How To Repair A Coolant Leak

It might surprise you that this small cup could lead to leaking. The radiator contains a great deal of pressure and the radiator cup should hold it all in place. When operating properly, the cup forms a solid, reliable seal that ensures the system runs with optimal pressure. Over time, the seal can start to deteriorate allowing the coolant to leak out.

It can be surprising to walk up to your car and discover a pool of green liquid forming under it. You have no idea what it could be but think it can’t be good news. What you probably don’t know, it could be any number of things including coolant or antifreeze which can easily be fixed.

In this article, we will talk about how a coolant leak could happen and how to repair it so you can get back on the road.

What is Coolant or Antifreeze?

Anti-Freeze Leak

Coolant is a fundamental fluid needed to keep the engine of your car operating at the required temperature. The coolant will maintain the right temperature even during freezing or hot weather.

Coolant or antifreeze is made of silica and ethylene glycol. When mixed with water, it forms the coolant.

Why Would The Coolant Leak?

Usually, a coolant leak is caused by a leak in the radiator hose or the radiator is leaking. Other cases could be a dysfunctional water pump or a failed expansion tank. Leaking coolant is found around hose clamps or from cracks in the tubes within the cooling system.

Here’s a list of possible causes of coolant leaks:

A Hole In The Radiator

Because of its physical location, a radiator goes through a lot of abuse. Corrosion is probably the leading reason why the radiator fails. The corrosion forms holes which will lead to leaking.

The sealing gasket is located between the radiator and tank which if worn out will start leaking. Another reason, one of the hoses connected to the radiator has become brittle and failed.

A Leaky Radiator Cup

Oxygen sensors are in place to measure how much oxygen is leaving the system through the exhaust. If there is too much or too little oxygen leaving, the ECU is going to adjust the air-fuel ratio to balance out the performance.

A faulty sensor can send wrong information back to the computer causing you to adjust things that should be left alone. You could cause an imbalance in the air-fuel mixture which can cause poor performance and lead to engine issues as well as set off the Reduced Engine Power Warning.

A Blown Head Gasket

The head gasket keeps the engine oil and coolant separate. If the gasket fails, you probably won’t even notice it because the leaking will be internal. That said, you might see coolant in the engine oil. If you will notice the engine temperature rising and the coolant starting to leak outside of the engine, it could lead to a serious situation.

A Dysfunctional Water Pump

The water pump circulates the coolant throughout the system. Normally, the pump is driven by a belt. The belt connects to the engine crankshaft but can be at the mercy of leaks and corrosion.

The water pump can be damaged from external issues, leading to leaks. If the pump is not working properly, the coolant cannot move around properly causing the engine to overheat.

A Damaged Expansion Tank

Car Coolant Tank

The expansion tank is a plastic container that holds the coolant and sits next to the engine. It is connected with a hose to the radiator. Its purpose is to deliver coolant to the radiator when needed. Over time, the container can wear out and easily crack then start leaking. Also, the hose can deteriorate and start leaking as well.

There are many reasons why antifreeze will leak and there are several remedies to repair the leak. We recommend you simply replace the part that is leaking, but there are other methods you might choose.


If you are nowhere around civilisation and the radiator starts leaking and you just happen to have eggs in the trunk, you might be able to buy some time until you get to a place for repairs. This is not the best option but it will work temporarily.

Allow the car to cool down then unscrew the radiator cap. Crack a few eggs and place them in the radiator reservoir. If it continues to leak, add a few more eggs. The eggs will be pushed out of the holes and then clog up the holes to stop the leak temporarily. Keep in mind, that eggs can also cause further damage, and therefore it’s not recommended by mechanics.

There are other additives to fix coolant leaks but can also cause clogging, so use with discretion.

Replace The Clamps

All the hoses are held in place by clamps. If a clamp is damaged by corrosion, you will have to replace it.

Let your car cool down then find the defective clamp. You might have to dump the coolant into a bucket if you cannot reach it. Remove the damaged hose and the old clamp then put on the new clamp and make sure it’s properly tightened down.

Fill the radiator with fresh coolant and tighten down the cap. Turn on the car and let it run until it reaches the correct temperature. Look around and make sure there are no other overlooked leaks.

Replace Coolant Tank Clamps

Replace The Hoses

Allow the car to cool down then find the faulty hose. You might have to drain the coolant into a bucket. Take off the clamps holding the hose. Replace the hose with a new one and clamp it down. Fill the system with fresh fluid and run the car to check for any other leaks.

Replace The Radiator

Keep in mind, radiators can be installed differently depending on the car manufacturer but some of the steps will be the same.

Allow the car to cool down and disconnect the battery. Drain all the coolant from the system by pulling the plug on the bottom of the radiator. Make sure to dispose the coolant properly.

Remove all hoses that connect the radiator to the engine and take off the thermostat. There is a fan mounted to the radiator that should be removed. Remove the bolts holding the radiator to the mounting bracket.

Remove the old radiator and replace it. Put everything back together in reverse, replacing any worn-out parts during this time. Fill up the radiator and start your engine to check for any further leaks.

If you are having issues with your vehicle and a possible coolant leak you can get your vehicle checked and the issue diagnosed and resolved by booking online today.

For further information on our services you can browse the site or get in touch with us by calling 019253 30468 or alternatively, you can email us directly at At Lowton Motor Company we service all vehicles produced by all the top manufacturers from the a Kia to a Porsche and everything in between. Our experienced technicians have access to and traning with all the latest technology. You can be sure your vehicle is in safe hands whether it’s in for a repair, a service or just the annual MOT.

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