Our 1961 541S Jensen was having issues with over-heating, but luckily, our classic car technician Paul, put his mind to investigating the issue. He found that the wax seal in the thermostat had gotten stuck. To address this he applied a freeing agent that was left overnight so that he could ‘un-stick’ the seal the next day.
The thermostat opens to allow the engine coolant to flow through when it heats up, allowing for the cyclical movement up to the radiator, down through the radiator and round to the thermostat again. With the wax-seal seized closed, hot coolant couldn’t run through the engine, meaning it was overheating.
The thermostat works by regulating the engine temperature. As coolant flows around the engine, it collects excess heat. On leaving the engine, it travels to the radiator, where that excess heat is removed. It then makes a few more stops along its way through the cooling system and finishes back in the engine.