7 Main Causes For Coolant Pouring Out Of Bottom Of Car!

While having a car, it is normal to face fluid leaking problems. But leaking coolant is mostly seen in old cars that have not been serviced for a long time. Many people have faced this problem and asked, why is coolant pouring out of the bottom of cars?

This issue could be due to coolant system-related damage. You may find coolant leakage while driving or standing. In both conditions, the reasons are almost the same. Diagnose the problem properly, and then take the proper measure to resolve the issue. 

Throughout this article, you will find a detailed discussion about the causes as well as the solutions of coolant pouring out of the bottom of the car.

Why Coolant Pouring Out Of The Bottom Of The Car?

Coolant pouring could occur due to several reasons, such as

  • Car hose leakage or the hose is so loose that the coolant is coming out
  • A leakage in the heater core
  • A damaged thermostat housing or radiator cap 
  • A broken radiator
  • Also, you should check the water pump and head gasket while detecting the problem as they can get damaged

Coolant keeps your car away from overheating. Pouring out of the coolant is surely a severe issue. 

The causes of pouring out the coolant of the bottom of cars are discussed below. The solutions to the causes are also discussed so that you can have a clear idea about what you should do. 

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Problem 1: Car Hose Or Bottom Radiator Hose Leaking

Radiator Hose Leaking
Radiator Hose Leaking

The hoses act as a pathway for coolant circulation, and the whole system is joined with the hoses by clamps. If you notice the coolant is leaking while driving, the probable cause is leakage in this hose, mainly in the bottom hose. It mostly occurs in old cars.

Consequently, while the engine heated up, the joint became expanded. It can not hold the hose tightly. That causes coolant loss while circulating. 

However, if your car only leaks while driving or the engine starts but not while the engine is off, it is due to the radiator hose leaking.


The best and easiest way to solve this problem is to use insulating tape to cover the leakage area tightly. This is a time-worthy process, and you can save money. 

But if this problem frequently occurs after covering or if you can not cover the leakage perfectly, go to an auto repair shop to fix the problem properly.

Problem 2: Leakage In Heater Core

 Leakage In Heater Core
Leakage In Heater Core

Another cause of coolant leaking is a damaged or leaky heater core. The heater core also helps to cool down the engine by air passage. But if it is damaged, you can see coolant leaking from the car, especially behind the dashboard or from the bottom of the car.

Also, a bad heater core does not allow the engine to cool down. Rather it helps to heat the engine. Heating for a long time frequently causes the hose leakage or loss of the hose connection and coolant leak.


You need to replace the heater core to resolve this problem. Follow the steps below to do this. 

  • Step 1: Drain the coolant
  • Step 2: Unplug the two heater feed hose from the heater core
  • Step 3: Now carefully remove the heater core outside
  • Step 4: Place the new heater core (Our Pick) back in the old position. Make sure the heater core does not scratch any part
  • Step 5: Remove the O-ring from the hose and wipe the connecting part of the rod with a cloth
  • Step 6: Place back the two new O-rings provided with the heater core
  • Step 7: Push the hose back to the holes of the heater core and tightly connect them

Problem 3: Broken Radiator

Broken Radiator
Broken Radiator

The radiator helps to remove heat from the coolant. If there is any corrosion present in the radiator or it is broken, the cooling system will not work properly. 

Besides, the effects of using different kinds of coolant can hamper the radiator’s performance and cause leakage. Also, if the tube in the radiator gets old, there will be leakage.


To solve a radiator-related problem,

  • Clean the core timely, as too much dirt hampers the air-passing system
  • Dry it before installing it
  • Replace the radiator (Our Pick) if it is damaged or too old to work well

However, do not replace the radiator by yourself if you have less experience, as the new one can also get damaged.

Problem 4: Damaged Thermostat Housing

The leakage could be for a bad thermostat housing or leakage. Also, if the thermostat valve is closed, the leakage of coolant will increase.


First of all, you have to tighten the thermostat housing. If that does not work, replace the thermostat housing. Follow the steps to do that. 

