3116 and 3126 Truck Engines Failures High Temperature

Valves for engines that operate in an overheated system will typically have a narrow band of oil coking near the bottom area of the valve guides’ travel. Mild adhesive and/or abrasive wear may be present. Valves in overheated systems may have deposits of oil coking on the remainder of the valve head and associated parts.

The following items are sometimes associated with high temperatures.

  • Temper colors.
  • Adhesive wear
  • Oil coking
  • Piston contact

Illustration 8 g01183488

High temperature on valve stem

(1) Bottom of Guides’ Contact

(2) Initial Adhesive Wear

(3) Oil coking

Valves in overheated systems may lose some of the alloys due to the high temperatures. If alloys have been drawn out of the valves’ material, the valve may attract a magnet.

The following items are reasons of high temperatures.

  • Overload from combustion
  • Inlet and/or exhaust system restrictions
  • Problems of efficiency in aftercooler
  • Extreme applications
  • Extreme high temperature environment

Illustration 9 g01183494

A valve attracts a magnet.

(1) Magnet

High pressures and temperatures during combustion can create damage. The system restrictions for the inlet air and/or exhaust gas temperatures can also create similar types of damage. Combustion usually creates higher pressures and temperatures that will cause greater amounts of damage to the valve and surrounding system. Plastic deformation to the valve head is known as tuliping. Tuliping is the result of higher than expected temperatures and pressures.

Illustration 10 g01183500

Valve Tuliping

High temperatures may also reduce the viscosity of the oil that allows metal to metal contact with the valve guide. Metal-to-metal contact can create adhesive wear.

Illustration 11 g01183506

Metal-to-metal wear

(1) Bottom of Guides’ Contact

(2) Oil coking

(3) Adhesive wear

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