Why is there a leak in my cooling system?

A leak in the radiator or cooling system of a vehicle can be a sign of two things: 1. Damage or wear and tear on the expansion tank, radiator or other element of the cooling system, or 2. Back pressure caused by a blown head gasket causing damage to the cooling system from the inside

How does damage occur through wear and tear?

As a vehicle ages, internal components become worn and, in systems which contain liquids, leaks can occur. There are many areas within a cooling system where contaminants within the coolant can wear away at the channel boundaries eventually wearing through and causing a leak, or simply where external damage can cause splits in containment material allowing the coolant to escape.

If this is the case, it is important to repair the leak to prevent the vehicle from depleting its coolant and subsequently overheating. There are many stop-leak products on the market which can simply be poured into the cooling system and will plug the leak without hindering the usual workings of the cooling system.

What causes back pressure?

The head gasket acts as a seal between the combustion chamber, which contains exhaust gasses, and the cooling system. When the head gasket is damaged, the compressed exhaust gasses can escape into the coolant creating excess pressure within the cooling system.

The cooling system is designed to handle the pressure of coolant circulation, but not the considerably higher pressure of exhaust gasses forcing their way out of the combustion chamber. Therefore certain channels and, in particular, the plastic expansion tank and other external elements of the cooling system, such as the radiator, are prone to damage and splits resulting from the excess pressure, creating a coolant leak.

Loss of coolant through a leak can cause further damage to the head gasket, as without coolant the engine’s optimal running temperature cannot be maintained, putting components (including the already-damaged head gasket) under excess pressure and causing further damage.

Why should I get my coolant leak diagnosed?

A leak attributable to wear and tear is easily fixed and relatively harmless. However, a leak resulting from the back pressure of a blown head gasket is critical.

The gasses in the combustion chamber are under a lot of pressure which is essential to the healthy running of the engine. If the exhaust gasses are escaping into the cooling system, the combustion chamber will begin to lose compression and the engine will struggle to function as normal, losing power and eventually failing to start at all.

My vehicle has a coolant leak: What should I do?

If you have a coolant leak, take your vehicle to a mechanic to diagnose the cause of the leak. If the leak is a result of wear and tear, you can use a pour-in cooling system repair such as Coolant Seal to fix the issue for less than £10. If the leak is a result of back pressure, research your head gasket repair options.

How much does it cost to fix a blown head gasket?