Gates 33857S Engine Coolant Thermostat

Reliable Cooling Control for Subaru Vehicles

The Gates Premium Thermostat 33857S is engineered to maintain optimal engine temperature for Subaru models including Baja, Forester, Impreza, Legacy, Outback, WRX, and WRX STI. Designed with durable stainless steel and copper materials, this engine coolant thermostat ensures consistent performance and longevity.

• Constructed from stainless steel and copper for durability
• Reverse poppet design for precise temperature regulation
• Start to open temperature at 170°F (77°C) for accurate coolant flow
• Sealing flange outside diameter of 2.2 inches for secure fit
• Compact height of 1.61 inches with 0.9 inch height between flanges
• No jiggle pin or weep hole, reducing potential leak points
• Compatible with multiple Subaru models for direct replacement

About the Gates Premium Thermostat Line

The Premium Thermostat line by Gates focuses on delivering reliable engine temperature control through high-quality materials and precise engineering. This line is designed to meet or exceed OEM specifications, providing consistent opening temperatures and robust sealing without the need for additional gaskets or jiggle pins. The 33857S model exemplifies these qualities, offering a reverse poppet design that enhances coolant flow management in Subaru engines.

Product Details and Specifications

The Gates 33857S thermostat features a reverse poppet design, which improves the response time to temperature changes, helping maintain engine efficiency. Its stainless steel and copper construction resists corrosion and wear, extending service life. The thermostat opens at 170°F (77°C), ensuring the engine reaches optimal operating temperature before coolant circulation begins. With a sealing flange diameter of 2.2 inches and a total height of 1.61 inches, it fits securely within the cooling system housing without requiring additional gaskets or seals.

Common Applications and Problem Resolution

• Prevents engine overheating by regulating coolant flow
• Helps avoid poor fuel economy caused by incorrect engine temperature
• Reduces risk of engine damage from thermal stress
• Eliminates coolant leaks associated with worn or damaged thermostats
• Restores proper heating performance in cabin systems

Installation Notes and Tips

This thermostat is designed for direct replacement in compatible Subaru models. No installation tool is included, so using appropriate hand tools and following vehicle-specific service manuals is recommended. Ensure the sealing flange is clean and free of debris before installation to maintain a proper seal. Since this model does not include gaskets or jiggle pins, verify the housing and mating surfaces are in good condition to prevent leaks.

Quality Assurance and Warranty

Gates Premium Thermostats are manufactured to meet strict quality standards, ensuring reliable operation under normal driving conditions. While specific warranty details for part number 33857S should be confirmed with the parts provider, Gates typically offers coverage against manufacturing defects. Using this thermostat helps maintain the integrity of the Subaru cooling system and supports engine longevity.