What causes the Coolant Reservoir to Crack and How to Fix It?

The cooling system is an essential part of your car that helps keep the engine at normal operating temperature—preventing it from overheating. The system does this by circulating coolant to the engine to absorb heat. The reservoir is an essential part of the cooling system that houses reserved coolant. If it cracks, it’ll cause lots of problems.

Age and wear, overheating, too much pressure buildup, poor maintenance, and expansion and contraction are the primary causes of a cracked coolant reservoir. The repair is usually simple. In most cases, you can fix it by applying epoxy resin or a sealant on the cracked surface. But if the reservoir is severely damaged or the crack is large, the best fix is to replace it.

coolant reservoir cracked

Symptoms of a Cracked Coolant Reservoir

Low coolant levels, coolant odor, engine overheating, and fluctuating temperature readings are some of the most apparent symptoms of a cracked coolant reservoir. Inspect the coolant reservoir for cracks once you notice any of these signs.

Low coolant

A cracked or damaged coolant reservoir will cause leaks, which will cause the cooling system to constantly run low on coolant. Depending on the severity of the cracks, you will see small or large coolant puddles underneath your car. When the coolant level is low, the PCM/ECU will log error code P2560.

However, kindly note that coolant leaks can occur from other parts of the cooling systems. Those include the radiator, radiator hose, radiator cap, thermostat, or water pump. Hence, do not point accusing fingers at the reservoir because you have leaks until you determine where the coolant is leaking from.

Coolant smell

Another obvious coolant reservoir cracked symptoms is a sweet smell like maple syrup. Engine coolant has a sweet smell; if you notice this smell throughout the cabin or from the front of the car, you likely have a cracked or damaged coolant reservoir tank.

Generally, you can perceive the sweet maple syrup smell whenever there’s a leak from anywhere in the cooling system. And you need to diagnose and fix it as soon as possible.

Engine overheating

A damaged or cracked coolant reservoir will not be able to store the excess coolant in the cooling system or absorb the increased pressure, leading to engine overheating. When this happens, you will notice a fluctuating temperature gauge on the dashboard.

There could be other cracked coolant reservoir symptoms. But these are the most obvious ones that happen almost every time you have a cracked reservoir.

What causes the coolant reservoir to crack?

Like every other cooling system component, the coolant reservoir does not crack for anything. Here are what causes the coolant reservoir to crack.


Most reservoirs are made of plastic. With time, exposure to heat and pressure will cause the plastic material used in manufacturing the reservoir to become bristle and susceptible to cracking.

Poor maintenance

Another common cause of a cracked coolant reservoir is poor maintenance. Lack of proper maintenance can cause constant low levels of coolant, which could result in increased pressure in the system. And if the coolant reservoir is under too much pressure, it can cause it to crack.

Engine overheating

If the car overheats, it could cause the reservoir tank to crack. Overheating the engine will build much pressure in the coolant reservoir—causing it to expand when driving and contract when you shut off the engine. Over time, the expansion and contraction of the reservoir will cause it to crack.

Several factors, such as a bad radiator, a torn hose, low coolant levels, a faulty water pump, and a lousy thermostat, can cause engine overheating.

How to Check for a Cracked Coolant Reservoir?

The moment you notice any of the symptoms of a cracked reservoir tank, inspect the reservoir tank to confirm whether it is bad or not. You only need to run a visual inspection. 

Look for puddles under the car.

Start by looking underneath the car for a colored fluid. There are different coolant colors. But if the color underneath your vehicle is the same as in the radiator, the puddle is surely your engine coolant.

Check for cracks in the reservoir tank.

Look at the plastic reservoir tank and check for cracks if you notice any damages, repair or replace the tank.

Check the seal at the reservoir cap.

Open the reservoir tank and inspect the rubber seal at the cover. If the seal becomes brittle due to exposure to heat and much pressure, it will allow coolant to leak from the reservoir tank. Replacing the reservoir tank cover or the rubber seal will stop the coolant leaks.

How to Fix a Cracked Coolant Reservoir

The no.1 thing to do when you suspect your engine coolant reservoir is cracked is checking the system. If the test proves the reservoir tank is cracked, you have to either fix or replace it.

