to make sure you take the pulley off whatever is holding it's probably barely hand tight and take the belt off put it in the back of the car now see if the car starts because it's cold and been sitting. And if so drive it home or whatever but you need to get a pulley and the belt back on and I believe this is a clutch driven affair so you need to make sure all that's in order on the front of the water pump

 

Yeah the engine coolant not hot should have been a tip off. It means there is no coolant circulation. very bad. I would have looked at the water pump belt as this is what happens when the belt falls off. Pretty sure you must have smelled something burning as it was in severe over heat.

Knocking Sounds like the engine bearings are seized from the heat. Probably piston wrist pin #2 went first it seems to be the first to go on an overheat it fails alot under no engine oil in the engine and sometimes throws the piston thru the block. Seen a bunch of those.

Its a disastrous system they use in the G2 with no temp gauge to monitor engine temps so by the time the engine light comes on the engine is destroyed. Same if the belt falls off. Horrible design.

I was just posting here yesterday about coolant/belt questions and told that poster the same thing. It is ultra important to make sure the water pump system/the belt/the idler bearing/weep hole and the rad is full not the overflow tank on this car as they are all extremely important to the engine and your wallet.

White smoke is head gasket blown from the over heat the aluminum head warps real quick and lets coolant into the combustion chamber. That alone means the engine will have to be replaced. But you have knocking too which is a blown bearing/bearings.

I'm afraid your engine may be toast.