Even the mechanic couldn't tell until we open up the engine and look inside. It clearly has been repaired at least once(probably more), the block is warped, there's nothing much the previous owner can do to save it. I can try to save it by sending the block to machine off a layer of the head so it become flat again, but then the compression will be too high as the current warp angle up to 1.6mm deep(which explain how the coolant leaked into engine room). So, I could have just change the gasket again, may be put 2 gaskets to seal off the breach temporary and sell the car again. But what will happen to the next owner? Is he going to put 3 gasket and sell the car again? So, this has to stop. I'll take the lemon, squeeze it and add a little bit of dry gin and salt to it. Replacement engine on the way.