464-4668 Exhaust Valve 4644668 For Diesel Engine Parts C15

Causes:

The exhaust valve directly withstands the scouring and impact of high-temperature, high-speed combustion gases. The 45° sealing cone surface that contacts the valve seat is the core sealing area. After prolonged operation, pitting, dents, and erosion will appear on the cone surface, especially in areas of localized overheating, and the normal wear band will widen, leading to poor cylinder sealing, decreased compression ratio, and insufficient power.

Repair:
The valve must be removed and precision ground on a professional valve grinder at its original angle until a complete, smooth, and defect-free sealing band is obtained. Simultaneously, the mating valve seat must be ground or replaced, and the width and position of the contact marks should be checked using red lead oil or Prussian blue to ensure a perfect seal.

Causes:

The valve stem moves back and forth rapidly within the valve guide, relying on the splashing of engine oil for lubrication. If the oil quality is poor, if carbon deposits are mixed in, or if the alignment of the guide is improper, it will cause scratches, pulls or non-uniform wear on the stem in the form of a "clock mouth" shape, resulting in the valve movement being stuck, the valve closing not tightly, and an increase in oil consumption or oil leakage.

Repair:
Use a micrometer to measure the diameters of the upper, middle and lower parts of the valve stem, and check their roundness and wear. At the same time, use an internal diameter gauge to measure the inner diameter of the valve guide. Calculate the mating clearance between the two. If it exceeds the standards specified in the Caterpillar Maintenance Manual, which are usually very strict, new valves and new valve guides must be replaced simultaneously, and ensure that the inner hole size and roundness after the valve guide is pressed in meet the requirements.

Causes:

This is the most severe high-temperature area of the exhaust valve, especially the "neck" where the disc surface meets the stem. When exposed to exhaust gases exceeding 800°C for a long time, the material will undergo thermal fatigue and creep. Common faults include burn marks on the edge of the disc surface or small radial cracks in the neck. Once this occurs, it is highly likely to cause the valve to break, resulting in a catastrophic failure.

Repair:
There is no possibility of repair. Every time during the inspection, a magnifying glass or magnetic particle inspection must be used to carefully examine all the valves, especially this area. Any tiny abraded gaps, cracks or abnormal color changes, such as severe local oxidation, must be immediately scrapped and replaced with brand-new genuine valves. This is the key to preventing major engine accidents.

Causes:

The lock clip groove is used to fix the valve spring seat and withstand alternating impact loads. If the lock clip is installed improperly or the gap is too large, it will cause wear and chipping at the edge of the groove. The end face at the tail end contacts the rocker arm or the bridge, and due to poor lubrication or impurities, it will result in scratches and depressions.

Repair:
Visual inspection is conducted to check if the edges of the lock catch groove are sharp and if there are any damages. Wear on the groove can lead to the risk of the lock catch coming out. Such valves must be replaced. For minor wear on the tail end face, it can be repaired and smoothed on a professional grinding machine, but the grinding amount must be strictly controlled to ensure that the total length and "installation height" of the valve are within the standard range. Otherwise, it will seriously affect the spring compression force and valve lift. Severe wear requires direct replacement.