No mechanic can tell you if the block deck is warped or the cylinder is round with his bare eyes and if he tells you he can, he isn't much of a mechanic.
Regardless of what you may have been told, if you are losing coolant without external leaks and you are losing the heater because of air pockets being formed, you likely still have engine damage and combustion gasses getting into the cooling system. The only real accurate way to determine that is using an exhaust gas analyzer to sniff fumes at the radiator filler to measure hydrocarbons in the coolant. Those blue water chemical tests are rarely good at picking up small to medium leaks.
Saturday, April 25th, 2015 AT 8:49 AM