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Everything You Need To Know About The Coolant Reservoir

September 7, 2022
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The engine coolant reservoir stores excess coolant fluid until the engine cools down. This is critical in maintaining optimum pressure in the engine’s cooling system. 

If your car’s coolant reservoir is faulty, it’ll fail to combat the rising pressure inside the cooling system, resulting in your engine overheating and other expensive repairs.

But how does the coolant reservoir work in your car’s cooling system? 
And how can you tell if the coolant reservoir is functioning properly? 

Don’t worry! We’ve got you covered.

This article will explore the role of the coolant reservoir in your car. We’ll also discover the signs of a bad engine coolant reservoir, what causes it to overflow, whether you can drive with a bad coolant reservoir replacement, and its replacement cost. 

This Article Contains:

The Role Of The Coolant Reservoir In The Engine’s Cooling System

The coolant reservoir or overflow tank is a translucent plastic tank mounted on the engine bay. It’s responsible for storing the hot coolant fluid until the engine has cooled down. 

But how does this system work? Let’s dig a little deeper.

The engine’s coolant system operates on a closed-loop circuit, meaning nothing can enter or leave the system (unless there’s a leak.)

This system has many components that work together to prevent the engine from overheating. They do this by circulating the coolant through the engine, ensuring it’s well-lubricated and running smoothly. 

Some of these key components are as follows:  

As the coolant circulates through the engine compartment, it absorbs the heat produced by the engine. Eventually, the coolant fluid reaches a boiling point, increasing the pressure within the system. 

The pressure cap relieves this pressure by sending the boiling coolant fluid through the radiator hose and thermostat housing into the coolant reservoir (also known as the expansion tank.)

When you turn off your vehicle, this excess coolant fluid is brought to an acceptable temperature, ready to be recirculated into the engine. 

Coolant reservoirs are made from high quality materials. But their location, function, and design make them susceptible to wear and tear, affecting your vehicle’s performance.

So, how do you identify a bad radiator coolant overflow tank?  

3 Symptoms Of A Bad Coolant Reservoir

Here are some obvious signs of a faulty or damaged coolant overflow tank: 

1. Low Coolant Level

A damaged or faulty engine coolant reservoir could result in your coolant level constantly running low. Depending on the severity of the damage, you’ll notice small or large coolant fluid stains under your vehicle. When the coolant level is low, the ECM (Engine Control Module) will log DTC P2560. 

Note: A coolant leak could also happen due to a damaged reservoir cap, radiator hose (also referred to as coolant hose), or radiator filler neck, resulting in a low coolant level.

2. Coolant Odor

If you’ve noticed a sweet smell (like maple syrup) from the front of your vehicle or throughout the cabin, it could be due to a bad overflow reservoir tank. Typically, this indicates a coolant leak within the engine compartment and must be diagnosed soon.

3. Engine Overheating

Bad coolant reservoirs may fail to store the excess coolant or combat the increased pressure, resulting in the engine overheating. You’ll notice the temperature gauge flickering on your dashboard when this happens. 

Besides these faulty reservoir tank symptoms, you could also have an overflowing coolant tank.    

Let’s look at its potential triggers. 

What Causes The Coolant Reservoir Tank To Overflow?

Here are some reasons why your engine coolant reservoir could be overflowing:

Now, let’s find out if your car is still drivable with a faulty coolant reservoir. 

Can I Drive With A Damaged Coolant Reservoir?

Yes, you can still drive with a damaged coolant reservoir. However, eventually, the cooling system will run out of coolant fluid, resulting in the engine overheating, the engine losing power, or the air conditioning not working.

In some cases, it could damage your engine, radiator, or thermostat, so it’s best to consult a reputable mechanic soon.

Looking to replace a coolant reservoir tank?
Let’s explore the costs.

How Much Does A Coolant Reservoir Tank Replacement Cost?

The cost of a coolant reservoir tank replacement ranges from $300 to $450. Here are the estimated costs for some popular car models:

Final Thoughts

A malfunctioning coolant reservoir could prevent the cars cooling system from performing efficiently, resulting in several engine-related problems or permanent damage. 

And since this system is quite complex, it can be difficult to identify or fix the issue.

That’s where RepairSmith comes in.

RepairSmith is a round-the-clock mobile auto repair and maintenance solution that you can conveniently book online. We offer upfront pricing and a 12-Month, 12,000-Mile warranty on all our repairs. 

So, the next time you require a coolant reservoir maintenance or replacement service, contact RepairSmith, and our technicians will come by to fix the problem.