Recently at Auto Studio, an Audi A4 was brought in after the customer experienced an intermittent over-temperature warning on the dash, was regularly topping up coolant and found milky coloured oil.

Symptoms:

• Milky oil
• Overheating
• Warning lights on the dash
• Coolant consumption

 What can cause a vehicle to have milky oil?

This occurs when the cooling system is able to mix with the engine oil through the head gasket or the engine oil cooler. In this case it was an internal failure with the engine oil cooler that allowed the coolant to enter the engine oil galleries. When this occurs it turns the oil a milky colour and becomes very thick causing blockages, which reduces lubrication of the engine & increases the temperature.

How to fix a car with milky oil?

After identifying the problem the contaminated oil was drained and a new oil cooler was fitted. The oil filter and oil were changed and an oil flush was added the engine to aid in removing the contaminated oil. The vehicle was brought up to operating temperature & the oil was drained. This process is to be repeated until the system is free of the contaminated oil. Once the system is free of the contamination the oil and filter were replaced.

Figure 1 shows the milky residue drained from the oil pan.