Press release [PDF; 38 KB]
Press release [RTF; 39 KB]
Time and time again, engine specialists in customer service are confronted with cylinder liners whose outside surfaces are literally eaten away. Diagnosis: cavitation (lat. cavitare: to cave out), also known as pitting corrosion. What causes this type of damage? And what can be done about it?
Cylinder liners in commercial vehicle engines are generally wet bushings that are washed with coolant during operation, which effectively carries off the heat of combustion. One disadvantage of this design: The piston motion in the combustion engine causes variations in pressure, which are transferred to the surrounding water jacket.
When the cylinder wall moves back during an oscillation phase, a vacuum is induced in the coolant, which can lead to the formation of vapor bubbles. When the water pressure returns, these vapor bubbles can implode and “blast out” individual atoms from the surface of the cylinder liner: pitting corrosion is the result.
Cavitation damage occurs particularly in engines running at temperatures between 50 and 70 degrees Celsius. At higher temperatures (90 to 100 degrees Celsius), the higher water pressure prevents vapor bubble formation. A defective thermostat or viscous clutch in the fan cooling system can also drop the engine temperature so severely that the cooling system cannot develop positive pressure.
“Once the cylinder surface is damaged by cavitation, it provides points of attack for additional cavitation—and for corrosion. Critical engine damage is impending,” Arnd Franz, General Manager of MAHLE Aftermarket, explains the consequences. Pitting corrosion, however, can be prevented with quality products and vigilant engine maintenance. Low-quality cylinder liners with high production tolerances have much greater motion than quality products from MAHLE. The increased vibrations often cause cavitation damage. The same effect is caused by excess piston clearance. Low-quality materials and distilled, strongly alkaline or acidic coolant can also lead to cavitation damage.
Working closely with the engine and automotive industry, MAHLE engineers have developed engine components with minimal susceptibility to cavitation. Smooth-running pistons and low-vibration cylinder liners, for instance, together with minimal production tolerances, guarantee reliable functionality over the entire life of the engine.
For further information:
MAHLE Aftermarket GmbH
Andrea Arnold
Corporate Communications
Pragstraße 26 - 46
70376 Stuttgart
Germany
Phone: +49 (0) 711/501-13124
Fax: +49 (0) 711/501-13700
andrea.arnold@mahle.com