Diagnosis and Maintenance of Cylinder Head Damage in Diesel Generator Set

The cylinder head can be made of cast iron or aluminum and is an important component of a diesel generator set. It plays a crucial role in the normal operation of the diesel generator set. Once the cylinder head is damaged, the following faults may occur: power loss in one cylinder, white smoke from the exhaust, loss of coolant, and sometimes cylinder gasket leakage. Users can diagnose and repair faults based on their symptoms.

diagnostic method

This type of malfunction is usually accompanied by cylinder head cracking or possible warping. Cracking of the cylinder head may also cause coolant to enter the combustion chamber, resulting in white smoke from the exhaust. Additionally, a warped cylinder head may cause cylinder gasket leakage. Both of these faults will result in power loss of a certain cylinder. This fault can be diagnosed by conducting wet and dry shrinkage tests.

Repair method

1. Remove the cylinder head and check for possible cracks between each combustion chamber and valve guide. In most cases, cracks can only be seen by cleaning these areas with a wire brush. Cracks may be small and sometimes difficult to detect.

2. Use a ruler and a feeler gauge to check if the cylinder head is warped. The specific steps are as follows

1) First, clean the cylinder head to remove dust and grease.

2) As shown in the figure below, span the steel ruler across the cylinder head.

3) Try sliding a feeler gauge between the cylinder head and the ruler, which indicates that the cylinder has warped. Start with a 0.03mm feeler gauge, and if possible, use a thicker one. Check the curvature along the length and width diagonal directions of the cylinder head. The typical maximum warpage specification is: a warpage of 0.003 inches within a 6-inch length, or 0.007 inches throughout the entire length. Not all manufacturing plants have the same warpage specifications. Generally, the maximum warpage is between 0.003-0.007 inches.

If the warpage of the cylinder head exceeds the manufacturer's specifications, the cylinder head can be machined. This process is called milling cylinder head. Generally, professional machining workshops have suitable tools for milling cylinder heads. If the cylinder head is milled (approximately 010in), the compression ratio will slightly increase. For overhead camshaft engines, milling the cylinder head may alter the camshaft transmission ratio or chain tension.

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