I apologize in advance for being car-dumb. I’ve had a 1996 Saturn Coupe for a few years. The other day I was driving down the road and the overheating light came on. I pulled over and checked to see what was going on because I had just put anti-freeze in it not a week prior. It was completely empty of all liquids and I had a town truck come and get it. My brother looked at the car and said the radiator had a crack in it. I have a new one installed, drive down the road everythings fine. Next day I start it up and there is this loud knocking noise. I drive the car to work and everytime I hit the gas the knocking gets louder. I called my brother who said I would need a new engine because I have blown mine up. I’m trying to not have to shell out over $500 for this crappy car, so any help is appreciated in determining the cause.
No one, not even your brother, can determine the need for a new engine over the phone. What are the fluid levels NOW? You may need to have the car checked by a real mechanic.
From the sound of things the engine is junk. The cause of the knocking is pretty much irrelevant.
“Completely empty of all fluids” and ignoring the temperature gauge points to neglect on your part. In the future you should spend a few minutes each weekend checking those things.
The only way I can see you getting out for 500 bucks, and it’s real iffy at best, would be if you found a very reasonably priced used engine locally, on eBay, or Craigslist. You would also hopefully have a mechanically inclined brother who could change it out for you. If you have to pay a regular shop’s labor rates I don’t see it as feasible at all; unless the shop is cheap and the procured engine is even cheaper.
If you have about 140,000 on the car, it doesn’t have enough value to have it fixed. Get a good American car, like a Camry.
Well, my best theory is that you did not notice the warning light right away and that the overheating caused enough damage to essentially destroy the engine–or at least several bearings.
But, your statement about “empty of all liquids” could be very revealing. Are you telling us that there was no oil in the engine? If that was the case, then–GAME OVER. If there was no oil in the engine, then your own negligence caused the engine to die.
I had just put anti-freeze in it not a week prior
Anytime you have to add coolant, you have a problem. You need to follow up on that one every day until you are sure you don't have a problem or you have identified the problem. Not doing so can cost you a new engine.
I had just put anti-freeze in it not a week prior
I assume you again were low on coolant and likely oil. How about power steering fluid, wiper fluid, and transmission fluid? Blinker fluid? 
Have you fixed that radiator? You can’t continue to drive a car with a cracked radiator.
The failure to follow up on the coolant likely has resulted in engine damage. It is possible it has not or it may be minor, only a hands on mechanic is going to be able to tell.
My I suggest that there are several cues in your message that would indicate that you do not take very much care of your cars. I could be wrong but if this is true and you don’t like spending excessive amounts on cars, I would suggest you change that habit and start taking better care of your cars and they will give you cheaper transportation.
Thank you all for your insight. The car has well over 150,000 miles because I go to college in New Orleans, and drive home to Tennessee every few months for the past 3 years. It did have oil in it because it had a small oil leak that required I keep a check on it. I did not however check any fluids other than the oil and the coolant which was a little low so i filled it. I have a new radiator on it and as I said it was running fine after it was installed until the next day. I pulled over the minute I saw it was overheating terribly and had it towed in to shop. I really have no idea what I may have done to hurt the car so terribly. But will definately be purchasing a new vehicle this week and junking the Saturn.