The coolant header tank was now needing topping up at regular intervals, on this 2010 Opel Astra 1.6, and the owner was well aware that the coolant was leaking out somewhere. He had already carefully inspected the radiator and the hoses, but could see no sign of the leaking coolant.

He had also tried to detect any signs that the coolant was leaking out through the heater matrix, by having a good sniff inside, but to date had not managed to solve the mystery.

His next step was to ask me to perform a pressure test on the cooling system, with his concern being that the head gasket may be the problem.

Putting the cooling system under pressure, I was able to watch the pressure drop, and so the next stage was for me to find where the coolant was going. One clue that I spotted that the owner had not seen, was a slight pink staining on the sump near the crankshaft pulley.

After spotting this, I removed the auxiliary drive belt to get a better look at the water pump. Removing the water pump drive pulley exposed the body of the pump, and revealed that this was the source of the leak. The pump body was covered with the light pink staining, which was the giveaway sign that the pump was leaking.

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