How to Avoid Liner Pitting

Older engines may be vulnerable

Does your diesel engine have a replaceable cast iron cylinder liner? If so, it may be vulnerable to accelerated corrosion as a result of liner pitting. Supplemental Coolant Additives (SCAs) are effective to prevent liner pitting when used in the cooling system according to recommended concentrations. SCAs form a protective film on the coolant side of the cylinder liner, allowing a layer of protection against damage from the implosion of air bubbles caused by high frequency vibrations created during the normal operation of a running engine.

Formulations differ with the additive package that’s blended into the ethylene glycol. All of these additives fight rust, scale and corrosion but may have different chemical compositions. In diesel engines the additives also protect wet cylinder sleeves from cavitation

SCA Protects Liners from Pitting

The Supplemental Coolant Additive forms a protective film on the coolant side of the liner and transforms soft ferric oxide or rust into extremely hard FE3O4. Fleetguard’s DCA4 SCA provides optimal liner pitting protection and contains nitrite and molybdate. This protective layer makes it virtually impossible for pitting to occur.

Follow a few simple rules to avoid problems

1. Check the SCA level each time you change the oil.
   Liners are protected from pitting by elements in the SCA. Liner pitting can develop within 500 hours of operation under severe conditions when plain water is used as a coolant.
2. Be careful to avoid topping off radiators higher than the fill neck.
   When you top off fluids, the expansion area in the top tank is eliminated. Coolant is then forced out of the system when the engine warms up, and the SCA level is diluted.
3. When you add make-up water, always add SCA.
   Maintain the SCA levels to protect cylinders from liner pitting.
4. Correct proportions are assured when you use a coolant premixed with SCA.
   The ratio of coolant to SCA can vary with cooling system capacity, and it is the same for both the initial fill and topping off. To ensure that proportions are always correct, use a coolant premixed with SCA.

Warning Signs

• If you need to add large amounts of water to increase fluid levels, chances are that SCA was not added every time water was, unless you’re using a premixed coolant that contains SCA.
• If there’s no coating on the liners, it’s a sign of low SCA levels.
• If your oil analysis records show traces of potassium, it’s possible that coolant has
  leaked into the oil, and oil has leaked into the coolant already.