A How-To Guide for Cooling System Maintenance

Posted by Jason Unrau on

Everyone has seen the poor guy sitting on the side of the road with his hood up. Steam is billowing from under the hood and you can tell from his body language that it hasn’t been a good day, and it’s not getting better anytime soon.

A cloud of white steam puffing out from the engine bay is just one sign that a cooling system is in disrepair. Like any vehicle system, it required maintenance and repairs to keep it working as it should.

Here’s what a cooling system is designed to do, how it works, why it’s important, and how to properly maintain your cooling system.

What a Cooling System is Meant to Do

An engine has an optimal operating temperature range. Between 195 and 220 degrees Fahrenheit is where an engine runs most efficiently. When an engine stays in this range, it reduces the amount of harmful NOx emissions that are produced in the combustion chamber. At the same time, it prevents the engine oil from breaking down so that it can continue to protect your engine.

A cooling system is designed to keep an engine operating in that prime zone. Anything less and your catalytic converter will have to pick up the slack in burning off unburned particles from the combustion process. Anything higher and you’ll be spewing noxious gases into the atmosphere anyway.

How an Engine Cooling System Works

A cooling system works on a basic heat exchanger circulation system. A blend of water and concentrated antifreeze, typically ethylene glycol, fills the system.

  • The water pump pulls coolant from the engine and into the radiator.
  • Air is drawn through the radiator with either an electric cooling fan or mechanical fan clutch where heat in the coolant transfers into the air to dissipate into the atmosphere.
  • The cooled coolant flows through the engine block, cylinder heads, and even the throttle body and turbocharger at times where heat is transferred from the hot metal into the less dense coolant.
  • Coolant then diverts through the heater core inside the car where some heat is dispersed, if it’s requested.
  • The cooled fluid then goes back to the water pump to start the circuit all over.

At the engine, a thermostat prevents coolant from flowing freely into the engine until it’s warmed up to operating temperature. It’s only at that point that the thermostat opens and coolant flows through.

What Happens if the Cooling System Isn’t Working?

The biggest issue with a cooling system is when it gets too hot, and that’s when you get breakdowns occurring. Potential issues associated with overheating include hot coolant boiling out of the overflow bottle, a warped cylinder head from overheating, and even a seized engine due to excessive heat.

Enemy Number One of an engine is heat. That’s why a cooling system is so important.

Common Cooling System Failures

There are various forms of cooling system issues that you need to be aware of. If you properly maintain and service your cooling system, you’ll avoid having to deal with most or all of these concerns.

  • A collapsed radiator hose. The hoses from the radiator to the engine are made of synthetic and natural rubber with cotton and Kevlar strands woven into the core. Radiator hoses can deteriorate and collapse, restricting coolant flow. Or, they can spring a leak.
  • A punctured radiator. More often than not, a leaking radiator is due to a stone that impacted the rad through the grille. A radiator can also leak from a seam or the draincock at the bottom.
  • A faulty water pump. If the fins on the water pump corrode or break, it might not circulate enough coolant to prevent overheating.
  • A failed thermostat. While a thermostat is a small-ticket item, it can cause big problems if it sticks closed – or open, for that matter.
  • A leaking heater core. The part that heats your car’s interior can develop a leak too. When that happens, coolant usually leaks onto the passenger floor of your car.
  • Blocked radiator. Aging coolant reacts with the metal in your engine and causes it to be acidic. Deposits can form inside your radiator, blocking coolant from circulating throughout.
  • Broken or loose serpentine belt. The belt that spins the water pump in some cars may be loose or worn, preventing it from turning the water pump effectively.

How to Perform Cooling System Maintenance

Engine coolant has an average lifespan of five years or 100,000 miles. Some cars may be more or less, and the service interval is found in your owner’s manual maintenance schedule. If you need to replace any cooling system components, you should drain and fill the system with new fluid.  Here’s what you need to do to perform cooling system maintenance.

Change the Engine Coolant

When it’s time to change the engine coolant, here are the steps.

  • Wear gloves and eye protection as engine coolant may be HOT!
  • Run the engine until it’s at operating temperature. You need the thermostat to open for the cooling system to fully drain. Then turn the engine off.
  • Place a catch basin under the radiator drain plug. Cautiously open the radiator cap, then open the drain plug. If your radiator doesn’t have a drain plug, remove the lower radiator hose at one end to drain.
  • Let it completely empty, then put the radiator hose back on.
  • Fill the system with a 50-50 blend of concentrated engine coolant and water, then bring up to operating temperature to get any air out of the system.

Flush the Engine

If you can see greenish-blue crusty deposits in the radiator already, or if there are floaty bits in the coolant, it’s best to do an engine flush.

  • Prior to warming the engine to operating temperature, add radiator flush additive to the coolant.
  • Run the engine as long as it says to on the bottle.
  • Drain the cooling system as directed, then flush the cooling system with clean water to remove any debris or deposits.
  • Fill the cooling system as usual.

Check the Cooling System Hoses

Part of your cooling system maintenance should be checking your cooling system hoses. That includes radiator hoses as well as heater core hoses. Squeeze the hose in several places, looking for it to spring back into its normal round shape quickly. If it doesn’t, replace the hose – it’s ready to collapse or burst.


Whatever car model you drive, regardless of year or trim level, AfterOEM has all the parts you need to maintain or repair your cooling system. Browse our listings to find parts specific to your year, make, and model.