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Having low coolant is bad for your engine. Not enough coolant means all the heat your engine generates can’t be removed—too much heat results in excessive engine wear.

Here we’ll look at all the signs of low coolant. Some only occur in certain situations – for instance, when accelerating or at idle.

There are ten in total which we’ll go into detail about below.

Signs Of Low Coolant

1. The Cabin Heater Doesn’t Work.

Has your car’s cabin heating system stopped working efficiently? Your engine’s coolant system is connected to the heater core. If the level is low, the heater core may not get all the heat – within the coolant – blown into the cabin via a fan. If there is a leak, air bubbles can also enter the system and stop the flow of coolant within the system.

2. Engine Overheating and Refuses To Restart

This can be due to several reasons–a bad thermostat, for example- but it’s also possible that you need some antifreeze. Check the coolant level if you haven’t done so in a while. Your car’s ECU – won’t allow your car to start if a sensor indicates that your car is overheating as doing so could cause damage to the engine.

3. Engine Shuts Down While Driving In Normal Conditions

The ECU will stop your car if it recognizes that damage is likely. However, you will almost certainly get an engine warning light on the dashboard before the car gets to this stage.

4. Engine Overheats When Driving Uphill

Usually, you’ll be in a lower gear, and the engine will work harder. A harder-working engine requires more cooling. The heat won’t be taken away well enough if there isn’t enough coolant in the system.

5. Steam Coming From The Engine

The radiator filler cap also works as a pressure release valve. If the coolant’s pressure rises and the water gets too hot, steam will be released through the radiator cap to depressurize the system. This can lower the coolant level.

Steam could also be caused by a leak in a hose or the radiator.

5. Clicking or Knocking Sound Coming From The Engine

If your coolant is low, it won’t take away the heat from the engine. The oil temperature can increase, pistons and valves may start to fail, and the head gasket may blow. These low coolant noises are a red warning light flashing brightly.

You need to stop the engine and not turn it on again. Major damage may have already been done- starting the car again will make it worse. 

6. White Smoke From The Exhaust

Some other signs to look for if you think your car might be low on coolant are white smoke coming from the exhaust pipe. This is a bad sign and indicates that coolant is mixed with the oil and fuel in your car’s engine. They should never meet. The coolant is then expelled with combustion gases through the exhaust – giving a white appearance.

7. Poor Fuel Economy

Low coolant can lead to increased fuel consumption due to overheating the engine. When an engine works inefficiently, it will need to burn more fuel per mile to do the same job as an efficient engine.

8. Engine Warning Light

An engine warning light may also signify a whole host of engine problems. The ECU has detected a problem and is letting you know. This could be low coolant if seen with other indicators in this article.

In some cars, the light can flash when the ECU detects a more serious problem. The ECU may also be in Limp – or get me home – mode, where the car operates on reduced power to reduce the risk of damaging the engine.

8. Low Coolant Light Is On

A sure sign you have a leak or the coolant level is low. The sign is red and looks like a thermometer in water.

9. A Sweet Smell Coming From The Exhaust 

Do you notice a sweet or fruity smell coming from the tailpipe? This is due to coolant/antifreeze leaking and leaving your exhaust system with combustion gases. This is a bad sign and indicates a blown head gasket.

10. Temperature Gauge In The Red

Cars’ coolant temperature varies depending on whether the car has just been started, the outside temperature, and whether you are driving slowly or in a line of traffic. 

The temperature gauge will go up and down to reflect this. However, if it is now higher than you would normally see, ie. Outside of its normal temperature range then, this indicates that low coolant could be the issue.

Many visitors also read this article: Why Does My Car Keep Overheating? 12 Reasons and Fixes

Is It OK To Drive With Low Coolant?

No. If you notice your car is low on coolant, STOP DRIVING IMMEDIATELY! You risk damaging the engine, water pump, and coolant system.

What Are The Reasons For The Low Coolant Level?

