A stuck thermostat on a Duramax rarely picks a convenient time. The gauge climbs on a highway pull, the coolant temp swings wildly, and suddenly a Saturday morning is spent chasing parts that may or may not fit your VIN. Most owners can swap a thermostat in a garage with basic hand tools, but the wrong temperature rating, a missing gasket, or a housing that doesn’t match the model year turns a 90-minute job into a weekend of returns.
This shortlist focuses on thermostats and thermostat housings that surface in the Duramax conversation: Motorcraft factory-style units for the 6.6L platform, GM/ACDelco OE-spec coolant thermostats for related GM 3.6L and 6.0L applications, an Edelbrock high-flow option for tuned setups, and a complete housing assembly for owners who want the thermostat and water inlet in one part. Each entry is matched to a specific truck, year range, and use case so you can match the right component before you click.
A Fast Comparison Of The Options
Motorcraft RT1201 Thermostat
GM Genuine Parts 131-71 Engine Coolant Thermostat
GM Genuine Parts 131-163 Thermostat with Gasket
GM Genuine Parts 131-131 Thermostat with Gasket
GM Genuine Parts 131-151 Thermostat with Seal
GM Genuine Parts 131-87 Engine Coolant Thermostat
Edelbrock 8604 High Flow Thermostat (180 Deg)
GM Genuine Parts 15-11006 Thermostat and Housing Assembly
MILIPARTS Thermostat Housing for 3.6L GM
Motorcraft RT-1169 Thermostat 190F
Meet The Standout Selections
The Motorcraft RT1201 is the factory-spec replacement that Ford and many diesel service centers reach for first. Built as a direct-fit part for a wide range of Ford and Lincoln applications, it carries the same temperature calibration as the original, which matters on a 6.6L Duramax that runs hotter under load than a gas engine. For most owners, that means predictable warm-up time, stable operating temperature, and a thermostat that won’t drift open after a few thousand miles.
You drop the RT1201 into the housing, bleed the air out of the cooling system, and your gauge returns to its usual spot. It’s a small part, but a failing one shows up fast in coolant behavior, heater output, and fuel economy. Compared with the GM OE thermostats further down this list, the RT1201 is the right call for Ford-built diesel platforms and any owner who prefers a Motorcraft-spec part.
What Makes Sense
- Factory-style temperature rating that matches OE behavior on the Duramax platform
- Vehicle-specific fit, which trims guesswork on gasket style and housing depth
- Compact stainless-style construction that resists wear from long coolant cycles
- Common sizing keeps the swap straightforward for a home garage setup
Things To Consider
- You may need to source a new gasket or O-ring separately, since this listing is the thermostat only
- Third-party sellers vary on packaging, so ordering from a trusted fulfillment path matters
Who It Suits Best
Duramax 6.6L owners who want a Motorcraft-spec thermostat that matches original operating behavior and a familiar swap procedure.
Look Elsewhere When
The Motorcraft RT-1169 is a better match if you specifically need a 190F / 88C rated unit for a particular model-year build.
The 131-71 is a GM-recommended replacement that mirrors the original component on a long list of GM trucks and SUVs. It’s a temperature-controlled valve (the small spring-loaded disc that opens and closes with coolant heat) seated in the coolant outlet, and it does the simple job of letting engine coolant move through the radiator only when the block is warm enough. That single function decides whether your heater works in January and whether your cooling fan runs itself ragged.
For most owners, this is the safe pick. It comes from the same engineering pipeline as the part on the assembly line, which usually means the disc opens at the right temperature and the seat seals cleanly. Compared with the Motorcraft RT1201 above, the 131-71 is the obvious choice on a GM platform rather than a Ford one.
Strong Points
- OE-spec opening temperature keeps the gauge reading where the manufacturer intended
- Direct-fit design avoids the “close enough” clearance issues that aftermarket valves sometimes have
- Stable seat material that resists pitting from extended coolant life
- Widely stocked across auto parts channels for quick turnaround
Worth Noting
- Seal and gasket are not always included, so plan to pull the old one or buy separately
- Best results come from a full coolant bleed after the swap, which adds time on first start
At A Glance
Right Fit For
GM truck and SUV owners doing a routine thermostat swap who want the same temperature calibration the truck left the factory with.
