The cooling system for the Series I, II and III Land Rover works by pumping water from the bottom of the radiator into the cylinder block. The water then circulates around the block, rises to the cylinderhead and, if it is hot enough (about 75C), will open the themostat valve and enter the top of the radiator. Otherwise the water will continue circulating around the block; cooling it in the process.
As the water falls through the radiator it loses heat to the air that is passing through the radiator due to the motion of the vehicle and/or the fan.
As is common with vehicles, the Series Land Rover cooling system is sealed and therefore becomes pressurised as the temperature rises. This increase in pressure delays the possible boiling of the coolant because boiling point is lowered as pressure increases [it's science OK!]. Conversely, as the hot coolant cools, a drop in pressure below normal is possible and a safety valve is incorporated into the radiator cap to allow air into the system so preventing damage to the thin radiator core tubes.
Early Series Land Rovers had radiator caps designed to relieve excess pressure at 10lb/sq in whereas in later models this was reduced to 9lb/sq in.
The Series Land Rover was designed to operate farm machinery whilst stationary via a Power Takeoff system. This design feature resulted in the cooling system being over efficient for road purposes; the mechanical fan is often not required unless the vehicle is stationary or working hard, such as carrying a heavy load up a steep incline. Modern urban driving conditions in the UK means that your Series Land Rover will often be stationary, so the mechanical fan cannot safely be removed without replacing it with a temperature controlled electric version. In winter, it is often beneficial to fit a cover infront of the radiator to prevent over cooling on short journeys. The engine is most fuel efficient when it is hottest.
It's a good idea to flush out the cooling system before the coolant is changed and this is best done by opening the drain taps in both the radiator and engine block. Then drain out the coolant and fill the system with water through a hosepipe, whilst leaving the drain taps open. Adjust the hose flow rate to equal that draining out, then start the engine and run it for a few minutes; this enables the water pump to help drive corrosion sediment from the engine block. Finally, switch off the engine, drain the system again, close the taps and refill with coolant.
(To see previous homepages visit the Homepage Archives link)