1J0121403B Engine Parts Expansion Tank & Replacement Parts

The 1J0121403B is an engine coolant expansion tank used in several Volkswagen and Audi models, primarily those from the early 2000s. Its main function is to store excess coolant that expands as the engine heats up and to maintain the optimal coolant pressure in the system.

Key features:

• Material: Typically made from durable plastic, resistant to heat and pressure.
• Capacity: Designed to hold a specific amount of coolant to ensure efficient operation of the cooling system.
• Pressure Relief: It usually integrates a pressure cap that allows for the release of excess pressure, preventing damage to the radiator or other parts.
• Sensor: Some versions include a level sensor to monitor coolant levels and provide warnings if low.
• Compatibility: Primarily fits certain VW and Audi vehicles, often found in models like the VW Golf, Passat, Audi A3, and others with similar cooling systems.

It’s important to replace this component if it shows signs of cracking, leaks, or damage, as a faulty expansion tank can lead to coolant loss, overheating, or engine damage.

Would you like further details on its installation or any specific part compatibility?