Oil coolers: how they keep your car cool and what can happen when they break

Oil coolers: how they keep your car cool and what can happen when they break

Since oil is the lifeblood of your car, you have to make sure that blood doesn’t boil. Find out how an oil cooler stops this from happening.

When it is the depths of winter, you’re struggling to shift ice off the windscreen, and your breath is misting up even inside the car, a cooler for your engine oil might be the last thing you think your car needs. But regardless of the weather, engine oil gets very hot inside your engine.

The constant movement of the pistons and other moving parts which keep the engine going creates a lot of heat through friction and it is part of the job of engine oil to take away this heat. While oils are designed very well to do this, especially full-synthetic engine oils with additives, they can take all the help they can get, and this is where the car oil cooler comes in.

Helping to keep the oil and your engine cool, this unit is a key part of the car’s cooling system and although most drivers will never have any interaction with their oil coolers, keeping them in working order will make sure they last longer. Just like any other component, they wear out over time, so use our guide to find out what an oil cooler is and how to properly maintain it. You could even think about upgrading your oil cooler!

What is an oil cooler in an engine?

What is an oil cooler in an engine

The first question that lots of people ask is ‘is an oil cooler a radiator?’. In essence, yes, it is a small radiator that does the same job as a normal radiator for oil. The oil cooler purpose is to allow the engine’s cooling system to remove excess heat from the oil. They look like small cross-flow heat exchanges and the oil cooler location can differ depending on which car you have, though they are all played to maximise the cooling efficiency.. With oil coursing predominantly through the engine block, the steering system, and a turbocharger in turbocharged vehicles, oil can very quickly gain heat, especially when driving intensely.

In most cars, engine oil is fed to the oil coolers from an adapter that is located between the engine block and the engine oil filter. The oil then flows through the tubes of the cooler while the engine coolant flows around the tubes. The heat from the oil is transferred through the walls of the tubes to the surrounding coolant similar in many ways to the operation of an indoor air conditioning for residential homes. The heat absorbed by the engine’s cooling system is then transferred to the air as it passes through the vehicle’s radiator, which is located in front of the engine behind the grille of the vehicle.

Why is it important to keep engine oil cool?

Oil flows around the engine block

Oil flows around the engine block to make sure moving parts are lubricated and can move freely and also to remove heat produced through friction. Before the oil enters the sump or oil reservoir after it has been around the system and will be sent around once more, it needs to be cooled down so that the oil doesn’t reach an unusable viscosity. Viscosity is a measure of how easily a fluid flows, and as oils lose and gain heat, their viscosities increase and decrease respectively. So a thick, lumpy oil has a high viscosity and a smooth, thin oil flows more easily and therefore has a lower viscosity.

Automotive oils are specially designed to sit within certain ranges of viscosity. Therefore, if too much heat is transferred to the oil, its viscosity decreases to a point where it would struggle to lubricate the required systems properly. So it becomes a balance; you want it to be sticky enough to cling to the gears and moving parts, but free enough to flow through the system and keep it cool. Since temperature is an important factor in the change in viscosity of oil, cooling becomes an essential process.

How long does an oil cooler last?

An oil cooler is meant to last for the entire life of a car. This doesn’t mean, however, that it will last that long in reality as there are a few things that can go wrong. It is important to keep an eye out for any of the symptoms listed below. In certain situations, the cooler might have to be replaced, but it is hard to say exactly when. The sooner you spot the faults, though, the less damage will need to be repaired.

If you are getting your car serviced, they will normally check the oil and filter as well. Check that they check the oil cooler at the same time.

Why else are oil coolers important?

Oil coolers are incredibly important for cars with turbochargers. One of the most common reasons for turbocharger failure is inadequate lubrication. If the turbocharger doesn’t get oil, the high speed is going to cause a lot of damage in a very short time. The oil needs to stay at precisely the right viscosity so it needs to be kept cool and at just the right temperature.

Some turbochargers opt for a water-cooling system that improves mechanical durability and lengthens the turbocharger’s life. Many turbochargers are designed without water cooling ports and are sufficiently cooled by air and the lubricating oil that flows through them. Some even have both and are cooled by oil and water. Either way, keeping the turbo cool is important for it running. The oil cooler temperature needs to remain as stable as possible.

What are common oil cooler problems?

There are a variety of different issues you can get with an oil cooler and most of these will need certain components or even the cooler itself to be replaced.

