Coolant Thermostat Housing – 021-121-117A The 021-121-117A is a primary cooling system component specifically designed for the Volkswagen 2.8L VR6 engine. This housing serves as the central hub for the thermostat and various coolant sensors. Because the VR6 engine operates at high temperatures and features a compact design, the original plastic housing is prone to warping, "heat-soaking," and developing hairline cracks over time. A failure in this housing typically results in persistent coolant leaks, which can lead to engine overheating if not addressed. Replacing a brittle or leaking unit with a fresh 021-121-117A ensures a watertight seal for the cooling system, maintaining proper pressure and protecting your VR6 engine from thermal damage. This is a vital part for any high-mileage cooling system refresh. Detailed Vehicle Compatibility Fits 2.8L V6 (VR6) 12-valve engines. VW Corrado (SLC): 1992, 1993, 1994, 1995 VW EuroVan (Camper): 1997, 1998, 1999, 2000 VW Golf (GTI VR6): 1995, 1996, 1997, 1998 VW Jetta (GLX): 1994, 1995, 1996, 1997, 1998, 1999 VW Passat (GLX): 1993, 1994, 1995, 1996, 1997 Product Highlights & Features Direct OEM Replacement: Manufactured to the exact dimensions of the original factory part for a seamless fit on the cylinder head. Reinforced Material: Constructed from high-quality composite plastic designed to withstand constant thermal cycling and cooling system pressure. Sensor Port Integrated: Features the correct provisions for coolant temperature sensors (ECT) and the thermostat flange. Essential Maintenance: Prevents the most common cause of "mystery" coolant loss on the 12v VR6 platform. Technical Specifications Part Number: 021-121-117A Material: Reinforced Plastic / Composite Engine Displacement: 2.8L V6 (12-Valve VR6) Application: Thermostat / Cooling Water Outlet Installation & Maintenance Tips Replace the Seals: Always use new O-rings and gaskets when installing this housing. Reusing old, flattened seals is the most common cause of leaks immediately following a replacement. Inspect the "Crack Pipe": While the thermostat housing is removed, it is the best time to inspect the plastic coolant distribution pipe (commonly called the "crack pipe"). These often fail together, and replacing them simultaneously saves hours of labor. Torque Carefully: The mounting bolts for this housing thread into the aluminum cylinder head. Use a torque wrench to meet factory specifications, as over-tightening can easily strip the threads or crack the new plastic housing. System Bleed: After installation, ensure you properly bleed the air out of the cooling system. VR6 engines are known for trapping air pockets, which can cause erratic temperature readings and localized hot spots. 021121117A
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