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Full-Stop Liners
Full-stop liners, also called bottom-stop liners , are a solution to the problem of top-stop flange and counterbore damage. The liner distributes the axial load applied to the liner (from the clamping force of the cylinder head) onto a top- and bottom-stop flange surface Figure 48. The potential damage decreases because the clamping force load, applied axially through the liner, is distributed over two separate surfaces at each end of the liner. The top flange is relatively smaller in diameter than its bottom-stop pilot pad because it supports less load and divides the load distribution to a bottom-stop pilot pad. In fact, the liner flange load is reduced during combustion events when the liner walls bulge or swell slightly, causing the length of the liner to shorten and reducing the axial load on the flanges.
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Technicians Tip |
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Diesel engines have a unique problem known as cavitation erosion , which is caused by the collapse of tiny water vapor bubbles formed when coolant vaporizes on hot cylinder walls. Cavitation erosion produces deep holes in liners and cylinder walls and results in coolant leaks into the engine or combustion leakage into coolant. Liner vibration and flexing during the combustion phase and the power stroke are the primary causes of vapor bubble formation. These vapor bubbles collapse when cooled or when pressure increases around the bubble. Pressure exerted by the force of bubble collapse is reported to be as high as 60,000 pounds per square inch (psi; 413,685 kilopascal [kPa]). The force of vapor bubble implosion against cylinder walls, cylinder liners, and other components can eventually cause pitting and quickly destroy cylinder walls and liners. Diesel engines therefore require the addition of supplemental coolant additives containing nitrite. These additives form a sacrificial barrier to protect the coolant side of the cylinder wall and liner to protect against pitting. |
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FIGURE 08-48: Note the top flange and lower pilot stop of this full-stop or bottom-stop liner.
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