Chevrolet Repair: 1998 CHEVEROLET MALIBU ENGINE, radiator cap, oil light

Question
I have a 1998 Cheverolet Malibu is has 173.000 miles. I had a problem with the antifreeze leaking.  I would put antifreeze in my car every other day.  When I would return home any antifreeze I put in would leak out when I stopped.  I took the car to the shop, and they replaced my radiator cap, and found the leak around my water pump hose, and stopped it. My husband drove the car last Saturday, and said he heard a knock.  He looked under the hood, and noticed that the antifreeze was low, so he put more in.  Sunday, I was about 45 miles from home, when I also heard a knock, then my oil light came on, the car started slowing down, and stopped.  When I tried to start the car again, I heard a tapping noise from the motor, and my motor was vibrating badly. Know, if I try to start the car it won't start or even turn over.  I will have the car towed to a repair shop, but first I'm trying to get a general idea of the problem.

Thanks,

Angela Henderson

Answer
It sounds like the thermostat is bad. This will cause a bubbling sound when you park it and push the antifreeze out the overflow bottle.
The engine wont turn over probably because one or more of the cylinders has filled up with antifreeze causing what is known as a "blown headgasket"
It is a little costly to repair.