Motorad 304-198 Engine Coolant Thermostat

OE-Style 198°F Thermostat for Audi and Volkswagen

The Motorad Standard 304-198 engine coolant thermostat is built for OE-specified temperature control in select Audi and Volkswagen cooling systems. It uses OEM-quality materials and a copper case with wax compound for quick reaction to coolant temperature changes.

Compatible With 1999-2005 Audi A4, A4 Quattro, A6, and A6 Quattro, plus 1999-2005 Volkswagen Passat applications listed below.

Key Features

• 198°F start-to-open temperature for OE-specified cooling performance
• Copper case and wax compound for rapid response to coolant temperature changes
• Offset design with air relief valve where applicable
• Jiggle pin weep hole included for air bleeding
• OEM-style seals used where applicable
• Standard thermostat design for direct replacement service
• Motorad Standard 304-198 for select Audi and Volkswagen applications

Detailed Product Overview

Motorad Standard line thermostats are OE-style replacement parts focused on factory-correct temperature regulation. The 304-198 is engineered to open at 198°F and maintain stable coolant flow in demanding automotive cooling systems. Its copper case and wax element help the thermostat react quickly as engine temperature changes, supporting consistent warm-up and operating temperature control. This part cross-references DENSO Auto Parts 4090 for the same application.

Fits 2000-2005 Volkswagen Passat, N/A. Fits 2000-2001 Audi A6, N/A. Fits 2000 Audi A4, N/A. Fits 2000 Audi A4 Quattro, N/A. Fits 2000 Audi A6 Quattro, N/A. Fits 1999 Audi A6, N/A. Fits 1999 Audi A6 Quattro, N/A. Fits 1999 Volkswagen Passat, N/A.

Common Cooling System Issues It Can Address

• Engine running cooler or hotter than the specified operating range
• Delayed warm-up after cold starts
• Temperature fluctuation caused by a sticking thermostat
• Coolant flow control problems in the thermostat housing circuit
• Check engine concerns related to coolant temperature regulation

Installation Notes and Tips

Verify the 198°F temperature specification and confirm vehicle fitment by year, make, model, and VIN notes before installation. Inspect the sealing surfaces, housing condition, and coolant quality during service. This thermostat includes a jiggle pin weep hole and uses OEM-style sealing features where applicable, but a gasket or seal is not included.

Quality Assurance

Motorad manufactures this thermostat with OEM-quality materials and processes as an OE supplier, using specifications intended to meet factory cooling-system requirements. The Standard line focuses on direct-fit replacement parts for routine cooling system service. Motorad 304-198 is built for select Audi and Volkswagen applications listed above.