Before I did the cap, I replaced all the plugs and coils, replaced the water pump, and I've put some bar's leak/stop leak solution in the coolant reservoir before and it seemed to help for a while. Idk what to do. The car has 252 k miles, I bought it used a year ago with 187k miles. Now she is going through coolant like nobody's business. When I replaced the cap yesterday it worked great for a few hours. How do i detect where the leak is coming from?