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A vehicle’s engine’s internal combustion component produces a significant amount of heat during the combustion process, with temperatures, at times, reaching well over 200 degrees. Therefore, it is imperative to control this heat by using a cooling system.

A car’s coolant system is a sealed system so that the coolant should, in theory, stay at an even level if everything is working as it should. However, as we all know very well, cars are known for being problematic, and problems leading to insufficient coolant are no exception.

You may now be wondering is it safe to drive with a low engine coolant level, what causes it, and how to know if coolant is low without opening the hood?

This article will provide you with all the relevant information on low engine coolant, answering all you need to know on the matter.

Table of Contents

Most Common Causes of Low Engine Coolant Level

First, before looking at the symptoms, let’s discuss the common causes of low engine coolant levels. Here are the 5 most common causes:

  1. External coolant leaks
  2. Faulty head gasket
  3. Faulty intake manifold gasket
  4. Faulty radiator cap
  5. Faulty EGR cooler

Let’s look at each in more detail!

External Coolant Leak

More than likely the most common cause of low engine coolant levels is external leaks. External coolant leaks can come from anywhere in the coolant system. The good thing about this cause is that external coolant leaks are often visible, allowing you to easily determine where the leak is coming from and hopefully fix it.

Some of the most common places external leaks will come from are the water pump, radiator or around the coolant system’s thermostat.

Faulty Head Gasket

A faulty head gasket, whether that has deteriorated or blown, is another thing that can cause your low engine coolant. The head gasket is designed for separating the compression, oil, and coolant system.

Therefore, a faulty head gasket may cause the coolant to mix with the compression, which will cause the engine to combust the engine coolant. This will be easily recognized by the white smoke pouring from the exhaust pipe.

Faulty Intake Manifold Gasket

Many intake manifolds will cool the air coming through the intake with coolant, and therefore they will have coolant channels inside them. Therefore, you will find a head gasket installed between the intake manifold and the cylinder head.

This intake manifold gasket can start to leak, and it will cause the engine to suck in and combust the coolant. Again, you will be able to recognize this by seeing white smoke from the exhaust pipe.

Faulty Radiator Cap

A faulty radiator cap is another possibility for what is causing your engine coolant to be lower than it should. Inside the radiator cap, you will find an overpressure valve which is due to open if the pressure rises above a specific pressure.

If this valve is faulty, it may happen to open before reaching the correct pressure, and this will therefore cause the coolant to begin leaking out.

Faulty EGR Cooler

One final thing that can cause low engine coolant is a crack inside the EGR cooler. Though, not all car engines have EGR coolers, so you must research if your engine even has one. They are mostly found in European cars.

A faulty EGR cooler with a crack will cause the coolant to leak into the exhaust pipe, which will typically lead to white smoke exiting the exhaust pipe.

Symptoms of Low Engine Coolant

Now, let’s look at the symptoms of low engine coolant which you can look out for to ensure you keep on top of your engine coolant and ensure it’s not low for too long. The easiest way to quickly check if the engine coolant level is low is, of course, by opening the hood and checking the level in the coolant reservoir.

There are, however, some other symptoms you can look out for. Here are the 5 most common symptoms of low engine coolant:

  1. Low Engine Coolant Symbol
  2. Rising temperature gauge
  3. Fluctuating temperature gauge
  4. Faulty Heater
  5. Anti-freeze smell

1. Low Engine Coolant Symbol

The majority of modern-day vehicles have a warning light that will appear on the dashboard if the engine coolant is low. This is an easy indication that your vehicle has low engine coolant, however, not all models have this light, especially if the vehicle model is old.

If the low engine coolant system lights up on the dashboard, it is time for you to check the coolant level to ensure it is sufficient or diagnose why it is insufficient.

2. Rising Temperature Gauge

When the engine is being cooled as it is designed to, the dashboard’s temperature gauge should be below the halfway mark. If the temperature rises over the engine’s working temperature, then there is certainly a problem that will need instant attention.

If your temperature gauge is indicating that the engine’s temperature is higher than the normal working temperature (90 degrees Celsius or 200 Fahrenheit), you will need to shut off the engine to not risk overheating.

3. Fluctuating Temperature Gauge

Another possibility for a low engine coolant symptom you will be able to notice is that the engine temperature gauge may start to fluctuate fast between varying temperatures.

