The OEMTOOLS 37145 Combustion Leak Tester and Head Gasket Leak Tester is ideal for finding internal engine combustion leaks and blocks quickly and easily. This Block Test Kit is designed for professional auto mechanics looking for a quality detector test. The heavy duty head gasket test is a smart addition to your OEMTOOLS toolbox. Think there is a leak in your engine block? This OEMTOOLS leak down tester will help you speed up identifying the problem so a repair can start right away. If there is a head gasket leak, bolt block pulled bolts, stud blocks, or warped sealer surfaces, the combustion leak detector fluid in the plastic tester bottle will turn from blue to yellow. Once the color changes, you will know that the pressure or leak problem is there. This block checker, head gasket leak tester, and combustion leak test also comes complete with a sturdy carrying case, perfect for any mechanic. Requires OEMTOOLS 25739 Combustion Leak Detector Fluid, sold separately.