TI – 05 : Warm-Climate Engine Operation

This Advice Note was prepared in reply to a Member residing in the Middle East who enquired about engine operating temperatures.

The engine itself as a piece of machinery will be able to run at high temperatures provided that the oil pressure remains at the specified level of 60 psi when it is providing power above idling speeds. If the temperature is too high then there can be problems with pre-ignition and greater stress on the materials used for items such as the valves and pistons.  Pre-ignition is when the petrol mixture in the cylinders fires at too advanced a time resulting in a severe risk of damage to the pistons, connecting rods and crankshaft if allowed to continue. This is commonly called “knocking” and modern engine management systems have detectors to monitor this and adjust the running parameters.

In a warm climate, be sure to use good quality oil of SAE 50 grade. The radiator and cooling system on our cars operates unpressurised. This means that at 100 degrees celsius the coolant will boil which results in loss of coolant and, more importantly, incorrect cooling of the cylinders. Also, running at an engine temperature of around 90 degrees will result in fairly rapid loss of coolant by evaporation. 

The engines in the TR2 to TR4a are essentially the same but their cooling systems are pressurised. They have a standard thermostat rating of 84 degrees for winter use clearly demonstrating that the mechanics are OK at that temperature.

In the UK water-free coolant is now on the market for classic cars. I do not know what the maximum non-boiling point of these coolants is but no doubt that can be ascertained. One has to remove all traces of water from the system and the companies sell chemicals for flushing the system. Once the change has been made then there is supposed to be no risk of corrosion in the waterways of the engine and less chance of the fine tubes in the radiator becoming clogged with mineral deposits.

I have not used these coolants and from the Club’s legal position with our insurers, I can only recommend operating the cars in their original manner. If you decide to deviate from the original specification it has to be at your risk.

Bob Hobbs