What are the reasons for cylinder heads cracking?

In winter, when the temperature is low, diesel engine cylinder heads are prone to cracking, causing leakage. The main reasons for this are as follows: 

1. Add cooling water immedietely after starting. After starting the diesel engine, the temperature inside the engine immediately rises. If cooling water is added at this time, the cylinder block and cylinder head will cool down rapidly, causing cracks due to cold shrinkage. 

2. After shutdown, cooling water was not fully drained. The water inside freezes, and becomes ice. After freezing, the volume would increase, resulting in expansion and cracking of the cylinder body and cylinder head. 

3. When the diesel engine is running, cooling water would be added if it is insufficient or the engine temperature is too high. It might cause undercooling shrinkage of the cylinder block and cylinder head would also crack. 

4. The diesel engine runs for a long time and the temperature inside the engine is high. After stopping, immediately drain the high-temperature water. It can cause high-temperature parts to suddenly crack when exposed to cold air. 

5. Using a pressure reducer to stop the engine would cause the high-temperature cylinder head to suddenly encounter cold air and crack. 

There are the following methods to prevent cracking of various types of cylinder blocks and cylinder heads: 

1. Before starting the diesel engine, warm water should be added to the water tank. In severe winter, hot water should be injected 2-3 times. It is best to start when the water flowing out of the drain valve is about 30-50 ℃. 

2. When the diesel engine runs for a long time, wait for about half an hour after shutdown, and then drain the cooling water when the engine temperature drops to 40-50 ℃. It is best to use a thin iron wire to poke through the drain valve switch after draining the water to prevent sediment from blocking the drain valve. 

3. When the diesel engine runs excessively hot and lacks water, it should be allowed to idle at low speed for 10-15 minutes before slowly adding cooling water.