Testing the pressure in the engine block is a way to identify if the engine cylinder or engine heads are leaking. Usually you want to test the pressure in an engine if you notice it is leaking engine cooling liquid, and it is not leaking via the hoses or the radiator. Testing the pressure on an engine block can be a time-consuming and difficult task, but it can be done more efficiently with the right tools.
Remove the engine and leave only the engine block out. Most major auto parts have manuals on how to remove the engine block, as it varies significantly by make and model of the car.
Cover all the coolant ports on the engine block except one. You can find universal temporary caps at most auto parts stores. Just push in the caps in all the coolant ports. The coolant ports had hoses connected to the engine that brought in coolant fluid.
Insert the air tip into the unblocked coolant port. The air tip will be included in the compression tester kit. Push it in place until it is secured.
Mix water and soap together in the spray bottle in a five-to-one ratio. Shake the bottle vigorously to create bubbles.
Connect the compression gauge to the air tip in the engine block. Connect the air hose from the air compressor to the compression gauge, and turn on the air compressor.
Spray the engine block and cylinder with the spray bottle. You will see bubbles form where there is an air leak. The compression gauge will let you know the pressure in the engine.