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How to diagnose and repair the damage to the cylinder head of diesel generator set according to the fault phenomenon

June 27, 2022
Cylinder head can be made of cast iron or aluminum, is an important part of the diesel generator set, plays an important role in the normal operation of the diesel generator set, once the cylinder head is damaged, the following failure phenomena may occur: a cylinder has power loss, white smoke, loss of coolant, and sometimes cylinder gasket leakage. For the fault phenomenon, users can carry out fault diagnosis and repair.
Diagnosis method
This failure is usually accompanied by a cracked or possibly warped cylinder head. A cracked cylinder head may also cause coolant to enter the combustion chamber, resulting in white smoke from the exhaust. In addition, a warped cylinder head may lead to an air leak from the gasket. Both of these failures can result in a loss of power to a particular cylinder. This fault can be diagnosed by performing a wet and dry Le shrink test.
Repair method
1. Remove the cylinder head and check for possible cracks between the individual combustion chambers and valve guides. In most cases, the cracks can only be seen if these parts are cleaned with a wire brush. The cracks may be small and sometimes hard to find.
2、Check if the cylinder head is warped with a straightedge and a plug ruler, as follows
1)Clean the cylinder head first to remove dust and grease.
2) As shown in the picture below, put a steel straightedge across the cylinder head.
3) Try to slide the ruler between the cylinder head and the ruler, these places show that the cylinder has been warped, start with a 0.03 mm ruler, if possible, then use a thicker ruler. Check the warpage along the length of the cylinder head and diagonally in the width direction. Typical maximum warpage specifications are 0.003 in for a 6 in length or 0.007 in for the entire length. not all manufacturers have the same warpage specifications, but generally the maximum warpage is between 0.003 and 0.007 in.
If the warpage of the cylinder head exceeds the manufacturer's specification, the head can be machined. This process is called milling the cylinder head. Generally, specialized machine shops have the right tools to mill cylinder heads. If the cylinder head is milled (approx: 010in), the compression ratio will increase slightly. For overhead camshaft engines, milling the cylinder head may change the camshaft ratio or the chain tension.