Cooling system - draining, flushing and filling

Cooling, heating and air conditioning systems / Cooling system - draining, flushing and filling

Warning: Never work on the cooling system when it is hot.

Take care to avoid any
possibility of scalding
Draining
1 It is preferable to drain the cooling system when the engine has cooled. If this is not possible, place a cloth over the expansion tank filler cap and turn it slowly in an anti-clockwise direction until pressure starts to escape.

2 When all pressure has escaped, remove the filler cap (see illustration).

2.2 Removing expansion tank cap

3 Set the heater controls to maximum heat, then place a suitable container beneath the left-hand side of the radiator.

4 Loosen the clip and ease the bottom hose away from the radiator outlet. Drain the coolant into the container (see illustrations).

2.4a Radiator bottom hose connection - 1.3 litre

2.4b Radiator bottom hose connection - 1.8 litre

Flushing
5 After some time, the radiator and engine waterways may become restricted or even blocked with scale or sediment which can reduce the efficiency of the cooling system.

When this occurs, the coolant will appear rusty and dark in colour and the system should then be flushed. In severe cases reverse flushing may be required, although if the correct antifreeze has been in constant use, this is unlikely.

6 With the coolant drained, disconnect the top hose from the radiator. Insert a garden hose and allow the water to circulate through the radiator until it runs clear from the bottom outlet. If, after a reasonable period the water still does not run clear, the radiator can be flushed with a good proprietary cleaning agent.

7 Disconnect the heater hose from the cylinder head outlet and insert a garden hose in the heater hose. With the heater controls set at maximum heat, allow water to circulate through the heater and out through the bottom hose until it runs clear.

8 In severe cases of contamination the system should be reverse flushed. To do this, remove the radiator, invert it and insert a garden hose in the outlet. Continue flushing until clear water runs from the inlet.

9 The engine should also be reverse flushed.

To do this, disconnect the heater hose from the cylinder head outlet and insert a garden hose in the outlet. Continue flushing until clear water runs from the bottom hose.

Filling
10 Reconnect all disturbed hoses and check that the heater controls are set to maximum heat.

11 Pour the recommended coolant mixture into the expansion tank until it reaches the MAX level mark.

12 Refit and tighten the filler cap then run the engine at a fast idling speed for a few minutes whilst keeping an eye on the coolant level.

13 Stop the engine and top-up the coolant level, as necessary, to the MAX mark (see illustration). Refit the filler cap.

2.13 Topping-up engine coolant

14 After running the engine up to its normal operating temperature (electric cooling fan cuts into operation), the coolant level should be rechecked. When the engine is warm, the level of the coolant in the reservoir should be at the MAX level mark. When cool, the coolant level should be between the MIN and MAX level marks.