How To Test If The Cylinder Head Is Damaged?

1、 Observe external signs

Firstly, check if there is any obvious damage on the outside of the cylinder head. Check for cracks on the surface of the cylinder head, especially near the coolant passages and bolt holes. If oil leakage or coolant leakage traces are found, it may be caused by deformation or cracking of the cylinder head sealing surface. In addition, observing the color of the engine oil, if it appears milky (similar to coffee grounds), it may be due to coolant mixed into the engine oil, indicating damage to the cylinder head or gasket.

2、 Stress testing method

Use a cylinder pressure tester to check whether the pressure of each cylinder is uniform. After removing the spark plug, connect the tester to the cylinder block, start the engine to the specified speed, and record the pressure values of each cylinder. Under normal circumstances, the pressure of each cylinder should meet the manufacturer's standards and the difference should not exceed 10%. If the pressure of a certain cylinder is significantly low, it may be due to poor sealing of the cylinder head valve or cracks in the combustion chamber.

3、 Leakage test

Perform cylinder leakage test (cylinder leakage test). Place the piston at top dead center, inject compressed air into the cylinder, and observe whether there are any bubbles coming out of the intake manifold, exhaust manifold, or coolant pot. If the intake manifold leaks, it may be due to poor sealing of the intake valve; If there is a leak in the exhaust manifold, it may be a problem with the exhaust valve; Bubbling coolant pot indicates a crack in the cylinder head connecting to the water channel and needs to be replaced immediately.

4、 Other auxiliary tests

Check if the valve clearance is abnormal. If it is too large or too small, it may cause the valve seat ring to loosen due to cylinder head deformation. By observing the interior of the combustion chamber through an endoscope, if abnormal carbon deposits or metal debris are found, further investigation of cylinder head damage is required. For aluminum alloy cylinder heads, flatness needs to be tested using a ruler and a feeler gauge. Exceeding the standard value (usually 0.05mm) is considered deformation and damage.

The above methods can comprehensively detect the condition of the cylinder head. If any problems are found, they need to be repaired or replaced in a timely manner to avoid a decrease in engine performance or more serious malfunctions.