Damaged valve lifters - why is their efficiency so important?
Machine operation

Damaged valve lifters - why is their efficiency so important?

Damaged pushers - signs of malfunction

Valve lifters are one of the engine components that play a key role in the combustion of the air-fuel mixture. They actuate the valves, allowing fuel and air to enter the cylinder, and the subsequent discharge of exhaust gases left over from the process.

The duty cycle of the valve lifters must match the duty cycle of the piston. That is why they are driven by rotating camshaft cams. This system is fully synchronized at the factory, but it can be disturbed during engine operation. The problem is that the so-called valve clearance, that is, the corresponding distance between the camshaft cam and the tappet surface. The gap must be maintained due to the physical properties of the metal, which expands at high temperature, increasing its volume.

Incorrect valve clearance can have two consequences:

  • When it is too low, it can cause the valves not to close, which means the engine will lose compression (uneven operation of the unit, lack of power, etc.). There is also accelerated wear on the valves, which lose contact with the valve seats during the operating cycle.
  • When it is too large, it can lead to accelerated wear of the valve plane, while the wear of other components of the gas distribution system (cams, levers, shaft) is accelerated. If the valve clearance is too large, the operation of the engine is accompanied by a metallic knock (it disappears when the temperature of the unit rises, when the metal parts increase in volume).
Damaged valve lifters - why is their efficiency so important?

Damaged pushers - the consequences of negligence

The vast majority of modern automotive engines use hydraulic valve lifters that automatically adjust valve clearances. Theoretically, the driver of the vehicle thus gets rid of the need to control and manually set the valve clearance. However, hydraulic tappets require engine oil with the correct parameters to operate effectively. When it gets too thick or dirty, the tappet holes can become clogged, causing the valve to not close. An engine operating in this way will make a characteristic noise, and valve seats may burn out over time.

Vehicles with mechanical valve lifters require periodic clearance adjustment as recommended by the engine manufacturer. Adjustment is mechanically simple, but it is recommended to perform it in a workshop. To measure the gap, a so-called feeler gauge is used, and the correct gap size is achieved by adjusting the screws and using washers.

Typically, gap adjustment intervals in mechanical pushers range from tens to one hundred thousand kilometers. However, factory recommendations need to be revised if a decision is made to install a gas system in a car. Then there is a need to check and adjust the play more often. LPG engines are exposed to higher temperatures. In addition, the process of gas combustion itself is longer than in the case of gasoline combustion. This means a greater and longer thermal load on the valves and valve seats. The gap adjustment intervals for cars equipped with a gas installation are about 30-40 thousand km. km.

The lack of regular clearance adjustment in any engine with mechanical valve lifters will sooner or later lead to significant wear of engine compartment parts. However, even in engines that have been tuned regularly, valve lifters may need to be replaced over time.

Replacing valve lifters - when is it necessary?

The replacement procedure depends on the design of the engine, and the types of valve lifters also differ. Usually, after removing the valve cover, it is necessary to remove the camshaft so that the pushrods can be removed and replaced with new ones. In some engines, after replacement, it will be necessary to adjust the new pushers, in others they should be filled with oil, in others, such measures are impractical.

It is important to replace all gaskets with new ones during repairs and check the condition of other timing elements. If the engine has been operated for some time with incorrect valve clearances, the camshaft lobes may be worn. It is also worth looking at the condition of the shaft itself.

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