TYPICAL TROUBLES

RESIDUE Pink-coloured coolant is 1 a useful colour because when it dries, it leaves a pink residue that’s often easy to see. If you spot pink residue, it may not be so obvious as to the source of the leak, although the residue shown here does suggest the leaks are at the hose connections, but coolant can run down and settle away from the source.

SLACK BELT If the water pump is 2 driven by an auxiliary drivebelt, check the tension and condition of the belt.

If it’s too slack, the belt may slip, especially when the engine is under load, reducing the efficiency of the water pump and causing the coolant to increase its temperature.

CRACKED PLASTIC Water outlets 3 and thermostat housings that are made of plastic can perish, crack and leak over time. Look for coolant residue around them. Renewal usually requires the coolant to be drained or partly drained.

WORN PUMP Most water pumps 4 consist of several impellers (looks like a fan) that spin around to circulate the coolant and maintain its temperature. The bearings inside the water pump can become worn and noisy, reducing the efficiency of the pump. If the end of the pump has play in it, the bearings are usually worn, so renew it.

PRESSURE CAP FAILURE The cap 5 fitted on the top of the radiator or the expansion tank usually has a spring inside to maintain pressure in the coolant system and release it when the engine is switched off and cools down. If a valve inside the cap fails, coolant can be lost. On some vehicles, renewing the pressure cap is part of the servicing schedule.

BLOCKED TANK The expansion tank 6 can become clogged with silt, so it’s worthwhile removing it when renewing the coolant and rinsing it through with tap water. Such a problem can result in the tank becoming fully blocked, so the coolant system seems to be full, but it could actually be empty inside the engine, leading to overheating.