A problem that you might encounter is that the oil cooler adapter, which connects the cooling lines to the cooler itself, fails. The gasket or rubber o-ring within the adapter can become hard and inflexible over time, which means that it does not act as an effective seal.

The lines themselves or the oil cooler can also fail and begin leaking, which would result in a loss of engine fluid. This can happen as a result of general wear and tear.

It could also be the case that coolant can be forced from the cooling system into the oil pan, if the engine is not running and the cooling system is pressurized.

What are the signs of oil cooler failure?

What are the signs of oil cooler failure

The common oil cooler failure symptoms usually relate to leaking liquids. If the oil cooler adapter fails as mentioned above, engine oil may be forced out of the engine. If it is only a small oil cooler leak, it might be a puddle of engine oil on the ground underneath your vehicle or if it is larger it could quite possibly be a stream of oil on the ground behind your vehicle. If either of these is the case, you should get it checked out at a garage as soon as possible. As oil leaks, the engine loses ability to lubricate itself. This could result in increased engine temperature and premature parts wear due to increased friction from the lack of proper lubrication.

Another liquid that the cooling system can lose is engine coolant. Similar to a loss of oil, engine coolant can leak out of an oil cooler if the body of the cooler is compromised. Whether the coolant leak is large or small, the engine is going to overheat after a while if it isn’t repaired quickly. If the leak is small, you may notice coolant puddling on the ground underneath your vehicle. If the leak is a large one, you will probably notice steam pouring out from under the bonnet of your vehicle. If enough coolant leaks from the radiator or oil cooler, it can result in engine overheating problems and mechanical component failure, so get it checked out as soon as possible!

Mixing liquids can also be a sign of a problem with the oil cooler. If the oil cooler adapter fails internally (rather than externally, as mentioned above) you may notice engine oil in your cooling system. This happens because when the engine is running, oil pressure is greater than cooling system pressure. Oil is forced into the cooling system. This will eventually cause a lack of lubrication and can severely damage your engine. This can also happen in reverse and coolant can get into your oil supply. For both of these, the cooling system and the engine both need to have all the liquids flushed out. If your oil cooler adapter has failed, this will need to be replaced. The oil cooler itself will of course need to be replaced if there is a leak.

If you have to repair your oil cooler or aren’t happy with how it is performing, you could think about an oil cooler upgrade. There are a variety of aftermarket kits available.

Oil Cooler Upgrades

Oil Cooler Upgrades

Most cars won’t need an oil cooler upgrade. For everyday use, cars will only ever need the natural cooling effects of the oil lying in the sump or coursing through other areas of lower temperatures to stay within the required viscosity limits.

If you’re planning on taking your car to a track day, fitting it out for proper racing, or doing a lot of off-roading, you might want to think about changing your oil cooler to something better. Most normal road cars aren’t designed to be thrashed around a track for lap after lap. Engine modifications may also bring the need for an oil cooler to the front of the shopping list. As an engine produces more power, it naturally creates more heat energy which will then transfer to the oil. If this level of heat transfer is above what the original engineering was specced to cope with, then measures will need to be taken to remove this additional heat from the oil system.

There are a couple of different options you have here, but a front-mounted oil cooler is possibly the simplest addition to your car. Sitting in or beside the radiator, a small heat exchanger should be able to cool the oil in an average sporty car, without taking too much away from the water-cooling system.

Comments – 4

  • @user_155181
    20.01.2022 22:39

    Hello Den,

    Am troubled.My BMW X3 has oil cooling system gone south. What started as a whitish cream on the wall of reseroir has now gone itno a lava flow (whitish/brownish/vanilla) MIXTURE oozing out of radiator.This despite the mech having changed the same twice since mid of dec 2021.Any Help Sir.

  • @Anna Johnson
    31.01.2022 13:15

    According to the description, it looks like the cylinder head gasket has been pierced, check it, and contact the service centre for a complete diagnosis, if this is not it is because there can be many reasons.

  • @R. P.
    25.04.2023 19:41

    So I have a 1.8t golf and have recently had the head gasket replaced, I don't really use the car yet it just sits on my driveway but the coolant keeps disappearing and ends up in the oil pan?? No oil goes into the coolant tho? So could this be the cooler??

  • @Anna Johnson
    03.05.2023 12:42

    Without proper diagnosis it is difficult to say something, it is recommended to contact the service.

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