URO 078121121J Engine Coolant Thermostat Housing

Engine Coolant Thermostat Housing for Audi and Volkswagen

This URO engine coolant thermostat housing is built for direct replacement on select Audi and Volkswagen applications. It is manufactured to OE dimensions for straightforward bolt-on installation and secure hose connections, with a die cast aluminum body that helps resist flange warping and cracking.

Part number 078121121J is used on a range of Audi A4, A6, S4, Cabriolet, 90, and Volkswagen Passat models with aluminum housing and stainless steel water tube configurations.

Key Features

• Die cast aluminum construction with a silver finish
• OE-style dimensions for accurate fitment and hose alignment
• Outlet port diameter: 31.9 mm
• Inlet port diameter: 66.7 mm
• Bolt hole center to bolt hole center: 81.79 mm
• Flange thickness: 10.8 mm
• Height: 30.6 mm
• Includes temperature sensor ports where applicable
• Gasket or seal not included
• 24 month unlimited mileage warranty

Detailed Description

URO part number 078121121J is an engine coolant thermostat housing engineered for direct replacement in select Audi and Volkswagen cooling systems. The die cast aluminum housing is intended to maintain dimensional stability at the flange and connection points, helping preserve reliable sealing and hose attachment under normal operating temperatures. This makes it a practical choice for Audi A4, Audi A6, Audi S4, Audi Cabriolet, Audi 90, and Volkswagen Passat thermostat housing replacement service.

This thermostat housing cross-references Beck/Arnley 143-0709 for the same application. It is a direct-fit OE-style replacement for vehicles that use aluminum housing with stainless steel water tubes, including 1996-2001 Audi A4 and A4 Quattro, 1995-2000 Audi A6 and A6 Quattro, and 1998-2000 Volkswagen Passat. The part number 078121121J also applies to select 2001 Audi A6, 2001 Audi A6 Quattro, and 2001 Volkswagen Passat production ranges noted in the fitment data.

What It Helps Address

• Coolant leakage from a warped or cracked thermostat housing flange
• Loose or unreliable hose connection points at the cooling system housing
• Fitment issues caused by worn or distorted original housing dimensions
• Temperature sensor port replacement needs where applicable
• Cooling system service on Audi and Volkswagen models with aluminum housing and stainless steel water tubes

Installation Notes and Tips

Verify the original housing style, port layout, and production date range before installation. This housing does not include a gasket or seal, so the sealing components should be matched to the vehicle application during service. Confirm hose routing, sensor port usage, and bolt-hole alignment before final tightening to help ensure a proper seal on Audi A4, Audi A6, and Volkswagen Passat cooling system repairs.

Quality Assurance

URO manufactures this thermostat housing to OE dimensions for dependable fitment and consistent hose connection geometry. The die cast aluminum construction is selected to resist flange warping and cracking, and the part is backed by a 24 month unlimited mileage warranty.