Car Cooling System Problems? 8 Common Issues & Fixes

Your car’s cooling system is one of the major areas that can have problems. Overheating, overcooling, and leaks are just a few of the issues you may find over the life of a car.

If you’re currently having issues with your cooling system, these common issues and fixes may help you diagnose and repair your car instead of taking it to a professional mechanic to do the work.

#1 – You Find A Leak from Somewhere

Leaks are the problematic issues with cooling systems as there are multiple components in the system and they all have connections.

The coolant inside the cooling system must flow from the engine, through the heater core, and back to the radiator to keep all components at the appropriate temperature.

These are the four major components of the cooling system:

  • Radiator – The radiator is made from tanks on the side of the radiator and tubes that carry coolant between the tanks. The main hoses connect to a port on each side that allows the coolant to flow in and out of the radiator.
  • Water pump – The water pump uses power from a belt or an electrical connection to turn a vane inside the housing. That vane circulates the coolant throughout the entire cooling system.
  • Heater Core – The heater core is a smaller radiator that distributes heat inside the cabin of the vehicle. The hot coolant transfers heat to the heater core and it disperses (or radiates) the heat with support of a fan in the dash.
  • Heater / coolant hoses – the hoses transport coolant between the major components in the cooling system. Each hose’s connection will have a clamp to secure a connection from the hose to the component.

How to Fix It

The first step in fixing a cooling system leak is determining why it is occurring.

You may have a major component that is leaking, such as a cracked radiator. It could also be as simple as a connection between a hose and a component needs to be tightened.

Once you know why the leak is occurring, replace the part in question or tighten the connection to stop the leak.

If you can’t easily find a leak, try using an ultraviolet dye that can be added to the cooling system. You can use a black light to search the cooling system to quickly find the source of the leak.

#2 – Your Car is Overheating

Overheating isn’t just a problem for those hot summer months. It can happen under any weather conditions, come rain or shine.

Overheating occurs because you’re low on coolant, your radiator is blocked and keeping air from flowing through it, or something is stopping the coolant from flowing in the cooling system.

How to Fix It

If your car is running hotter than normal, the first thing to do is turn it off and allow it to cool completely. You shouldn’t diagnose why it’s overheating while it’s hot.

Once it’s cool, remove the radiator cap or check the coolant overflow bottle to see if there is coolant in the system. If it is low, you can refill the system to the correct amount. If a leak suddenly appears, you know why the system is low on coolant and can then repair the leak.

Next, you can check if the radiator is blocked and not allowing air to pass through the cooling veins. Dirt, leaves, and debris can build on the front of the radiator and A/C evaporator enough to prevent proper cooling.

If you find blockage, remove and clean the radiator and evaporator.

The last suggestion is to run the engine with a full cooling system and the radiator cap off. The engine running will circulate the coolant in the system, and you should see it moving when you look inside the radiator (where the cap connects to).

If you can’t see coolant moving or flowing in the radiator, you most likely have a blockage in the system that needs to be removed.

If you’re finding this a little complicated, head over to our article, Car Overheating? 11 Most-Common Reasons (For Beginners)

#3 – Your Car Is Overcooling

You may think that your car running cooler or at a lower temperature than it’s supposed to would be a good thing, but it’s not always the case.

Overcooling happens when something in the cooling system is out of balance. The most likely cause of the improper balance is the thermostat has stuck open and isn’t controlling the flow of the coolant.

Its job is to open and close to keep the cooling system at the correct operating temperature (somewhere between 180° – 220°F) by controlling the flow of the coolant in the system.

If it’s stuck open, the coolant doesn’t absorb enough heat from the engine to reach the correct operating temperature.

How to Fix It

If the problem is indeed the thermostat being stuck open, it should be replaced. Once it has been replaced, check for any additional leaks, and refill the cooling system with new coolant.

You can test if the thermostat opens or closes by placing it in a boiling pot of water. It should be closed before it is in the hot water, and it should open after a few seconds in the hot water.

Overcooling can reduce engine power, increase cylinder wear, reduce fuel economy, and increase your engine oil friction.

#4 – Your Cooling Fan Is Broken Or Not Working Correctly

Your car’s cooling fan is either mechanical or electrical, and the sole purpose is to assist the cooling system by rejecting heat. If it’s broken or underperforming, your car should show signs of overheating.

A mechanical cooling fan will be driven by a belt turning around a pulley. It is generally attached to the water pump, and it should have a clutch that engages the fan when the car reaches operating temperature.

An electric cooling fan will turn on at a certain temperature or when another component is turned on to prevent overheating. Most air conditioning systems will turn on the cooling fan to assist in removing heat from the air condition evaporator.

How to Fix It

A mechanical cooling fan may have a broken belt that isn’t turning the pulley, the clutch may be worn out and not engaging correctly, or the fan itself could be damaged.

Determine if any of these are the case and replace the broken part.

If you have an electrical fan, the circuit may not be receiving power due to a blown fuse, damaged wiring, or the fan is damaged.

#5 – Your Water Pump Is Worn Out

Your water pump circulates coolant inside the cooling system. As it ages, it may develop noises indicating a bearing has gone bad, a pulley has come loose, or the impeller inside the pump has stopped spinning correctly.

It can also develop a leak from one of the sealed surfaces to the engine block or a coolant hose. A leak or the pump failing to circulate coolant will contribute to overheating.

How to Fix It

The water pump is designed to be replaced, so if it fails, it’s time to remove it and replace it.

#6 – Your Radiator Cap Has Worn Out

Your radiator cap contains a spring that keeps pressure on the opening to prevent the coolant from coming out. This spring will fatigue over time, and it will allow the coolant to flow to the overflow bottle. Here’s a guide to understand what the radiator does in a car.

This leads to low coolant in the cooling system and eventual overheating.

How to Fix It

Replace the radiator cap and refill the cooling system to the proper amount.

Radiator caps generally wear out in 5 to 7 years of use. They are economical to replace.

#7 – Your Engine Has A Blown Head Gasket

There is a gasket between the cylinder head and the engine block that is meant to prevent oil and coolant from mixing in the combustion cylinder. A damaged head gasket will allow coolant and oil to mix.

You may find these symptoms with a damaged (aka blown) head gasket:

  • White-colored smoke or steam from the car’s exhaust indicates coolant is being burned in the combustion chamber.
  • The engine oil has a frothy or bubbly texture rather than a smooth texture.
  • The coolant in the radiator shows a brown milky-colored mixture with oil in the cooling system.

How to Fix It

Replacing a head gasket is a large job, even for a professional mechanic.

The cooling system must be drained, the intake and exhaust manifolds must be removed, and the fuel system connection at the engine may need to be disconnected at a minimum.

If you’re not confident in all steps of the replacement, it’s a job that should be taken to a professional to diagnose and repair.

#8 – You Are Overworking Your Cooling System

This last issue is more about you than the cooling system. Drivers can overwork their cooling systems to the point of component failure or damage to another system on the car.

A truck pulling too heavy of a trailer can heat the transmission fluid beyond normal operating temperature and then transmit that extra heat to the radiator, causing overheating.

How to Fix It

Overworking the cooling system is common, but there are simple ways to prevent it: add extra support/capacity or don’t do it.

The aftermarket has additional coolers that can be safely added for additional cooling capacity or the radiator can be replaced with a larger one for extra cooling capacity.

Otherwise, drive your vehicle within the manufacturer’s recommendations.

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