Sierra 18-3539 140 Degree Thermostat Kit for Closed Cooling Systems, Replaces 875779

The Sierra 18-3539 is a 140 degree thermostat kit built for closed cooling systems, supplying a marine engine's cooling circuit with a factory-style thermostat that opens at the correct temperature to keep the engine running in its proper operating range. Running an engine without the correct thermostat, or with a unit that has failed open or closed, can lead to overheating or the engine never reaching efficient operating temperature, so replacing a worn or incorrect thermostat with the properly rated 140 degree unit is a routine but important part of closed cooling system maintenance.

This kit includes the sealing ring needed for installation, so the thermostat housing can be resealed at the same time the thermostat itself is replaced, reducing the chance of a coolant leak from an old or hardened gasket surface. The 18-3539 is designed as a direct replacement for engines that originally used a 140 degree thermostat in a closed cooling configuration.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3539
• Product Type: Thermostat Kit
• Temperature Rating: 140 degrees
• System Type: Closed Cooling System
• Includes: Sealing ring
• Product Dimensions: 2.75 x 3.63 x 2.5 inches
• Weight: 0.2 pounds
• UPC: 808282265854

Fitment

• Designed for closed cooling systems specifying a 140 degree thermostat

Replaces (OEM)

• 875779

Frequently Asked Questions

What temperature does the Sierra 18-3539 thermostat open at? The Sierra 18-3539 is rated at 140 degrees, meaning it opens at that temperature to regulate coolant flow in a closed cooling system.

Does this kit include the sealing ring? Yes, the 18-3539 thermostat kit includes the sealing ring needed to reseal the thermostat housing during installation.

What OEM part numbers does the Sierra 18-3539 replace? The 18-3539 replaces OEM part number 875779.

Is the 18-3539 a complete kit or just the thermostat? It is a complete kit consisting of the 140 degree thermostat and a sealing ring, not just the thermostat alone.

What type of cooling system is the 18-3539 designed for? This thermostat kit is designed for closed cooling systems, where the correct 140 degree thermostat is required for proper temperature regulation.

How much does the 18-3539 thermostat kit weigh? The Sierra 18-3539 weighs 0.2 pounds.

What are the dimensions of the 18-3539 thermostat kit? The kit measures 2.75 x 3.63 x 2.5 inches.

Is the Sierra 18-3539 a genuine aftermarket replacement part? Yes, the 18-3539 is manufactured by Sierra as a direct replacement thermostat kit, cross-referenced to OEM number 875779.

Why does my engine need the correct thermostat temperature rating? Installing a thermostat with the wrong temperature rating, instead of the 140 degree unit specified for the 18-3539 application, can cause the engine to overheat or run below its proper operating temperature.

What is the UPC for the Sierra 18-3539 thermostat kit? The UPC for the Sierra 18-3539 thermostat kit is 808282265854.