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Cooling-System Basics

Originally Published in MotorHome Magazine

The traveling bone that all RVers are born with begins to ache with anticipation as the summer travel season arrives. Summer travel means much higher temperatures and greater demands on your motorhome’s powertrain. Before you hit the road, make sure you understand your coach’s cooling system and its requirements to ensure reliable service, not to mention to prevent unexpected problems on the road.

Spring is a time when insects are at or near their peak numbers. Insects can clog the cooling fins of radiators, causing overheating. To prevent this, use a garden hose to flush dead bugs out of the fins from the fan side forward. Then install a bug screen made from fiberglass window screen in front of the radiator. Attach the corners with thin wire tied to hold the screen in place.

Driving with an overheated engine can destroy an engine in minutes. Here are some things you can do to avoid problems and keep your RV engine cool:

  • Install a new thermostat and pressure cap.
  • Have the cooling system flushed and refilled with a 50/50 mixture of antifreeze and distilled water.
  • Have the system pressure tested.
  • If hoses and belts are more than about four years old, replace them.
  • Have the fan clutch tested.
  • Gasoline engines will ping under load more in hot weather. If it does, reduce throttle until the sound goes away to prevent damage. Change to a higher-octane gasoline as soon as possible.
  • As a temporary solution, if an engine is running too hot, shut off the dash air conditioner and run the heater at full blast. (This only works if the engine still has coolant, but is running hot due to insufficient capacity. Do not try this if the coolant is leaking out.)
  • Never run the engine if the temperature gauge is in the red zone.


*Note: Owners of Cummins-powered diesel coaches should note that the Cummins engine operator’s manual requires the SCA level of coolant in the cooling system to be checked every six months to ensure the correct level of anti-corrosive additives are present. This is to prevent damage to cooling system components by either too low or too high a level. Cummins maintenance schedules require that the entire cooling system be flushed and changed at 24 months. Failure to do so may void warranty coverage.

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