Oil cooler leaking / defective? Symptoms, repair and costs!

Recently updated on January 27, 2022 at 10:19 am

Vehicles with standardized engines have so-called Oil Coolerwhich are usually in the immediate vicinity of the engine and are integrated directly into the cooling system. Vehicles with a higher engine size also have air-cooled oil coolers that are located behind the bumper. And modern vehicles even have map-controlled oil coolers, in which the cooling is varied depending on the current operating status.

Defective oil cooler - causes / signs

Poor workmanship and wear due to aging can be the cause of a leak and a defect in the oil cooler. The following symptoms are expressed here:

• Detection of a loss of cooling water in the expansion tank
• Dark or milky cooling water by mixing with oil
• The cooling water expansion tank is dark or black
• Possible message from the on-board computer that the cooling water needs to be checked

Attention: Do not open the expansion tank for the cooling water until the engine is cold, as there is high pressure in the tank due to operation. Otherwise there is a risk of scalding!

Used car check before buying

You should definitely check the above symptoms before buying a used car. A look into the coolant expansion tank will tell you whether the oil cooler is leaking or defective. It is important to check the container for oil residues.

Defective oil cooler - continue driving or repair immediately?

If you suspect a defective oil cooler due to a loss of cooling water or mixing of the cooling water with engine oil, you should not hesitate and go to a workshop as soon as possible. Otherwise there is a risk of engine damage as the cylinders are no longer adequately lubricated and cooled.

Confirmation of diagnosis by the workshop

In practice, oil in the cooling water tank indicates a defective oil cooler. But it can also be a defective one Cylinder head gasket be responsible for the problem. In the case of pure cooling water loss, however, there can be several causes. Maybe just one connector is defective? That would be the most favorable situation with a high probability! To be on the safe side, the oil cooler should be removed by the workshop and checked using a pressure test. In this way, either the diagnosis of a defective oil cooler can be ensured or, in case of doubt, another cause of the symptoms can be looked for directly.

Defective oil cooler - repair or replace?

If the diagnosis is confirmed, the defective oil cooler should be replaced. A repair does not make sense in the case of a defective oil cooler. You should also keep your hands off used oil coolers, as oil coolers are wearing parts. The reason for this is the relatively high amount of work involved in changing the oil cooler. A replacement with a new component should therefore preferably take place in order to save follow-up costs due to a further replacement due to a defective used part.

sometimes extremely high effort

The cost of a change can vary greatly depending on the vehicle and construction. The change usually starts with draining the cooling water and dismantling the hoses and lines of the oil cooler. The defective oil cooler is then removed and replaced. As already emphasized, the change can also be more complex if the construction requires additional dismantling of the front turbocharger or the Intake requires. In the worst case, the engine may even have to be removed if access to the oil cooler is not otherwise accessible. Corroded lines and connections that are not or difficult to detach can also contribute to increased expenditure. Such work should always be carried out by a specialist workshop, because on the one hand the guarantee plays a role and on the other hand the cooling system has to be flushed with a special cleaner.

Costs depend on the motorization!

The higher the motorization, the higher the costs. It is not possible to quantify the costs precisely because the cost of a repair or a change varies greatly from vehicle to vehicle.
The costs for changing an oil cooler cannot therefore be quantified across the board, as the workload varies greatly depending on the vehicle. However, three examples of the costs of replacing an oil cooler are shown below:

Example 1: Golf 5 with 1.6 Motor

• 55, - Euro material costs oil cooler
• + 130, - Euro work performance
• approx. 260, - Euro total costs including liquids around

Example 2: Mercedes W212

• 350, - Euro material costs oil cooler
• + 550, - Euro approx. 6 working hours
• = 1000, - Euro total costs including liquids

Example 3: BMW 550i

• In this example we have a worst case scenario in which the entire motor has to be replaced. The total cost is around 2000 euros.

TIPP: If your vehicle is less than five years old and has a few kilometers on it, you can submit an application for goodwill to the vehicle manufacturer or car dealer. Especially if the series in which the vehicle falls has had problems with the oil cooler more often.

Replace the oil cooler yourself?

In many cases, replacing the oil cooler is not difficult in principle. A distinction has to be made between series oil coolers and retrofit coolers. The latter can often be removed in just a few simple steps. As already mentioned above, series oil coolers are often integrated in a housing box with a water cooler and / or air conditioning cooler. Removal is then much more difficult and often requires special tools.

various DIY tutorials for changing the oil cooler

Of course that had not happened yet!

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