Newer vehicles use long-life radiator coolant that is specially formulated to last up to 150,000 miles or five years in-between changes. You still need to check the system as neglecting the cooling system is not a good idea. According to the US Department of Transportation, the leading cause of mechanical breakdowns on the highway is attributed to cooling system failure.
NOTE: If you have an older vehicle that used conventional antifreeze in the cooling system, be aware that this fluid needs to be changed every two years or 30,000 miles instead of the new five-year standard. This replaces the corrosion inhibitors that get depleted.
By checking the coolant level, including the strength and condition on a regular basis, you will know early if there is a problem. This will also help to minimize the risk of overheating and the many other possible problems caused by worn-out or diluted coolant.
Regardless of how new or old the coolant is, leaks can happen any time. Usually but not always, if the coolant is low, the system has a leak. The hoses, gaskets and seals are particularly bad for leakage as they age. The radiator and heater core have similar problems. Any leak needs to be found and fixed as soon as possible.
Just because your coolant light comes on, that doesn't mean you have a leak. There can be many possibilities. The first thing to do would be to check if your coolant is actually low.
Checking your coolant levels
As radiators and hot coolant can cause burns, be careful when attempting to do any work on them.
- Allow the radiator to cool first.
- Cover the radiator cap with a heavy cloth material.
- Stand as far back as you can when removing the cap. If the radiator cap does not have a pressure-relief lever, tighten the cap and then loosen it a half turn to the first notch. If it is equipped with a pressure-relief lever, lift the lever into the open position.
- Not all pressure may have escaped and the cap gasket could still be stuck.
- Once the cap has been removed, coolant can erupt.
- Check the hoses for leaks.
- Tighten the hose clamps.
- Replace the hoses if required.
- Drain the radiator fluid in an appropriate container if the radiator has to be removed for repair.
- Dispose of the radiator fluid in accordance with local environmental agency requirements.
If the level is low, then go on to visually inspect all hoses, clamps, seals and areas where drips might have gone onto, including the overflow tank.
If there are still no signs of a leak, as noted by moisture, wet spots, suspicious stains, then you can possibly assume that there is no leak. It's not a guarantee as the leak could be going into the engine block for instance. The only way to know is to check the engine oil for color and quantity. If the oil is white to grey then it is possible that the coolant is leaking in.
Other possible causes of low coolant alarm but no apparent leaks can be simple things:
- A bad radiator cap can which allows the coolant to escape
- A bad sensor can give incorrect readings and causes the warning light on the dash to come on
- A blocked radiator can cause problems in the flow of the coolant, which could also cause the sensor to give an incorrect reading and force the light to turn on.
- Air bubbles can be difficult to get out even if the system has a bleeder valve for getting the air out. Without bleeder valves, it is even more difficult.
If a visual inspection of the cooling system reveals no external coolant leaks and the light continues to be lit, regardless of the level, you should take the vehicle in and get it checked. Either there is a problem with the sensor or the system. Either way, you don't want to have the problem persist. If the coolant level isn't completely full with coolant then the engine can overheat and boil over.