187° LS Engine Thermostat with Seal
45687
The 187° LS Engine Thermostat with Seal is a reliable choice for most GM LS cooling systems, providing a balanced operating temperature for street, off-road, and performance applications. Manufactured to OEM-style specifications from high-quality copper and stainless steel components, this thermostat is built to provide consistent temperature control in demanding cooling system conditions.
The 187°F temperature rating allows the engine to reach operating temperature efficiently while still providing a practical margin for LS swaps, rock crawlers, trail rigs, race vehicles, and custom cooling systems. An integrated air relief valve helps release trapped air during filling and warm-up, while the included seal provides the components needed for installation.
This thermostat is compatible with the WA01000LS -16 LS Thermostat Housing, WA01000LT -16 LT Thermostat Housing, and WA01001LS -20 LS Thermostat Housing.
Includes:
- (1) 187°F LS Engine Thermostat
- (1) Thermostat Gasket / Seal
Specifications
| Specification | Details |
|---|---|
| Product Type | Engine Coolant Thermostat |
| Engine Platform | GM LS |
| Temperature Rating | 187°F / 86°C |
| Material | Copper and Stainless Steel |
| Flange Thickness | 1/16" / 1 mm |
| Flange Diameter | 2-1/8" / 37 mm |
| Bypass Flange Diameter | 37 mm |
| Overall Height | 2-9/16" / 65 mm |
| Height Between Flanges | 1-13/16" |
| Air Relief Valve | Yes |
| Jiggle Pin | Yes |
| Seal Included | Yes |
Fitment
Compatible Applications:
- GM LS1 engines
- GM LS2 engines
- GM LS3 engines
- GM LS6 engines
- GM LQ4 and LQ9 engines
- GM LM7 and 5.3L LS-based engines
- LS engine swaps
- Custom -16 AN and -20 AN cooling systems
Compatible WOD Thermostat Housings:
- WA01000LS -16 LS Thermostat Housing
- WA01000LT -16 LT Thermostat Housing
- WA01001LS -20 LS Thermostat Housing
Fitment Notes:
- Designed for GM LS-based engine cooling systems.
- Verify flange diameter, thermostat height, bypass flange dimensions, and housing compatibility before installation.
- Custom thermostat housings may use different thermostat dimensions even when designed for an LS engine.
- Inspect the sealing surface and thermostat housing before installation.
- Install the air relief valve in the proper orientation based on the cooling system layout.
FAQ
Why choose a 187°F thermostat for an LS engine?
A 187°F thermostat is a strong all-around choice for most LS swaps and performance vehicles. It allows the engine to warm up properly while providing a slightly lower opening temperature than many factory applications, making it well suited for off-road vehicles, street-driven swaps, and custom cooling systems.
Does a lower-temperature thermostat increase cooling capacity?
No. A thermostat controls when coolant begins circulating through the radiator, but it does not increase the radiator's ability to remove heat. Cooling capacity still depends on radiator size, coolant flow, fan performance, shroud design, airflow, and the overall condition of the system.
What does the air relief valve do?
The integrated jiggle pin allows trapped air to pass through the thermostat during filling and warm-up. This can make the cooling system easier to bleed and helps reduce the risk of air pockets around the thermostat and engine coolant passages.
Why is the included seal important?
The thermostat seal prevents coolant from bypassing the housing connection. Replacing the seal whenever the thermostat is serviced helps reduce the risk of leaks and improper coolant flow.
Will a 187°F thermostat prevent overheating?
A thermostat can help regulate normal operating temperature, but it cannot correct an undersized radiator, weak fan, restricted coolant flow, trapped air, poor shroud design, or other cooling system problems. Persistent overheating should be diagnosed as a complete system issue.
What should be checked during installation?
Confirm thermostat orientation, housing dimensions, seal placement, coolant level, and air bleeding. After installation, inspect for leaks and verify that the engine reaches and maintains a stable operating temperature.
