Diesel Engine Cylinder Head Failure Analysis
Cummins, cylinder head supplier, diesel engine, diesel engine, cylinder head failure
Cylinder head failure is one of the common problems with every engine. This happens when oil leaks between the cylinder head/block and block. But would you just call a professional? Until then, don’t panic! COOPAL will tell you how to stay calm and check your engine and, if possible, let us fix it!
Keywords: diesel engine cylinder head, cylinder head gasket, cylinder head gasket
Summary: Coolant or oil seal failure occurs when oil or coolant leaks between the cylinder head and block, or between the cylinder block and block. Oil or coolant can leak into adjacent coolant or oil passages, or leak outward.
Cylinder head lining failures generally fall into three categories:
- Combustion seal leak
- Coolant seal leaking
- Oil seal leakage
Combustion seal failure occurs when combustion gases leak between the cylinder gasket and liner combustion flange or between the combustion chamber flange and cylinder gasket. Leaking gas can enter adjacent cylinders, enter the coolant or oil circuit, or leak outside. Coolant or oil seal failure occurs when oil or coolant leaks between the cylinder head and block, or between the cylinder block and block. Oil or coolant can leak into adjacent coolant or oil passages, or leak outward.
Cylinder Head Liner Diagnostic Procedure：
When cylinder head gasket adhesion failure is suspected or actual, the following diagnostic procedure should be performed:
Examine
Before starting or removing the engine, visually inspect the machine for the following causes. If there is oil or coolant leaking from the cylinder head gasket seams or adjacent surfaces, especially at the corners directly behind where the gaskets meet.
- Is the gasket in the correct position?
- Presence of soot from combustion gas leaks.
- Check for leaks in radiator, overflow tank or hoses.
- There is no coolant leakage from the coolant pump drain hole.
- Radiators, fans or wheel housings are not damaged and are in the correct position.
- Is the flow of air or coolant blocked?
- If the belt is worn or cracked.
- Is the pressure cap damaged and is it in the correct position?
- Is there oil mixed in the coolant?
- The coolant level is too low or the coolant does not meet the requirements.
- Oil level is too high or too low.
- The oil is degraded, diluted or contaminated.
- Properly adjusted electronic injector nozzles.
- Are there any signs that the oil delivery is out of sync with the gear system?
- Unburned fuel or coolant in the exhaust system.
Sample analysis
Further sample analysis of coolant and oil.
Inspection and testing
If the engine can operate safely, begin warming up the engine. Check all possible locations for leaks according to the previous instructions. Using the correct test and measurement equipment, check whether the following conditions occur.
- There is white smoke, excessive crude oil or oil mist in the exhaust system.
- Harsh, irregular exhaust noise, or no ignition.
- There are bubbles or gas in the radiator/overflow box.
- Coolant overflow losses.
- Cooling system pressure is high.
- Coolant overheated
- Coolant flow is low.
- Insufficient cab heating (air blockage).
Shut down and recheck
Turn off the engine. Recheck whether the fluid level, viscosity or appearance of the crankcase, radiator and overflow tank differ significantly from standard values.
Compare
Compare the observations from the above steps with the corresponding diagnostic procedures. If diagnostic evaluation and observation provide clear evidence that combustion gas, coolant, or oil leaks are coming from the cylinder head gasket seal, the cylinder head must be removed for inspection and the gasket assembly inspected.
Cylinder head lining inspection procedures:
The following inspection procedures are recommended for cylinder head gasket seal failures or disconnected cylinder heads.
Check the historical data
Turn off the engine. Recheck whether the fluid level, viscosity or appearance of the crankcase, radiator and overflow tank differ significantly from standard values.
Rocker cover
Remove the rocker cover and check for coolant contamination from oil leaks.
Record torque
Before disassembly, record the torque of the cylinder head screws. After removing the bolts, check for differences in cover screw lengths.
Remove cylinder head
Use appropriate lifting equipment to remove the cylinder head to prevent damage to the cylinder head gasket. (See the “Removing the Cylinder Head” section in this chapter.
Observe
Observe the surface of the removed cylinder gasket.
Check combustion seal (A) for the following conditions.
- Cam flange broken/expanded/cracked/deformed.
- Burns/erosion in adjacent areas.
- Ignition ring disconnected/displaced/disappeared.
- Cam flange is not tightly sealed/contains air pockets.
- Discoloration of the cam rim and area near the head gasket.
- Cam rim surface rough/worn/grooved.
- Check the gasket for the following conditions.
- Gas erosion grooves or soot deposits are created in the combustion seal.
- Localized areas of severe discoloration/hardening/brittleness.
- Oil or coolant is flowing out of the oil gallery area.
- The local area pressure is too low.
Examine
Check the cylinder head, cylinder block and liners for combustion gas and fluid leaks before cleaning components. Check cylinder and valve passages for unusual deposits.
Clean
- Clean cylinder –
- Clean cylinder head – Clean bushing – Clean bushing.
- Continue with the following general inspection and visual inspection.
- Cylinder Head (Chapter) – Check surfaces for smoothness, cleanliness or any damage
- If replacing the cylinder head gasket, check the cylinder head thickness.
- Cylinder block and bushing (assembly and clamping)
- Check the amount of bushing protrusion at each four-cylinder bushing location.
- Check for differences in bushing protrusion between cylinders.
Examine
Cylinder Block
- Check surfaces for smoothness, cleanliness or any damage
- Check the depth of the bushing counterbore (if the bushing was removed).
- Check the dimensions of the top crankshaft centerline.
Inspect cap screw bosses; must be clean/complete.
- Cylinder Liner – Check the liner flange for flatness and check for damage to the flange.
Check the thickness of the bushing flange (if the bushing was removed).
- Cylinder head screws – Check thread condition, check length.
Identify and fix
After completing inspections and measurements, determine the most likely cause of the connecting element failure. Make any necessary repairs to connecting components, cooling system and fuel injection system.
Recognation
Reassemble the engine according to the procedures and specifications in the appropriate maintenance section of this manual.