Mishimoto MMTS-CHV-01DH High Temp Thermostat 2001-2016 Chevy GMC 6.6L Duramax

Vehicle Fitment

• 2001-2016 Chevrolet Silverado 2500HD (6.6L Duramax - LB7, LLY, LBZ, LMM, LML)
• 2001-2016 Chevrolet Silverado 3500HD (6.6L Duramax - LB7, LLY, LBZ, LMM, LML)
• 2001-2016 GMC Sierra 2500HD (6.6L Duramax - LB7, LLY, LBZ, LMM, LML)
• 2001-2016 GMC Sierra 3500HD (6.6L Duramax - LB7, LLY, LBZ, LMM, LML)

Fitment Notes

• This is the high-temperature thermostat set - activates at a higher temperature than OEM, designed for cold climate operation where the engine has difficulty reaching or maintaining full operating temperature. This is the opposite of a low-temperature or racing thermostat. See MMTS-CHV-01DL for the low-temperature (colder-opening) set.
• Set of 2 thermostats: one 185°F thermostat and one 191°F thermostat. The Duramax cooling system uses two thermostats and both are included in this kit.
• Gaskets are not included. Verify the condition of existing thermostat housing gaskets and source replacements as needed before installation.
• Direct-fit replacement - fits the stock thermostat housing on all 6.6L Duramax variants from 2001-2016 (LB7 through LML) with no modification required.
• Installation difficulty rated Easy.

Features

• High-temperature thermostat set (185°F + 191°F) engineered specifically for the 6.6L Duramax - opens at a higher temperature than the OEM thermostats, keeping coolant circulating within the engine longer and delaying flow to the radiator, which allows the engine to reach full operating temperature faster. Ideal for Duramax owners in cold climates or those who have difficulty getting the engine to proper operating temperature.
• Complete set of 2 thermostats matched to the Duramax's dual-thermostat cooling system architecture - replacing both thermostats simultaneously ensures consistent thermal performance across the full cooling circuit. Mixing old and new thermostats of different calibration can result in uneven or inconsistent coolant flow regulation.
• Built with high-quality wax element construction and digitally calibrated for precise activation at the specified temperatures, ensuring consistent and repeatable opening behavior across heat cycles. Imprecise thermostat activation is a common failure mode on aged thermostats that can cause both under-cooling and over-cooling on the Duramax platform.
• Copper and stainless steel construction provides corrosion resistance and durability in the coolant environment over the service life of the thermostats.
• Direct-fit replacement for the stock thermostats in the existing OEM housing - no modification required and no new housing needed. Works with all 6.6L Duramax variants from 2001-2016 including LB7, LLY, LBZ, LMM, and LML engine codes.
• Backed by the Mishimoto Lifetime Warranty.

Specifications

• Thermostat 1 Opening Temperature: 185°F
• Thermostat 2 Opening Temperature: 191°F
• Type: High-temperature (opens at higher temp than OEM - designed for cold climate)
• Quantity: Set of 2
• Calibration: Digitally calibrated
• Material: Copper / stainless steel
• Gaskets Included: No
• Fitment: Direct-fit, uses stock thermostat housing

Included Components

• 1x 185°F high-temperature thermostat
• 1x 191°F high-temperature thermostat
• Mishimoto Lifetime Warranty

Product Description

The Mishimoto MMTS-CHV-01DH is a high-temperature thermostat set for the 2001-2016 Chevrolet/GMC Silverado and Sierra 2500HD and 3500HD with the 6.6L Duramax turbodiesel, covering the full range of Duramax engine generations from the LB7 through the LML. The Duramax cooling system uses two thermostats operating together, and this kit includes both - one calibrated to open at 185°F and a second at 191°F - as a matched replacement set that ensures consistent coolant flow regulation across the full cooling circuit.

This is a high-temperature thermostat, not a low-temperature racing thermostat. It is engineered for the opposite use case: rather than opening earlier to help a hot-running or modified engine shed heat sooner, this thermostat set opens at a higher temperature than OEM, which keeps coolant circulating within the engine longer and delays it flowing through the radiator. The practical benefit is a faster warmup from cold starts, particularly relevant in cold climates where the Duramax can struggle to reach full operating temperature - especially during light-load city driving, short trips, or in extremely cold ambient conditions. A diesel engine that doesn't reach full operating temperature runs with increased fuel dilution of the oil, reduced combustion efficiency, elevated internal wear, and in some cases, accumulated crankcase moisture - all of which are reduced when the engine warms up faster and maintains a stable operating temperature.

Each thermostat is built with high-quality wax element construction and digitally calibrated for precise opening at the specified temperature, providing consistent and repeatable performance across heat cycles. The thermostats are direct-fit replacements for the stock units in the OEM thermostat housing - no modification required. Note that gaskets are not included; verify the condition of existing housing gaskets and source replacements separately before installation. For Duramax owners in warm climates or running power upgrades who need faster heat shedding, the Mishimoto low-temperature Duramax thermostat set (MMTS-CHV-01DL) is the appropriate complement. Covered by the Mishimoto Lifetime Warranty.