Sealey AK4120

This is one of three similar testers, which rely on coloured discs rising up to indicate the coolant solution. The more discs float, the higher the level of protection.

Getting a consistent reading wasn’t easy with any of these devices, but the Sealey AK4120 was the best, with good results at the key points.

Unusually for the company, the instructions aren’t very comprehensive – not good when dealing with potentially hot cooling systems.