Repairing a cracked reservoir tank

If the crack in the reservoir tank is small, then you just have to fix it. Here are simplified steps on how to fix a cracked coolant tank;

  • Park the vehicle and allow it to cool before doing anything
  • Drain the coolant in the reservoir
  • Disconnect the upper and lower reservoir hoses
  • Remove the reservoir tank by removing the mounting bolts
  • Sandpaper the cracked area with smooth sandpaper so the sealant will sit properly
  • Apply epoxy resin or any other strong sealant on the sandpapered surface. Alternatively, you can get a coolant tank repair kit, which will enable you to fix any leaks in other cooling system components.
  • Allow the sealant to sit for 30 minutes to 1 hour so it can bond with the reservoir tank.
  • Reinstall the reservoir tank and re-connect everything you removed earlier
  • Refill the engine coolant to the recommended level.

Replace the reservoir tank.

If the crack on the tank is large, the best solution is to replace it. To do this, you will need to;

  • Drain the coolant on the reservoir tank
  • Disconnect the upper and lower water hose from the tank
  • Remove the bolts holding the tank in place
  • Install the new reservoir tank; tighten the bolts and connect the water hoses.
  • Pour in the recommended engine coolant. Ensure the coolant stays at the right level.

engine coolant reservoir cracked

How to Prevent Cracks in the Coolant Reservoir

Here are some of the tips you need to prevent cracks in the coolant reservoir;

Use the right type and amount of coolant.

Always use the recommended coolant when changing the old one. If you don’t have the recommended coolant, use distilled water when topping the coolant. Tap water will introduce foreign objects into the cooling system and lead to rust and corrosion.

Also, keep the coolant at the right level. When running low on coolant, too much pressure will build in the reservoir tank. This will cause expansion and contraction, leading to cracks in the tank.

Performance regular checks

Poor maintenance can result in inadequate coolant levels and increased pressure in the tank. Perform regular checks to ensure you maintain proper coolant level and there is no sign of wear and leaks; drain and flush the system every two years or 30,000 miles.

Avoid engine overheating

Engine overheating will increase the pressure in the radiator and the reservoir tank. Avoid engine overheating and fix it as soon as possible in case the car overheats.

Protect from physical damage.

Avoid hitting or damaging the reservoir tank when working in the engine bay. Sometimes, cracks in the coolant reservoir happen due to mechanical damage to the tank.

Benefits of Fixing a Cracked Coolant Reservoir

Here are some of the benefits of repairing a cracked coolant reservoir.

Prevents low coolant levels

Generally, a cracked coolant reservoir causes low coolant levels by leaking out coolant. By fixing the reservoir, you prevent the coolant from leaking out—maintaining appropriate coolant levels.

Maintaining right temperature

Engine coolant is essential for keeping the engine at the right temperature. By repairing a cracked or damaged reservoir tank, you keep the engine coolant at the right level—preventing overheating and temperature fluctuations.

Avoiding overheating and engine damage

Coolant leaks from anywhere in the cooling system will cause low coolant levels, overheating, and engine damage if the car continues running with low coolant levels for long. But by tracing the root cause of the leaks to the reservoir tank and fixing it, you prevent these damages from occurring.

Preserving cooling system efficiency

When the reservoir tank cracks, it will affect the efficiency of the entire cooling system. But by fixing it, you help the cooling system to dissipate heat properly and prevent overheating and other damages that could occur due to low coolant levels.

Saving money on repairs

Fixing a cracked reservoir tank the moment you notice it prevents the cooling system from running on low coolant. As a result, it leads to overheating and other engine issues. Aside from preventing these issues, it saves you money because it is cheaper to fix a cracked coolant reservoir than to fix an overheating engine.

How Much Does It Cost to Replace Coolant Reservoir?

A cracked coolant reservoir costs between $10 and $15 to fix if you are repairing yourself. You only need to buy epoxy for coolant reservoir or your preferred sealant and a piece of smooth sandpaper.

However, the typical cost of replacing the coolant reservoir ranges from $150 to $300, including the part and the labor cost.

Risks of Ignoring a Cracked Coolant Reservoir

It is important to check and fix a cracked coolant reservoir tank as it helps the cooling system to function properly and prevent overheating and other engine damages.

However, ignoring to fix a cracked coolant reservoir will lead to several issues, such as coolant leaks, engine overheating, engine damage, fire outbreaks, reduced engine performance, rust and corrosion in the cooling system, environmental impacts, and higher repair costs.

Final Words

To be precise, age and wear, overheating, too much pressure buildup, and poor maintenance are the most common causes of a cracked coolant reservoir. And the common signs to trace that issue include low coolant level, engine overheating, and coolant leaks. If you see any of these symptoms, inspect the reservoir tank for cracks and other damages by following the guides above.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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