It’s essential to check the common causes of overheating in your vehicle so you can address the issue before it damages your engine. Here are five common reasons why your car may be overheating:

  • Your car may be overheating due to a faulty thermostat.
  • Water pump failure causes air bubbles to flow into the cooling system, preventing coolant circulation through your engine.
  • Coolant hose leaks and faulty radiator cap seal.
  • Leaking head gasket and cracked or warped cylinder head may cause coolant to leak into the cylinders, burning them up.
  • Loose fan belt, stuck water pump pulley, and faulty radiator fan contribute to overheating issues.

Can I Add Coolant To My Car Myself?

Sure. First, locate the engine coolant reservoir and open it. If the coolant level is low, add enough coolant to the reservoir (not the radiator). Diluted coolant can be used alone or combined with a 50/50 mixture of concentrated coolant and distilled water.

You usually don’t have to add coolant very often, but you should check the coolant level regularly and test the concentration at least twice a year or every 12000 miles.

However, if the engine has overheated, you must be extremely careful when refilling the coolant.

Adding straight water to the reservoir may cause the formation of air bubbles, which cannot be compressed as well as water. It’s okay in an emergency, though, if you don’t have coolant.

What Are The Effects of Low Coolant On Your Car?

Driving with an overheated car can damage both your engine and other car parts, e.g., cylinders and pistons, valves, spark plugs, etc.

What Can The Cost Be of Not Addressing A Low Coolant Problem?

The repair cost of overheating depends on how severe the damage is to your engine. Major engine problems may run in the thousands. This is why it’s essential to find out what’s causing your vehicle to overheat before it gets any worse.

Many visitors also read this article: Bad Alternator Cause A Car To Run Hot and Overheat? [ANSWERED]

Can I Use Water Instead of Coolant In My Car?

Water is corrosive when in long-term contact with metals such as aluminum, copper, and steel. It may cause damage to the radiator and other parts of a vehicle’s cooling system.

Coolant is better than water because it has a low freezing temperature. One of the main purposes of coolant is to prevent the engine from freezing. 

Water is not as good as a coolant because it does not effectively reduce the temperature in the engine bay as a coolant does. In addition, water, on its own, can’t do the job of antifreeze since it has a lower boiling and freezing point range and can’t protect your car’s engine.

However, in the case of an urgent situation, you may use water instead of coolant.

How To Choose The Right Coolant For Your Car

There are numerous coolants, but the essential components are ethylene or propylene glycol and water.

You’ll need to refer to a compatibility chart or your handbook to choose the right coolant for your car.

Different cars use different coolants, and they are not interchangeable. You can locate a compatible chart online or at a local auto parts store.

Remember, only use the recommended type of coolant for your vehicle. Using another type may cause damage.

However, there are three kinds of coolant which are used for cars, they are:

  • Propylene Glycol 

Most commonly used in newer vehicles. Also referred to as “PG,” this is the same kind of coolant that you put in your refrigerator. It has a very low freezing point, making it great for harsh winter climates. PG also has corrosion inhibitors, meaning it does not need an extra anti-rust additive.

  • Ethylene Glycol  

Ethylene Glycol is not as standard as PG (although it is still used in some newer vehicles), but it has a slightly higher freezing point and contains rust inhibitors. This coolant can be identified by the orange or red color of the liquid inside your radiator.

  • Hybrid Organic Acid Technology or HOAT 

This coolant combines PG and ethylene glycol. It has the corrosion inhibitors that ethylene glycol provides and has some lower freezing point properties and freeze point depressants designed to prevent coolant freezing up at sub-zero temperatures.

This is the same coolant used in semi-trucks and other commercial vehicles.

Does Coolant Go Bad?

Coolant does lose its effectiveness over time. 

A tune-up at a car shop should check the mixture when you take your car in, flush it through, and replace it where necessary. 

A low coolant concentration may make your car shake but won’t damage your engine itself, but its additives start to separate, making it less effective at boiling and freezing temperatures.

You can check the concentration yourself with a Coolant tester. It takes a sample from your reservoir and tells you whether the concentration is at an adequate level or needs replacing.

In Conclusion

There are a number of signs pointing to a damaged coolant circuit that will develop before your engine overheats or dies.

  • Heater not working
  • Car shuts down
  • A sweet smell from the exhaust
  • Poor fuel economy
  • The car won’t start

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