Nightmare at Canadian Tire

We take the car into Canadian tire (first mistake).
We tell them the car is leaking coolant and smoking, need it checked as to what is causing this. We are told it will cost 59.99 for a diagnosis. Fine, check the car.
Short time later, they give me a list of things wrong with the car. I tell them I want the initial problem dealt with and nothing else. We are told the car needs a rad, it will cost almost $700.00. They tell us the car will then be fine, it will be driveable with no leaking/smoking. We tell them to go ahead and put the rad in. Three hours later, they tell us there is still a problem with the car after changing the rad. Now they tell us the engine block is cracked. They insist they could not know this without changing the rad first and retesting. I know this is not true, they should have been able to see the cracked engine right from the beginning. After alot of arguing and the sales associate swearing at my son, we were told to talk to the manager the following morning. He gave my son 2 choices, pay the bill and take the car, or walk away with no bill and no car. My son walked away, but I still have the ownership. I have since been in touch with the owner, he has said the same thing as the manager. I have refused to pay the bill. The car has been misdiagnosed, and I should not have to pay for the rad, since the car still didn't work, when they said it would. I am not sure I have any rights here, but until I find out, I will not pay the bill, nor turn over the ownership. That teaches me to go to Canadian Tire!