Causes and possible consequences of valve failures in the engine

The valve doesn't close properly? Possible causes include incorrect valve clearance setting, or failure to rework the valve seat ring or valve guide in the center. Too large or too small a valve gap can also be fatal.

Send your inquiry

*Name
Format error
*E-mail
Format error
*Phone/WhatsApp/Skype
Format error
*Company Name
Format error
*Content
Format error

Causes and possible consequences of valve failures in the engine

◆Installation and adjustment errors

Incorrect valve clearance settings

Cause: The valve clearance has been set too tight or the maintenance intervals have been exceeded.

Result: The value no longer closes properly. Combustion gases flow past the valve seat and heat up the valve head. This causes the valve head to overheat and burns through in the seat area.

◆Valve springs are not installed correctly

Cause: Spring is not inserted correctly during installation. The inclined spring creates a lateral bending moment (M) on the stem.

Result: The resulting alternating bending stress eventually causes the valve rod face to fracture and damage the valve conduit.

◆Hydraulic tappet is not installed correctly

Reason: After the tappet is installed, the minimum waiting time (at least 30 minutes) before starting the engine is not observed. As a result, excess oil in the tappet working area did not have enough time to drain.

Result: If the engine starts too early, the valve will strike the piston and may bend or break.

◆Machining error

Valve seat ring or valve guide is not aligned

Cause: Off-center reprocessing of seat or guide.

Result: Valves fail to close properly, overheat, and burn through the seat area. Fatigue fracture in the fillet area may also occur due to unilateral stress on the valve head.

◆Valve duct clearance is too large

Cause: Excessive valve duct clearance due to excessive valve duct wear or excessive reaming during repair.

Result: The influx of hot gas leads to the accumulation of carbon in the stem guide area. The valve hardens and does not close properly, resulting in seat overheating (burn or jet channel).

◆Insufficient valve duct clearance

Reason: When replacing the valve catheter, the diameter of the catheter is too small.

Results: The valve stem in the guide rail has insufficient lubrication, stiffness and stuck. Indirect damage may occur, such as overheating of the valve head or seat area.

◆Install worn parts

Cause: Old, worn valve pins were used during valve replacement.

Result: If a worn valve pin is reused, the clamping system will loosen during operation. This can cause friction corrosion of the stem and weaken the valve in that area. This can lead to vibration fatigue failure.

◆Installing damaged rocker arms/finger type rockers

Cause: Forces are applied eccentrically from the rocker arm to the skirt end face of the valve.

Result: Unilateral wear occurs on the stem and the skirt end. The lateral force on the valve stem caused by the eccentric application of force causes fatigue fractures in the area of the clamping system.

◆Install elbow valve

Cause: A bent valve stem will cause unilateral support of the valve seat on the seating ring.

Result: The unilateral stress causes alternating bending stresses and fatigue fractures in the fillet radius at the transition to the stem.

◆Burning default

Valve overstressing due to combustion defaults

Cause: Significant increased pressure and temperature loads occur in the combustion chamber as a result of combustion defaults.

Result: The valve head cannot withstand the high thermomechanical loads and bends inwards. This results in so-called tulip formation and causes fractures in the area of the valve head.