Re: high pressure in cooling system hours after shutdown
That sounds strange. A failed open thermostat would cause low coolant temps and a failed closed thermostat overheating. Also the radiator cap would relief pressures over 18 PSI. As soon as the engine cools down, the coolant volume reduces and an underpressure should draw back coolant from the overflow reservoir. So can it be that the radiator cap doesn't open and causes too high pressure which takes longer to reduce?