Cooling System Repairs

Cooling systems on modern European and British vehicles are quite complex and require maintenance and occasional repairs/replacements to ensure the safety of the engine and to prevent costly breakdowns.

This article will shed some light on what a typical cooling system consists of and what problems can occur.

Cooling System Components

The major components of the cooling system are the radiators, cooling fans, water pumps, thermostat, hoses and pipes, heater core, temperature sensors, and the coolant itself.

Engine

The engine has coolant passages throughout the block and cylinder heads to carry heat created by the combustion process away to the radiator where the heat is transferred to the air flowing over it.

Radiators

The radiator is basically a collection of small tubes with cooling fins on them with tanks on either side. Coolant enters one tank and travels through the tubes to the other tank and back into the system having been cooled by air flow over these tubes/fins.

Fans

This air flow is maintained when the vehicle is not moving or moving slowly by mechanical fans with a fan clutch or electric fans or both. These fans are active when additional cooling is needed and are usually not working when driving at road speed.

Coolant

Coolant is more efficient than plain water at absorbing/transferring heat and it also lubricates the water pump, prevents corrosion, and prevents freezing or boiling. Too much coolant can actually be worse and reduces the efficiency so its important to have the correct ratio of coolant to water.

Water Pumps

This coolant needs to circulate which is where the water pump comes in. Most cars have a mechanical pump turned by a belt but some have an electric water pumps controlled by the engine computer.

There are also auxilliary electric pumps that circulate coolant through the heater core or additional, smaller radiators or coolers for turbocharged or supercharged vehicles that share coolant with the main system or have their own closed system.

Thermostat

The thermostat is critical for the operation of the entire cooling system because it regulates how much coolant circulates and when. When the engine is cold, the coolant flow through the radiator is cut off by the thermostat so that the engine can reach operating temperature quickly. As you drive your vehicle, this thermostat is opening and closing to maintain the optimal temperature for the engine to be efficient without overheating. Some vehicles also have an oil thermostat that behaves the same way but for oil coolers.

Heater Core

The heater core is not directly related to engine cooling, but it is a main component of the cooling system. It is a mini radiator located in the dash that coolant flows through to provide heat for the interior of the car. Depending on the car, coolant flow is turned on or off or coolant is always circulating through the heater core and air flow is directed over it or diverted away.

Expansion Tank

The expansion tank or coolant reservoir is where you usually add coolant to the vehicle and they provide a buffer for the cooling system as the liquid expands and pressure builds. They should never be filled to the top to allow room for expansion. On the expansion tank is a cap that is made to relieve cooling system pressure if it goes over a set amount to avoid damaging other parts of the system in the event of overheating.

Very old vehicles did not have a pressurized cooling system, and did not need an expansion tank. Most European and all newer vehicles have a pressurized cooling system to increase the heat capacity/efficiency and prevent boiling.

Hoses, Lines, and Pipes

The last part of the system are the hoses and pipes that tie it all together. These are typically a combination of rubber hoses connected with clamps or quick connect fittings with o-rings, hard plastic lines, or metal pipes that connect to rubber or plastic lines.

What Goes Wrong?

Cooling system problems can be as complex as the system itself, but the biggest enemy of cooling systems is usually leaks. Leaks can be caused by ageing components degraded by wear and tear or heat or by physical damage such as a rock puncturing the radiator. Leaks can also be caused by excess pressure in the cooling system from overheating if a water pump fails, thermostat doesn’t open or fan stops working.

If the vehicle does overheat and cause a leak, some times fixing the main leak will result in other leaks popping up in other components, especially if the vehicle is older or higher mileage. This is why using a pressure tester on the vehicle is crucial following a repair. Even with that, other leaks can pop up days or weeks after.

Leaks or a weak expansion tank cap results in low coolant and air entering the system. This creates air pockets which can result in a failure to circulate coolant or transfer heat. When cooling system repairs are carried out, it is crucial to use a vacuum filling system to remove air from the system. Modern cars have too many components to properly refill without this important tool.

The other two most common failures are a failed thermostat or failed water pump. If the thermostat fails open, this is only an issue for efficiency and will not cause overheating. If it fails closed, coolant is never allowed to circulate fully and the engine over heats. If the water pump fails, coolant will not be pump through the system and the engine will overheat as well.

In less common instances, usually from poor maintenance of the cooling system, improper repairs, or mixing the wrong coolant types, the radiator can become clogged. Depending on the severity, this can either result in reduced cooling performance leading to elevated temperatures in traffic, or a complete lack of circulation leading to overheating in a short amount of time.

The coolant used in Land Rovers and Jaguars can also create deposits/clogs if the vehicle is driven with leaks for an extended amount of time and air is allowed to enter the system over and over.

Another main cause of overheating is a failure of the cooling fans. Most vehicles have either a mechanical fan and an electric fan, or two electric fans. One is usually for the A/C and comes on when you turn on the A/C to provide extra cooling for the condenser, the other fan or mechanical fan is for the engine when it goes over a certain temperature while driving in slow traffic or sitting at idle. If the fan(s) fails when the vehicle is not at speed, the temperature goes above the safe range, the cooling system pressure increases, and either the expansion tank cap blows off excess pressure and coolant or a component will fail and leak.

A lot of newer vehicles have digital temperature gauges or overheating lights so you may not know there is a problem until the vehicle has already overheated. This is why it is important to have your vehicle regularly serviced at a shop that checks for leaks and proper operation of the cooling system during oil service or other repairs.

Summary

This article only covers the most broad, basic overview of the cooling system, but hopefully it clears up some of the mystery around what keeps your car’s engine cool.

Replacing key components when they show signs of failing or leaking is critical to prevent break downs or engine damage. Regular testing and flushing of the coolant ensures a clean, efficient cooling system. Consistent service and checks catch problems before they become worse.

Luxury vehicles may not come to mind when you think of high performance, but their engines and surrounding systems are amongst the highest performance most complex in the car world and their cooling systems reflect this performance and advanced technology.

Contact us today to schedule a vehicle service to check your cooling system and avoid costly break downs in the future!