Cylinder head pressure testing

After cleaning and washing, a detailed check of the cylinder head follows, and one of the ways to check is by the air pressure method. The flatness of the connecting surfaces, cracks, deformation, and wear of the cylinder head parts are checked.

The appearance of cracks in castings is the result of stress or stretching. Cracks occur due to:

defects in the casting structure during the cylinder head casting;
fatigue of the material, small cracks appear first, which spread due to constant stress;
lack of material stiffness;
mechanical damage from the impact of a solid, hard object;
the constant impact of the valve on the seat and breakage of the thin-walled cast iron;
sudden cooling of the heated part by a burst of cold water or air;
overheating due to improper operation of the engine cooling system.

Some cracks can be detected by visual inspection. However, many cannot be seen easily, so special methods and equipment are used to detect cracks in the cylinder head.

Finding a pressure crack is done in the same way as finding a hole in a tire. All coolant passages on the cylinder head are closed with plugs or closures. Compressed air is introduced into the coolant space. The air inlet is closed. Then the cylinder head is immersed in water. If there is a crack, air will come out through it and create bubbles in the water. The place where bubbles form is the place where the engine head bursts.

To cylinder head pressure testing, follow these steps:

Closing the coolant chamber

Close all coolant passages on the cylinder head with plugs and caps.

Insert the compressed air

Insert compressed air into the closed cylinder head coolant chamber. Close the air intake.

Immersion of the cylinder head

Immerse the compressed air cylinder head inside the cylinder chamber in a water tank.

Locate the cracks

Monitor the submerged cylinder head for bubbles. If there are bubbles, locate and mark the place of air leakage.