058 121 133B – Cylinder Head Coolant Flange

Description

The 058 121 133B coolant flange serves as a critical connection point at the rear of the engine block on select 1.8L turbocharged engines. This plastic outlet directs hot coolant from the cylinder head back toward the radiator and heater core circuits. Because it is located at a high-stress point in the cooling system, it is frequently exposed to extreme thermal fluctuations.

The factory plastic material can gradually warp or become brittle over time, making this flange a common point of failure. Replacing a leaking or aging unit is vital to maintaining system pressure and preventing air from entering the cooling circuit, which can lead to localized engine hotspots.

Why the 058 121 133B Coolant Flange Matters

Maintaining the integrity of the 058 121 133B coolant flange is necessary for consistent engine cooling. Aluminum cylinder heads on 1.8T engines require precise temperature regulation to prevent structural damage. A hairline crack in the flange can allow coolant to seep onto the transmission housing or exhaust components, often evaporating before it hits the ground.

By choosing a high-quality replacement with heat-resistant properties, you ensure the flange mounting surface remains flat against the cylinder head. This supports a reliable seal and prevents the sudden loss of coolant that could lead to roadside overheating.

Signs Your Coolant Flange Needs Replacing

Inspect the rear of the cylinder head if you notice these symptoms:

• Pink or white crusty residue (coolant scale) around the flange mounting area.

• Drops of coolant on the driveway located toward the back of the engine bay.

• The distinct sweet smell of burning coolant after the engine reaches operating temperature.

• Repeated low coolant warnings on the instrument cluster without visible radiator leaks.

• Coolant pooling on top of the transmission casing.

Key Features

• OE Part Number: 058 121 133B

• Direct Replacement: Manufactured to OE dimensions for a secure, bolt-on fit.

• Includes O-Ring: Comes with the necessary sealing gasket to prevent leaks.

• Compatibility: Optimized for the 1.8L 20-valve turbocharged (1.8T) engine platform.

• Material Durability: High-grade materials designed for long-term heat resistance.

• Service Note: Check your temperature sensor configuration; some applications may requires an additional plug (ES253103).

Service Notes

Always verify fitment by VIN before ordering. When replacing the 058 121 133B coolant flange, ensure the engine is completely cool to avoid pressure-related injury. Clean the aluminum cylinder head surface thoroughly with a non-abrasive pad to remove any old seal residue. Corroded or pitted mating surfaces may require careful cleaning to ensure the new O-ring seats effectively.

Avoid over-tightening the mounting bolts, which can crack the plastic housing. Refill the system with the manufacturer-specified G12/G13 coolant and perform a comprehensive bleed procedure to remove air pockets from the cylinder head.

Compatibility & Applications

Always verify fitment by VIN before ordering.

Cross Reference Numbers

• 058 121 133B

• 058121133B

• 058-121-133-B

• 058 121 133 B

• V10-0283

• Febi 14646

Additional information