Cylinder-liner cavitation is a potentially catastrophic mechanical failure sometimes seen in diesel engines.
Cylinder-Liner Cavitation: A Cavity In Your Engine?
A cavity in your teeth that sends you to the dentist is similar to the cylinder-liner cavitation that can send your diesel vehicle to the shop.
Most diesel engines are designed with replaceable cast-iron cylinder liners that are pressed into the engine block. While this doesn’t apply to turbodiesel pickups, it affects heavy-duty over-the-road trucks and other diesels. The piston moves up and down inside the liner, while a jacket of coolant surrounds the outside of the liner to cool the engine.
When the engine is running, the pistons move vertically inside their liners several thousand times per minute. Meanwhile, the rotary motion of the crankshaft applies a thrust force through the connecting rods to the piston.
Contradictory movements cause the pistons to hammer the liners, causing significant vibration, similar to the effect of ringing a bell. This vibration can cause air bubbles to form in the coolant surrounding the liner.
When the bubbles rupture, they direct a high-pressure stream of coolant at the liner. Like a rushing river carving away a canyon wall (or Mountain Dew carving your teeth), the coolant can erode the liner until cavities form. Left unchecked, these cavities can keep growing and eventually penetrate the liner, allowing oil and coolant to mix. Once that happens, it’s only a matter of time before the engine fails.
How Cylinder-Liner Cavitation Occurs
The Role Of Engine Coolant
Prevention is the best practice when it comes to cavities, whether they’re in your mouth or your engine. That task falls on the engine coolant, and there are two ways formulators typically design engine coolant to fight cavitation.
Solving The Problem The Old-Fashioned Way
For years, formulators have added metallic salts, like nitrites and molybdenates, to coolant that attach themselves to the liner and form a sacrificial layer. When the coolant bubbles implode, the metallic salts absorb the pressure and break off from the liner surface rather than the metal itself.
Metallic salts naturally deplete over time, meaning motorists must replenish them periodically by adding a supplemental coolant additive (SCA) to the coolant reservoir, typically midway through the service interval. Unfortunately, this is often overlooked.
Solving Cylinder-Liner Cavitation The Better Way
The trend in the coolant market is to eliminate adding an SCA by formulating coolant with organic-acid technology (OAT) or hybrid organic-acid technology (HOAT).
OAT coolants don’t contain phosphates, silicates and other inorganic salts, virtually eliminating problems associated with conventional green coolants. They also last longer, which makes everyone happier.
HOAT coolants rely heavily on organic acids, but strategically use some inorganic salts to take advantage of their protective properties. A properly formulated HOAT coolant delivers long service life and excellent protection.
The chemistry of OAT and HOAT coolants passivates the liner surface, which coats it in a thin inert layer that provides protection against cavitation and corrosion. Unlike old-fashioned metallic salts, the additives in OAT and HOAT coolants last much longer, meaning you don’t have to replenish the system with an SCA.
Modern OAT and HOAT coolants also help fight problems associated with old-fashioned “green” coolants, like scaling and additive drop-out (which leads to “slime” in your coolant system) due to incompatibility issues.
AMSOIL Heavy-Duty Antifreeze & Coolant incorporates HOAT technology that is further enhanced with anti-scalant, anti-fouling and water-pump lubrication additives.
Remember To Check Your Coolant
It’s good practice to check your coolant level periodically.
Also, make sure to check the pH and glycol levels annually. Glycol is important to the level of freeze protection and the coolant’s boiling point. Over time, the water can evaporate from the system and increase glycol concentration, throwing off the coolant’s balance. Perform fluid analysis once a year for best performance.
Using AMSOIL Heavy-Duty Antifreeze & Coolant and taking care of your diesel’s cooling system go a long way toward avoiding the financial pain of fixing an engine ruined by cylinder-liner cavitation.