Close this search box.

Cylinder Head Failure-Analysis of Diesel Engine

Cylinder Head Failure-Analysis of Diesel Engine

Cylinder head failures are one of the usual problems for every engine. It happened when the oil leaks between the cylinder head/block and liner body. But shall you directly call the pro for it? Before that, Don’t panic! COOPAL will tell you how to Keep Calm and Check the engine, and if it’s possible to do, Let’s repair!
  • Keywords: Diesel engine cylinder head, Cylinder head gasket, Cylinder head gasket
  • Summary: A coolant or oil seal failure occurs when oil or coolant leaks between the cylinder head and liner body, or between the cylinder block and liner body. Oil or coolant may leak into the adjacent coolant or oil pathway, or outward.

Cylinder headliner failures typically fall into three categories:

  • Combustion seal leaking
  • Coolant seal leaking
  • Oil seal leaking
A combustion seal failure occurs when combustion gases leak between cylinder gasket and liner combustion flange or between combustion chamber flange and cylinder gasket. Leaking gases can enter adjacent cylinders, enter into coolant or oil path, or leak outward. Coolant or oil seal failure occurs when oil or coolant leaks between the cylinder head and liner body, or between the cylinder block and liner body. The oil or coolant may leak into an adjacent coolant or oil pathway, or outward.

Cylinder Headliner-Diagnostic Procedure

The following diagnostic procedure should be performed when cylinder head gasket adhesion failure is suspected or does occur:


Before starting or disassembling the engine, visually inspect the machine and if the following reasons are found. If there is leakage of oil or coolant at the cylinder head gasket seams or adjacent surfaces, especially at the corners directly behind where the gasket meets.
  • Is the Gasket in the correct position.
  • The presence of soot from combustion gas leaks.
  • Whether the radiator, overflow tank or hose is leaking.
  • There is no coolant leakage from the coolant pump drain hole.
  • Is the radiator, fan, or wheel cover damaged and if in the correct position.
  • Whether air or coolant flow is blocked.
  • If the belt has worn or cracked.
  • Whether the pressure cap is damaged and its position is correct.
  • Is there oil mixed in the coolant.
  • The coolant level is too low or the coolant does not meet the requirements.
  • Oil level too high or too low.
  • The oil is degraded, diluted, or contaminated.
  • Correctly adjusted electronic fuel injector nozzles.
  • Are there any signs that the oil delivery is not in sync with the gear system
  • Unburned fuel or coolant in the exhaust system.

Sample Analysis

Further sample analysis of coolant and oil.

Check and Test

If the engine can operate safely, start to warm up the engine. Check all possible locations for leaks according to the previous instructions. Using the correct test and measurement equipment, check if the following have occurred.
  • The presence of white smoke, excessive crude oil, or oil mist in the exhaust system.
  • Harsh, irregular exhaust emission noise, or no ignition.
  • Air bubbles or gas in the radiator/overflow tank.
  • Coolant overflow losses.
  • High cooling system pressure.
  • Overheating Coolant
  • Low coolant flow.
  • Insufficient cab heating (air blocking).

Shut Down and Recheck

Shut down the engine. Recheck the crankcase, radiator, and overflow tank for significant differences in level, viscosity, or appearance from standard values.


Compare the conclusions from observations from the above steps with the corresponding diagnostic procedures. If the diagnostic evaluation and observations provide clear evidence that combustion gas, coolant, or oil leaking is from the cylinder head gasket sealing, the cylinder head must be removed for inspection and check the gaskets assembly.

Cylinder head gasket inspection and maintenance sequence

Cylinder Head Failure
Cylinder head gasket inspection and maintenance sequence

A – Combustion Seal (Flange)  B – Gasket Body  C – Front End of Engine

Cylinder Headliner-Inspection Procedures

Following inspection procedures are recommended for cylinder head gasket sealing failure or disconnect the cylinder head.

Historical data

View historical data by machine operation, maintenance, and repair, as well as diagnostic data. Make a note of all areas that require further inspection and analysis.

Rocker Cover

Remove the rocker cover and check if oil leaking to coolant contamination.

Record the Torque

Before removal, record the torque of the cylinder head cap screw. After removing the bolts, check the difference in cap screw length.

Remove the Cylinder head

Remove the cylinder head with proper lifting equipment to prevent damage to the cylinder head gasket. (Refer to “Removing the Cylinder Head” section in this chapter.)


Observe the surface of the removed cylinder gasket.
  • Check the burn seal (A) for the following.
  • Cam flange broken/expanded/cracked/deformed.
  • Burns/erosion of adjacent areas.
  • Ignition ring disconnected/displaced/disappeared.
  • Cam flange not sealing tightly/contains air pockets.
  • Discoloration of the area adjacent to the cam rim and cylinder pads.
  • Rough/worn/grooved cam rim surface. Inspect the gasket for following conditions.
  • Gas erosion trenches or soot deposits are generated in the combustion seal.
  • Severe discoloration/hardening/embrittlement in localized areas.
  • Oil or coolant coming out of the oilway area.
  • Local area pressure is too low.


Inspect cylinder heads, cylinder bodies, and liners for leakage of combustion gases and fluids before cleaning components. Inspect cylinders and valve passages for unusual deposits.


Clean the cylinder – Clean the cylinder head – Clean the bushings – Clean the bushings.
  • Continue with the following general and visual inspections.
  • Cylinder head (this chapter)–Check if the surfaces is flat, clean or any damage
  • If change cylinder head gasket, check cylinder head thickness.
  • Cylinder block and bushings (assembled and clamped)
  • Check the amount of bushing protrusion at each of the four-cylinder bushing locations.
  • Check the difference in bushing protrusion between cylinders.


Cylinder block –Check if the surface is flat, clean or any damage
  • Check the depth of the bushing countersink (if the bushing is removed).
  • Check the dimensions of the top crankshaft centerline. 
  • Inspect cap screw bosses; must be clean/complete.
Cylinder liners –Check that the bushing flange is flat, Check the flange for damage.
  • Check the thickness of the bushing flange (if the bushing is removed).
Cylinder head cap screws–Check the thread condition, Check the length.

Determine and repair

After completing the inspection and measurements, determine the most likely cause of the failure of the connecting elements. Make any necessary repairs to the connection components, cooling system, and fuel injection system.


Reassemble the engine according to the procedures and specifications in the appropriate maintenance chapters of this manual.
We provide Cummins Cylinder Head with Genuine Price! For more info of Cummins engine cylinder head, please contact us with part No. or part name plus engine serial No! Click Here to see our Product!