Water can be introduced into the fuel supply through poor maintenance (loose or open fuel tank caps),
contaminated fuel supply or condensation.
Condensation is particularly prevalent on units which stand idle for extended periods of time, such as marine
units. Ambient temperature changes cause condensation in partially filled fuel tanks.
Water accumulation can be controlled by mixing isopropyl alcohol (dry gas) into the fuel oil at a ratio of one pint
(.5 liter) per 125 gallons (473 liters) fuel (or 0.10% by volume).
The microbes live in the fuel-water interface. They need both liquids to survive. These microbes find excellent
growth conditions in the dark, quiet, nonturbulent nature of the fuel tank.
Microbe growth can be eliminated through the use of commercially available biocides. There are two basic
types on the market.
The water soluble-type treats only the tank where it is introduced. Microbe growth can start again if fuel is
transferred from a treated to an untreated tank.
Diesel fuel soluble-type, suds as Biobor manufactured by U.S. Borax or equivalent, treats the fuel itself and
therefore the entire fuel system.
Units going into storage should be treated as follows: Add the biocide according to the manufacturer's
instructions. This operation is most effective when performed as the tank is being filled. Add dry gas in the
If the fuel tanks were previously filled, add the chemicals and stir with a clean rod.
Item 3 Fuel Lines
Make a visual check for fuel leaks at the crossover lines and at the fuel tank suction and return lines. Since fuel
tanks are susceptible to road hazards, leaks in this area may best be detected by checking for accumulation of
fuel under the tanks.
Item 4 Cooling System
Before starting the engine, always check the coolant level. Make sure the coolant covers the radiator tubes.
Add coolant as necessary. Do not overfill.
Make a visual check for cooling system leaks. Check for an accumulation of coolant beneath the vehicle during
periods when the engine is running and when the engine is stopped.
Clean the cooling system annually (vehicle engines) or every 1000 hours (30,000 miles nonvehicle engines)
using a good radiator cleaning compound 2 in accordance with the instructions on the container. After the
cleaning operation, rinse the cooling system thoroughly with fresh water. Then fill the system with soft water,
adding a good grade of rust inhibitor or a high boiling point-type antifreeze (refer to Engine Coolant in Coolant
Specifications). With the use of a proper antifreeze or rust inhibitor, this interval may be lengthened until,
normally, this cleaning is done only in the spring or fall. The length of this interval will, however, depend upon
an inspection for rust or other deposits on the internal walls of the cooling system. When a thorough cleaning of
the cooling system is required, it should be reverse flushed.
Inspect all of the cooling system hoses at least once every 12 months or 20,000 miles (700 hours) to make sure
the clamps are tight and properly seated on the hoses and to check for signs of deterioration. Replace the
hoses if necessary.