I have a 2001 mitsubishi eclipse rs. I have a good mechanic which i have been using for the past several years. He has always been fair and honest with me. He has recently changed my radiator about 1 1/2 month ago since it was an old radiator overheated and cracked. After the change of the radiator about 2 weeks ago the radiator overheated which he told me to put water in it and drive it to the shop. It turned out to be a loose hose. 2 days ago i was driving on the highway and it started steaming i pulled over checked under the hood it smelled like smoke. I called the mechanic and told him what had happened he suggested to me to put water and drive it to him again like the last time. Which is about 6 miles both times. I drove about 4 miles and it started splashing water from under the hood so i stopped and looked under the hood the water was bubbling in the water/compensation tank. I told the mechanic this and he told me it sounds like you blew the head gasket. So i towed the vehicle to him and he confirmed it. My question is the following. Why did the head gasket blow? Did it have to do with the radiator overheating again and if so isn't my mechanic responsible for not doing the job right the first time. Also about how much does it cost in parts and labor to change or fix a head gasket?