What Causes Oil in the Water of a Passat?
2 Answers
The reasons for oil in the water of a Passat are as follows: Blown Head Gasket: When the head gasket is damaged, it connects the oil passage with the water passage. Since the oil pressure is higher than the coolant pressure, the oil enters the water passage and then the radiator. You can observe air bubbles escaping from the surface of the radiator coolant. After shutting down the engine, the coolant will flow into the oil passage and then into the oil pan. Cracked Cylinder Liner: Due to the high fuel pressure inside the cylinder, engine oil and diesel are "squeezed" into the coolant through cracks in the cylinder liner under high pressure. Observing the coolant surface, the movement of air bubbles is very intense. Oil Cooler Malfunction: During assembly or manufacturing of the oil cooler, cracks in the cooling tubes, poor welding, or freezing and cracking of the cooling tubes due to leftover coolant in winter can cause oil to enter the coolant. If you observe the radiator coolant surface, it generally appears calm.
I've encountered this situation before, especially with the Passat model. When engine oil mixes into the coolant, it's most likely due to a faulty engine head gasket seal allowing oil to leak in. The head gasket is located between the engine block and cylinder head, serving to seal the combustion chamber and prevent the mixing of water and oil. If it becomes damaged due to engine overheating, aging, or prolonged high-load operation, engine oil can flow into the cooling system. Additionally, internal leakage or corrosion in the oil cooler can also cause this phenomenon. Once oil-like substances are detected in the coolant, it indicates that both the lubrication and cooling systems are affected. Continuing to drive may lead to more severe problems, such as engine overheating damaging internal components. It's advisable to stop the vehicle immediately and avoid forced driving. Seek professional repair services as soon as possible to inspect the head gasket, replace sealing components, and thoroughly clean the entire cooling system to prevent residual oil from clogging the pipes.
