Gates 33957 Engine Coolant Thermostat

Heavy-Duty Engine Cooling Control

The Gates Heavy-Duty Thermostat 33957 is an engine coolant thermostat built for demanding truck, bus, tractor, and heavy equipment cooling systems. It uses steel, brass, and copper construction to handle the vibration and harshness common in heavy-duty service, while maintaining stable coolant flow control at a 190°F opening temperature.

For fleet maintenance and repair work on applications such as Ford F-Series and Chevrolet/GMC truck platforms, this thermostat supports consistent engine warm-up and temperature regulation. Gates 33957 is a bottom by-pass design with a 2.21 in valve diameter and a 1.62 in by-pass flange diameter.

Gates Heavy-Duty Thermostat Features

• Part number: 33957
• Heavy-duty thermostat for engine coolant temperature regulation
• Bottom by-pass design for the specified cooling system layout
• 190°F / 88°C start-to-open temperature
• Steel, brass, and copper construction
• Sealing flange outside diameter: 2.94 in
• Height from flange: 2.01 in
• Flange thickness: 0.06 in
• No jiggle pin weep hole
• No installation tool included

Product Line Details

Gates Green Stripe Heavy-Duty Thermostats are part of the brand’s heavy-duty cooling line for commercial and off-highway service. This product line focuses on thermostat performance in environments where heat cycling, vibration, and under-hood stress are part of daily operation.

Detailed Application Overview

Use Gates 33957 when replacing a heavy-duty engine coolant thermostat in a bottom by-pass cooling system that calls for a 190°F opening point. The metal construction and compact flange dimensions support reliable fitment in demanding cooling assemblies, including Ford F-Series and Chevrolet/GMC truck applications where accurate coolant control is important for operating temperature stability.

This part cross-references Motorad 4051-90 for the same application.

What It Helps Address

• Slow engine warm-up caused by a thermostat stuck open
• Overheating from a thermostat that does not open at the correct temperature
• Temperature fluctuation in heavy-duty cooling systems
• Coolant flow issues in bottom by-pass thermostat housings
• Service replacement for worn or corroded thermostat components

Installation Notes and Tips

Verify the thermostat housing design, by-pass configuration, flange dimensions, and opening temperature before installation. Clean the sealing surfaces thoroughly and inspect the housing for corrosion, pitting, or distortion that could affect sealing. Because no gasket quantity is specified, match the required sealing components to the vehicle application and housing design.

Quality Assurance

Gates designs this heavy-duty thermostat for commercial-duty cooling environments where durability and temperature control matter. The steel, brass, and copper construction is selected for service in applications exposed to vibration and harsh operating conditions.