Coolant system check on a Range Rover Classic

A cooling system check gives reliability and peace of mind. Alisdair Cusick and Ed Evans explain how and why.

In the process of burning fuel, the internal combustion engine develops heat as a by-product of the cycle. All engines, be it petrol or diesel, need a way to dispose of that heat, otherwise the moving internal parts would simply overheat and eventually jam or weld themselves together. There are two main ways of cooling an engine: air or water.

Air cooled engines usually work by air blowing over cooling fins on the cylinder heads as seen on motorbike and early Porsche engines. Water-cooling, used on Land Rovers, relies on water circulated through passages inside the engine by a coolant pump, and delivered to the radiator where it is cooled by air flowing through the matrix (assisted by the engine fan).

Once cooled, the water flows from the radiator back into the engine to remove more heat. To help warm up the engine faster from cold, and thus use less fuel, a thermostat reduces the flow of coolant to the radiator until the most efficient temperature is reached. Then the thermostat opens, allowing full flow around the system. Simple, but effective. 

Advertisement - Article continues below
Advertisement - Article continues below

The coolant operates typically between 90 and 110 degrees C. It doesn’t boil because the coolant system is sealed via a screw cap on the coolant header tank, so the pressure increases when it is hot, which increases the boiling point. Thus, a slight leak allowing the system to lose pressure, will result in the coolant boiling. Also, antifreeze additive raises the boiling point, lowers the freezing point and prevents corrosion inside the system. To achieve that efficiently, the antifreeze needs to be mixed with water in the ratio specified for your model. 

Antifreeze finds any sort of gap, so under working pressure it will leak from hoses that aren’t tight, worn water pump seals, aged gaskets, or corroded radiators. Leaks mean a slowly lowering level in the system, which eventually depletes the cooling ability. To maintain effectiveness, the fluid also needs draining and refreshing to the correct dilution at regular intervals of usually two or five years, or even 10 on later models, depending on the type of coolant used and the model specification.

Advertisement - Article continues below
Advertisement - Article continues below

But it’s a quick, easy job to check over the system, spot problems before they get to the point of causing a failure, and even to drain and refill the coolant. We’re looking at a late Range Rover Classic here, but the basic principles are the same whether you have a Series vehicle, or a modern Land Rover. Always allow the engine to cool and the coolant to depressurise before working on any part of the coolant system.

Heater matrix

Leaks from the heater matrix which is usually hidden behind the dashboard on all but Series and Defender models can be difficult to identify. Leakage from the matrix can be caused by overheat, mechanical damage from vibration and internal corrosion if antifreeze servicing has been neglected.

Irritatingly, it is usually a big job to sort on anything other than a Series or Defender. When a vehicle is assembled, the heater matrix is usually one of the first components to go on the bare shell. To replace one, means you may have to strip out the dashboard or facia.

Advertisement - Article continues below
Advertisement - Article continues below

If you’re losing coolant and can’t trace a leak elsewhere on the system, check the carpets behind and under the dash. A heater matrix leak usually shows as a stain to the carpet, or slippery/sticky moisture – not to be confused with a leak from the air conditioning moisture drain, which will be clean water.


Thermostats RARELY give trouble, but you’ll know if one fails because the engine will take an unusually long time to warm up, if indeed it warms up at all. Thermostats are designed to fail in the open state, so that, rather than restricting the coolant flow during the warm up period, they allow full flow of the coolant.

Check your thermostat by feeling the top hose downstream from the thermostat itself. The hose should stay cold as the system warms, then get hot as the thermostat opens, usually around 80 degrees or so. Keep fingers well clear of the cooling fan and drive belt.

Types of anti-freeze

There are two types of antifreeze: silicate-based Ethylene Glycol (EG), used typically until 1999, and Silicate-free Organic Acid Technology (OAT), which has been widely used since then. Most Ethylene Glycol types need changing twice yearly. The OAT type is serviceable for five or 10 years. It’s essential to follow the recommendations in your vehicle handbook regarding the type of antifreeze needed, and the renewal frequency.

Advertisement - Article continues below
Advertisement - Article continues below

OAT is red in colour, and Ethylene Glycol can be blue, green or yellow. You can mix different colours of Ethylene Glycol, but you must never mix OAT and Ethylene Glycol, as it can react and form a jelly which can block coolant passages. Antifreeze has service intervals because it loses its corrosion protection over time, due to engine heat and the mechanical action of the pump.

For vehicles in long term storage, so long as they have a good mix of antifreeze, the frost protection of the engine is maintained. Correct servicing is always key, but it’s good to know the engine shouldn’t crack over a winter.

Tools needed – small socket set, funnel, oil catch tray, antifreeze tester

Time: 1 hourCost: £22

Health and safety

• If the coolant system needs to be inspected while hot, avoid squeezing or moving hoses, and wear eye protection and gloves • Escaping hot coolant will soak through gloves and scald the skin, so pull gloves off quickly when wetted • Never open the coolant filler cap when the system is hot and, even when cold, beware of residual pressure• Always switch the engine off before inspecting the system, and beware of electric fans starting up independently

Click on the gallery below for our handy step-by-step guide…



Jaguar Land Rover Project Vector - front

New JLR Project Vector showcases autonomous future

The new JLR Project Vector autonomous pod sits on a new platform and is scheduled for on-road trials before the end of 2021
18 Feb 2020
Land Rover Discovery 2017 - official incontrol touch pro
Land Rover

What is Land Rover InControl?

Here’s everything you need to know about Land Rover’s InControl infotainment system
11 Feb 2020
OPINION Sir Ralph Speth

'The JLR management merry-go-round is up and running'

With JLR CEO Sir Ralph Speth retiring, Steve Fowler looks at who in the automotive industry looks set to replace him
5 Feb 2020
Opinion - Jaguar E-Pace

“JLR desperately needs a range of smaller cars and SUVs”

Could Jaguar Land Rover become the latest brand to join the PSA empire? Mike Rutherford thinks it would be a good idea for both parties
26 Jan 2020

Most Popular

Bentley Continental GT

Bentley’s built a horse-themed Continental GT Convertible

The bespoke Continental GT Convertible Equestrian Edition features tweed door panels, a walnut dash and gold “horse and rider” emblems
9 Mar 2020

Most Wanted Cars 2020: poll

Decide which classic car you would most want to see brought back from the dead by an all new model
27 Mar 2020
BMW 4 Series

New 2020 BMW 4 Series spotted undergoing development

A near production-ready version of the latest BMW 4 Series Coupe has been spied, wearing a pair of huge kidney grilles.
19 Mar 2020