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Genuine GM Engine Coolant Thermostat (Part #12680457) – 6.6L Duramax L5P
This is the genuine GM / ACDelco OE 180°F (82°C) engine coolant thermostat for 2017–2026 Chevrolet Silverado and GMC Sierra 2500HD/3500HD trucks equipped with the 6.6L Duramax L5P diesel (also fits select 2019+ Silverado 4500/5500/6500 HD medium-duty models).
Function & Purpose
The thermostat precisely controls coolant flow to the radiator, allowing the engine to reach and maintain optimal operating temperature quickly. This improves fuel efficiency, reduces emissions, provides faster cabin heat, and protects the engine from overheating—especially important during heavy towing, idling, or extreme conditions common with Duramax diesels.
On the L5P Duramax, this is the 180°F (rear/firewall-side) thermostat in the dual-thermostat housing (the front/radiator-side thermostat is typically the 185°F unit).
Key Features & Specifications
- Genuine GM / ACDelco OE quality — Manufactured to exact GM specifications for fit, form, and function
- Start-to-open temperature: 82°C / 179.6°F (commonly referred to as the 180°F thermostat)
- Construction: Stainless steel with jiggle pin weep hole for proper air bleeding
- Direct-fit replacement for the original equipment thermostat
- Dimensions: Approx. 1.97" height × 1.259" sealing flange diameter
- Note: Gasket/seal and thermostat housing sold separately (common replacement practice is to replace both thermostats and gaskets together)
Why Choose Genuine GM?
- Same performance and durability as the factory-installed part
- Ensures proper engine warm-up and cooling system balance in the dual-thermostat L5P design
- Helps prevent common issues like overheating, poor heat output, or diagnostic trouble codes related to coolant temperature (e.g., P01F0)
Recommended Service Tip: When replacing thermostats on an L5P Duramax, it is best practice to replace both the front and rear thermostats at the same time, along with fresh gaskets and coolant, for balanced cooling performance and longevity.
Vehicle Compatibility (confirm with VIN for exact fit):
- 2017–2026 Chevrolet Silverado 2500 HD & 3500 HD (6.6L Duramax L5P)
- 2017–2026 GMC Sierra 2500 HD & 3500 HD (6.6L Duramax L5P)
- Select 2019–2025 Chevrolet Silverado 4500/5500/6500 HD models
This is a non-reusable part (replace, do not reinstall). Always use the correct Dex-Cool or equivalent coolant and follow proper bleeding procedures after installation.
Genuine GM Engine Coolant Thermostat (Part #12680457) – 6.6L Duramax L5P
This is the genuine GM / ACDelco OE 180°F (82°C) engine coolant thermostat for 2017–2026 Chevrolet Silverado and GMC Sierra 2500HD/3500HD trucks equipped with the 6.6L Duramax L5P diesel (also fits select 2019+ Silverado 4500/5500/6500 HD medium-duty models).
Function & Purpose
The thermostat precisely controls coolant flow to the radiator, allowing the engine to reach and maintain optimal operating temperature quickly. This improves fuel efficiency, reduces emissions, provides faster cabin heat, and protects the engine from overheating—especially important during heavy towing, idling, or extreme conditions common with Duramax diesels.
On the L5P Duramax, this is the 180°F (rear/firewall-side) thermostat in the dual-thermostat housing (the front/radiator-side thermostat is typically the 185°F unit).
Key Features & Specifications
Genuine GM / ACDelco OE quality — Manufactured to exact GM specifications for fit, form, and function
Start-to-open temperature: 82°C / 179.6°F (commonly referred to as the 180°F thermostat)
Con[...]
Genuine GM Engine Coolant Thermostat (Part #12680457) – 6.6L Duramax L5P
This is the genuine GM / ACDelco OE 180°F (82°C) engine coolant thermostat for 2017–2026 Chevrolet Silverado and GMC Sierra 2500HD/3500HD trucks equipped with the 6.6L Duramax L5P diesel (also fits select 2019+ Silverado 4500/5500/6500 HD medium-duty models).
Function & Purpose
The thermostat precisely controls coolant flow to the radiator, allowing the engine to reach and maintain optimal operating temperature quickly. This improves fuel efficiency, reduces emissions, provides faster cabin heat, and protects the engine from overheating—especially important during heavy towing, idling, or extreme conditions common with Duramax diesels.
On the L5P Duramax, this is the 180°F (rear/firewall-side) thermostat in the dual-thermostat housing (the front/radiator-side thermostat is typically the 185°F unit).
Key Features & Specifications
- Genuine GM / ACDelco OE quality — Manufactured to exact GM specifications for fit, form, and function
- Start-to-open temperature: 82°C / 179.6°F (commonly referred to as the 180°F thermostat)
- Construction: Stainless steel with jiggle pin weep hole for proper air bleeding
- Direct-fit replacement for the original equipment thermostat
- Dimensions: Approx. 1.97" height × 1.259" sealing flange diameter
- Note: Gasket/seal and thermostat housing sold separately (common replacement practice is to replace both thermostats and gaskets together)
Why Choose Genuine GM?
- Same performance and durability as the factory-installed part
- Ensures proper engine warm-up and cooling system balance in the dual-thermostat L5P design
- Helps prevent common issues like overheating, poor heat output, or diagnostic trouble codes related to coolant temperature (e.g., P01F0)
Recommended Service Tip: When replacing thermostats on an L5P Duramax, it is best practice to replace both the front and rear thermostats at the same time, along with fresh gaskets and coolant, for balanced cooling performance and longevity.
Vehicle Compatibility (confirm with VIN for exact fit):
- 2017–2026 Chevrolet Silverado 2500 HD & 3500 HD (6.6L Duramax L5P)
- 2017–2026 GMC Sierra 2500 HD & 3500 HD (6.6L Duramax L5P)
- Select 2019–2025 Chevrolet Silverado 4500/5500/6500 HD models
This is a non-reusable part (replace, do not reinstall). Always use the correct Dex-Cool or equivalent coolant and follow proper bleeding procedures after installation.