  • Step 1: Let the engine cool down properly
  • Step 2: Drain the coolant into a drain pan
  • Step 3: Remove the hose clip that holds the hose to the thermostat housing
  • Step 4: Carefully remove the hose from the thermostat housing
  • Step 5: Now unscrew the bolts from the mounting hardware
  • Step 6: Remove the thermostat housing
  • Step 7: Clean the dust from the thermostat holding hose
  • Step 8: Install the new thermostat housing (Our Pick) in the same manner as the previous one
  • Step 9: Tightly screw the bolts
  • Step 10: Put the hose back in position and keep the clamp back to the connection
  • Step 11: Now fill the reservoir with clean coolant

Before driving, check if the leakage is gone or still present. Start the engine and keep it on for five to ten minutes. Check underneath the car.

Problem 5: Leakage In Radiator Cap Or the Cap is Damaged

The radiator cap regulates the excess pressure of the coolant so that the hose or radiator does not get damaged or prevent overflow. When the engine heats up, the volume of coolant expands. Then the safety valve goes off, and the coolant goes back to the header tank.

But if the radiator cap is damaged or a leak is present, or the pressure release valve fails, the spring compresses. Thus, the rubber can not limit the excess pressure. For that reason, the coolant will leak and pour out from the bottom of the car.


Inspect the radiator cap and make sure the rubber is not soft or expanded. Put it on the cooling system pressure tester to ensure that it is working. If it is not working, replace the radiator cap (Our Pick) with a new one mentioned in the manual.

Problem 6: Damaged Or Blown Head Gasket

If the coolant is not leaking for all the above reasons, it must be leaking for a blown head gasket of the combustion engine. It not only creates leaking issues but also can contaminate heated gasses with coolant. A damaged or failed head gasket can affect engine performance and create overheating issues.


The only way to get rid of this problem is to install a new head gasket. Buy a new one according to the car manual. It is better to do the installation with an expert hand.

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Problem 7: Broken Water Pump

The function of the water pump is mainly to circulate the coolant from the radiator to the engine and the engine to the radiator when needed. It has many gaskets and can cause blow out. Also, the water pump could be damaged. Ultimately it will result in coolant leakage.


Replace the water pump with a new one.

  • Cool down the engine and drain the coolant
  • Remove the cables from the battery then the battery and battery box
  • Now carefully remove the serpentine belt
  • Unscrew three bolts and remove the pulley and remove the water pump
  • Now clean the gasket material from the surface
  • Now hold the new water pump in position
  • Keep the bolts in position 2 bolts in a similar manner to the old one
  • Now place the pulley and install the bolts
  • Place the serpentine belt back in position
  • Now place the battery box and the battery and connect the cables
  • Add a new coolant and ensure that the coolant is not leaking underneath the car

You can change it by yourself, or you can go to a local auto repair shop. Replacing a water pump will be relatively expensive.

Frequently Asked Questions (FAQs)

These are the commonly asked questions by people about coolant pouring out of the bottom of the car. Have a look. 

Can I add more coolant to my car if it is leaking?

No, you should not add more coolant if your car is leaking. If you add more, that will also pass through the leakage and can not cool down the engine properly. So, first, correct the internal problem, then add coolant.

Can coolant leakage cause car overheating?

Yes, coolant leakage can cause overheating issues. Coolant is the main substance to cool down the engine. If it leaks and remains at a low level, then the engine can not get enough fluid to transfer the heat, and this results in overheating issues.

What are the symptoms of coolant leakage?

The most common symptom of coolant leakage is overheating of the engine. There will remain coolant under the car. Also, you will get a sweet aroma after every ride.


Everyone with a car faces a fluid leaking problem in their life. Either the leakage is related to engine oil or coolant or brake fluid. Sometimes the problem is due to leakage in the system or that could be the result of contamination. Like if there is any damage in the engine cooling system, the common result is coolant leakage.

Coolant leaking problems could arise due to a damaged heater core or water pump or leakage in the head gasket of the engine. If you do not want to face this problem, the best way is to keep your car under regular servicing. Because if the leakage is due to a vital part like the head gasket or water pump, it will cost a lot.

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