This handy tool lets you pressure test the cooling system of a freshly built engine to verify the integrity of the water jacket O-rings before you install the motor. First you plug off the other openings, then install the CSPT tool, air it up to about 20 PSI (operational pressure is typically 13 PSI or 0.9 Bar) and let the engine sit for an hour or so. If it does not hold pressure, use a stethoscope to find the leak. If the leak is too slow to detect by sound, fill the block with coolant (water alone may cause rust to form), pressurize and wait for a puddle to develop. Sometimes the slow leaks are caused by your plugs, or a poor seal of the tester itself (you have to clean the water pump housing mating surface thoroughly!), so check those first. Sometimes it's just the porosity of the casting and there is little you can do, but at least you will know. The critical thing is to check for the big leaks that indicate serious internal trouble, such as a pinched water seal.Note: due to supply variability, the gauge in the picture and the gauge on the tool you receive may be different. Fits all blocks 1974 through 2012.