Got me this car that's been reliable to a fault, and repayed the favor with a new cat, distributor& cap, plugs and sparks. And upgraded to royal purp full synthetic w/premium gas. But it leaves black spots on my brothers front bumper. Told it could be a cracked head/gasket, or the fly wheel. How do I trouble shot this... I believe fully in the DO IT YOURSELF. plus it saves a lot of money LOL