Cooling System Maintenance and Repair

An engine that is overheating quickly self destruct, so proper maintenance of the cooling system is important to the life of the engine and the trouble-free operation of the cooling system in general.

The most important maintenance item is to flush and refill the coolant periodically. The reason for this important service is that antifreeze has a number of additives that are designed to prevent corrosion in the cooling system. This corrosion tends to accelerate when several different types of metal interact with each other, which causes scale that eventually builds up and begins to clog the thin flat tubes in the radiator and heater core—causing the engine to eventually overheat.

The anti-corrosion chemicals in the antifreeze prevent this, but they have a limited lifespan.

Newer antifreeze formulations will last for 5 years or 150,000 miles before requiring replacement. These are usually red in colour and are referred to as “Extended Life” or “Long Life” antifreeze.

GM has been using this type of coolant in all their vehicles since 1996. The GM product is called “Dex-Cool”.

Most antifreeze used in vehicles, however, is green in colour and should be replaced every two years or 30,000 miles, whichever comes first. You can convert to the new long-life coolant, but only if you completely flush out all of the old antifreeze. If any green coolant is allowed to mix with the red coolant, you must revert to the shorter replacement cycle.

Look for a shop that can reverse-flush the cooling system. This requires special equipment and the removal of the thermostat in order to do the job properly. This type of flush is especially important if the old coolant looks brown or has scale or debris floating around in it.

If you remove the thermostat for a reverse flush, always replace it with a new thermostat of the proper temperature. It is cheap insurance.

The National Automotive Radiator Service Association (NARSA) recommends that motorists have a seven-point preventative cooling system maintenance check at least once every two years. The seven-point program is designed to identify any areas that need attention.

It consists of the following:

  • A visual inspection of all cooling system components, including belts and hoses
  • A radiator pressure cap test to check for the recommended system pressure level
  • A thermostat check for proper opening and closing A pressure test to identify any external leaks to the cooling system parts; including the radiator, water pump, engine coolant passages, radiator and heater hoses, and heater core
  • An internal leak test to check for combustion gas leakage into the cooling system
  • An engine fan test for proper operation A system power flush and refill with car manufacturer’s recommended concentration of coolant

Let’s take these items one at a time.

Visual Inspection

What you are looking for is the condition of the belts and hoses. The radiator hoses and heater hoses are easily inspected just by opening the hood and looking. You want to be sure that the hoses have no cracking or splitting and that there is no bulging or swelling at the ends. If there is any sign of problems, the hose should be replaced with the correct part number for the year, make, and model of the vehicle. Never use a universal hose unless it is an emergency and a proper moulded hose is not available.

Heater hoses are usually straight runs and are not moulded, so a universal hose is fine to use and often is all that is available. Make sure that you use the proper inside diameter for the hose being replaced. For either the radiator hoses or the heater hoses, make sure that you route the replacement hose in the same way that the original hose was running. Position the hose away from any obstruction that can possibly damage it and always use new hose clamps. After you refill the cooling system with coolant, do a pressure test to make sure that there are no leaks.

On most older vehicles, the water pump is driven by a V belt or serpentine belt on the front of the engine that is also responsible for driving the alternator, power steering pump and air conditioner compressor. These types of belts are easy to inspect and replace if they are worn. You are looking for dry cracking on the inside surface of the belt.

On later vehicles, the water pump is often driven by the timing belt. This belt usually has a specific life expectancy at which time it must be replaced to ensure that it does not fail. Since the timing belt is inside the engine and will require partial engine disassembly to inspect, it is very important to replace it at the correct interval. Since the labour to replace this belt can be significant, it is a good idea to replace the water pump at the same time that the belt is replaced. This is because 90 per cent of the labour to replace a water pump has already been done to replace the timing belt. It is simply good insurance to replace the pump while everything is apart.

Radiator pressure cap test

A radiator pressure cap is designed to maintain pressure in the cooling system at a certain maximum pressure. If the cooling system exceeds that pressure, a valve in the cap opens to bleed the excessive pressure into the reserve tank. Once the engine has cooled off, a negative pressure begins to develop in the cooling system. When this happens, a second valve in the cap allows the coolant to be siphoned back into the radiator from the reserve tank. If the cap should fail, the engine can easily overheat. A pressure test of the radiator cap is a quick way to tell if the cap is doing its job. It should be able to hold its rated pressure for two minutes. Since radiator caps are quite inexpensive, I would recommend replacing it every 3 years or 36,000 miles, just for added insurance. Make absolutely sure that you replace it with one that is designed for your vehicle.

A thermostat check for proper opening and closing

This step is only necessary if you are having problems with the cooling system. A thermostat is designed to open at a certain coolant temperature. To test a thermostat while it is still in the engine, start the engine and let it come to normal operating temperature (do not let it overheat). If it takes an unusually long time for the engine to warm up or for the heater to begin delivering hot air, the thermostat may be stuck in the open position. If the engine does warm up, shut it off and look for the two radiator hoses. These are the two large hoses that go from the engine to the radiator. Feel them carefully (they could be very hot). If one hose is hot and the other is cold, the thermostat may be stuck closed.

If you are having problems and suspect the thermostat, remove it and place it in a pot of water. Bring the water to a boil and watch the thermostat. You should see it open when the water reaches a boil. Most thermostats open at about 195 degrees Fahrenheit. An oven thermometer in the water should confirm that the thermostat is working properly.

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