This will occur when the engine coolant is so low that air is pumped around within the coolant system. When an airlock is surrounding the coolant sensor, the temperature will drop, and when the coolant comes again, it will go back to its normal temperature.

4. Faulty Heater

The car’s heater uses the same coolant that runs through the engine. Valves are used to control the car’s coolant inflow; hence, regulating the temperature.

If your heater is not working as expected, you could suffer from low engine coolant because of airlocks in the heater core.

5. Anti-Freeze Smell

Anti-freeze is a compound which is included with the coolant system’s fluid to help prevent the radiator’s water from solidifying during cold winter months.

One distinguishing characteristic of the anti-freeze is that it has a very noticeable sweet smell. If you notice that your engine produces a sweet anti-freeze smell, then the cooling system is likely leaking.

Is It Safe to Drive With a Low Engine Coolant Level?

No, it is certainly not safe to drive with a low engine coolant level. Low engine coolant can cause airlocks in the coolant system and lead to an overheating engine which can destroy expensive parts like the engine block or cause it to seize completely.

Given that refilling the engine coolant is such an easy task, along with considering the consequences of not refilling it, which will follow, you should have no hesitation to refill the coolant when necessary. Just be careful to never open the coolant reservoir when the engine coolant is at a hot temperature.

Consequences of Driving with Low Engine Coolant Level

Finally, let’s discuss the consequences of driving with low engine coolant, which will hopefully be enough to ensure you keep on top of your engine coolant level. Here are some common consequences of driving with a low engine coolant level:

  • Air in the coolant system
  • Overheating engine
  • Blown head gasket
  • Damaged engine block
  • Seized engine

Air in the Coolant System

The first possible consequence that could occur if you drive around with low engine coolant is that the water pump will pump air into the coolant system, ultimately causing airlocks in the coolant system.

As you already know, airlocks will cause the cooling system’s flow to get disturbed, causing an engine to fluctuate temperature and overheat.

Overheating Engine

Generally, because of the airlocks in the coolant system, the water pump will not pump around the coolant to hold the engine at a good temperature, and it will cause the engine to overheat.

An overheating engine will cause many expensive issues with your engine, which we’ll now discuss!

Blown Head Gasket

First up with the engine-related issues is a blown head gasket. This is a very common possibility if you have low engine coolant. Replacing the head gasket is often quite an expensive job, and you can expect repair costs of easily over £500.

Damaged Engine Block

An even more severe issue that can occur if you drive with a low engine coolant is a damaged or cracked engine block. Low engine coolant levels can create hotspots in the cooling system, and these hotspots can cause extreme temperatures in the engine block.

The extreme temperatures may even cause the engine block to crack, and a crack in the engine block or cylinder head is certainly one of the last things you will want to experience. To repair a cracked engine block, you must replace the whole engine block which will be very expensive.

Seized Engine

Most engine parts are typically made of metal, and as you will already know, metal expands and shrinks depending on its temperature. If the engine is not holding the temperature properly due to low coolant, it is possible for the engine parts to expand so much that significant damage will occur, leading to engine seizure.

The big problem here is that the only way to fix a seized engine is to tear the whole engine apart to locate the issue before repairing it which will be very costly.

FAQs (Frequently Asked Questions)

What happens if the coolant is low?

If your car engine coolant is low, it could potentially lead to air being in the coolant system which would ultimately lead to overheating. If your car engine overheats, it’s possible the blown head gasket, damaged head block, or even a completely seized engine.

How do I know when my coolant is low?

It is important to check the coolant level when the engine is not hot to avoid any potential injuries from escaping steam or hot coolant. Open your vehicle’s hood and locate the coolant reservoir. Observe the coolant level by looking at the side of the reservoir. The coolant should be between the minimum and maximum marks. If the coolant level is below the minimum mark or significantly lower than it should be, it is an indication that your coolant level is low.

Can I drive with slightly low coolant?

While driving with slightly low coolant levels for a short distance may be possible in some cases, it is not recommended for an extended period or under challenging conditions. It is always best to top up the coolant to the appropriate level or have the vehicle inspected by a qualified mechanic to identify and repair any cooling system issues promptly.