The set is used to identify engine defects such as a cracked block, cracked head or damaged head gasket. The test is based on a change in detection fluid colour in contact with products of combustion. Apply the fluid in the jig to the radiator instead of the cap and start up the engine. If there is a crack, the fluid will respond by changing its colour from blue to yellow within 60 s (regardless of the size of defect). For accurate location, you can repeat the test while disconnecting spark plug cables one by one. The complete set includes 250 ml of detection fluid.