Overheating, coolant loss with no visible leak, persistent white exhaust, bubbles in the coolant, contaminated oil and misfires can all point toward a failed head gasket, but none of them proves it on its own. A thermostat, water pump, radiator, cracked cylinder head or ignition fault can cause the same symptoms. At Beach Auto & Transmission Repair in Virginia Beach we confirm the failure with cooling-system pressure testing, combustion-gas testing and compression or leak-down testing before recommending major engine work.