Leaks – Oil, Fuel, or Coolant

Although leaks are a common cause of generator start-failure, they are also easily prevented with a little routine maintenance.

Coolant Leaks

Coolant leaks in the block heater hoses account for the most frequent leakage service call. Extreme temperatures in the outlet create harsh conditions for block heaters hoses, and for this reason, rubber hoses should never be used. Silicon hoses are specifically designed for use with block heaters. Isolation ball valves should always be installed for block heater hose connections. Replacing hoses and coolant every three years is recommended, even with generators that use the newer extended-life coolant. Cooling system anti-freeze protection and conditioner should be maintained to the manufacturer's specifications. Periodically, a coolant sample should be sent out for analysis.

Fuel Leaks

When it comes to fuel leaks, the most frequent service calls are due to overfilling of the base tank. This can be caused either by human error or failure of a pump system. Check remote tank pump systems and emergency shut-off systems periodically for proper functioning. Flexible fuel lines should also be checked regularly for cracks and signs of aging.

Oil Leaks

With oil, most leaks are not leaks at all, but rather the result of "wet stacking" (or "engine slobber") caused by excessive no-load run-time. Diesel engine generators are designed to operate with a load; most effectively in the 70-80% range of rated output. When generators operate considerably below the rated output level, at approximately 30%, the engine can start to "wet stack" or "slobber" and affect the performance of the engine. Wet stacking - an accumulation of carbon particles, unburned fuel, lube oil, condensed water and acids in the exhaust system – is caused by low temperature in the combustion chamber. Diesel generators used for commercial purposes undergo load applications that continuously vary between efficient and low output conditions. In these applications, the generator is often paired with an automatic load bank, which will place a false load on the generator system; keeping the engine properly loaded and preventing a wet stack condition.

It is important that your generator be properly sized and designed for your needs. It is recommended that at least 30% of the nameplate rating should be applied to a generator during routine testing. If it is necessary to test with no load, keep run time to a minimum.

Wet Stack Maintenance

If your diesel engine wet stacks, you can clean it up by loading the unit for a few hours to burn off the excess fuel/oil in the exhaust system.

Other Leaks

Another cause of oil leak complaints is directly related to the crankcase breathers. Most engine crankcase breathers vent directly under the engine. The fumes that come out of the breather contain an oil mist. This mist can produce a puddle under the engine and coat the generator and radiator with an oil film that collects dirt and debris. Re-circulating breathers are available to separate the oil and return it to the engine; the remaining fumes are returned to the engine air intakes.