BMW X4 radiator

The part is used in the engine cooling and lubricating systems, hydraulic power steering, and transmission. It is designed to reduce the temperature of coolant or oil. The radiator consists of two tanks and a core between them. The core is made of many tubes through which the fluid flows. They are soldered to the plate fins or corrugated fins that come into contact with air and ensure heat dissipation. Cooling is achieved due to on-coming air flow during car movement. Sometimes a fan is used additionally.

When you start a cold engine, especially in cold weather, a thermostat valve is closed, thus the coolant flows in a small circle bypassing the radiator. This helps the engine to reach its operating temperature faster. This explains why the lower hose is cold – heated coolant doesn’t flow through it.

As soon as the engine reaches its operating temperature, the thermostat valve opens fully or partially. Hot coolant flows through the radiator, and the lower pipe should become warm. If this doesn’t happen, your car may have the following problems:

• clogged hoses;
• airlocks in the hoses;
• water pump failure;
• stuck thermostat.

Visit a car service station for thorough diagnostics.

In most cases, airlocks are caused by:

• Stuck intake valve of the radiator cap or expansion reservoir cap.
• Small cracks on the hoses, leaky joints, a loose-fitting expansion reservoir cap.
• Boiling of coolant, which comes with air emission.
• Damaged cylinder head gasket, which results in the ingress of exhaust gases into the system.
• Incorrect bleeding of the unit after repair works.