Skip It When
The GM Genuine Parts 15-11006 assembly makes more sense if your housing is cracked or you want a thermostat and water inlet replaced together.
The 131-163 is the kit version of the 131-71 above: same OE-spec thermostat, but it ships with a fresh gasket so you don’t open the housing and discover a torn ring of paper at the bench. For most home mechanics, that single inclusion is the difference between a one-trip job and a follow-up run to the parts store. The thermostat itself does the same work, regulating coolant flow so the block reaches and holds its designed operating temperature.
You install the assembly, torque the housing bolts to spec, and refill. The kit format also makes it easier to confirm the part number against your VIN before the cover comes off. Compared with aftermarket-only thermostats in this price range, the included gasket reduces the small but real risk of a weeping seal on the first heat cycle.
Useful Highlights
- Bundled gasket saves a second parts run and speeds up the swap
- OE-spec temperature calibration suited to GM diesel and gas platforms
- Clean packaging that protects the sealing surfaces in shipping
- Strong fit for owners who service their own trucks each season
Room For Improvement
- Gasket thickness is matched to OE housings, so non-original aftermarket housings may need a different seal
- Documentation in the box is minimal, so rely on a model-specific guide for torque values
Best Suited To
Garage and weekend DIYers who want the thermostat and matching seal in one box and prefer not to chase a second order.
Consider Something Else When
The GM Genuine Parts 131-131 is a similar kit option worth checking if your specific model year is matched to that part number.
The 131-131 sits in the same family as the 131-163 above, with the same OE-spec thermostat-and-gasket format. The difference is the underlying part number, which matches a different set of GM applications. If you confirmed the 97241130 thermostat against your VIN, this is the kit that lines up with that number and ships with the seal already in the box.
It functions the same way any coolant thermostat does: it stays closed while the block warms, then cracks open at the rated temperature to let coolant circulate through the radiator. From a feel standpoint, you won’t notice the difference between this and the 131-163 once installed. What matters is fit, and that comes down to the number on the listing matching the number in your service manual.
Reasons It Performs
- Matched gasket and thermostat for a clean one-piece install
- OE-spec opening temperature for stable gauge behavior
- Compact, well-toleranced disc that resists sticking over time
- Solid choice for routine seasonal service on a GM platform
Trade Offs
- Only worth the cost when the part number matches your specific application
- Coolant still needs a full bleed and refill after the install
Made For
Owners of GM trucks and SUVs whose service manual points to the 131-131 part number for the thermostat and seal.
Not Your Match When
Switch to the GM Genuine Parts 131-87 if you service a platform that calls for the 12514334 thermostat instead.
The 131-151 is the kit built for work-truck duty, where thermostats live through long idles, dusty air, and temperature swings that would cook a lesser part. It pairs the OE-style coolant thermostat with a fresh seal, so the housing closes up tight on the first torque. The result is a thermostat that holds its rating and a seal that doesn’t weep after a hot week on the highway.
For owners logging heavy miles, the appeal is straightforward. You’re not chasing a vague temperature drift or dealing with air pockets after the swap. Compared with the 131-163, this is a different fitment list, so confirm your part number before ordering. Once matched, the install is familiar to anyone who has done a coolant thermostat before.
What Stands Out
- Sealed kit design that helps on trucks with long coolant-cycle intervals
- Sturdy disc construction suited to high under-hood temperatures
- Matches OE calibration for predictable warm-up and fan cycling
- Compatible with a wide range of GM truck and SUV applications
Small Caveats
- Box contents are minimal, so keep your housing bolts and coolant on hand before starting
- Some sellers list this under different cross-reference numbers, which can slow the search
Perfect Match For
Tow and work truck owners who want a sealed OE-style kit that holds up under heavy load and extended idle time.
A Better Fit Elsewhere
Look at the Edelbrock 8604 if you’ve raised the operating temperature on a tuned build and want a 180F thermostat with more flow.
The 131-87 is a premium aftermarket-style coolant thermostat from the GM parts catalog, designed as a high-quality replacement for many vehicles still on the road. It uses the same temperature-controlled valve design as the OE units above and slots into the coolant outlet or inlet near the radiator. The practical difference shows up over time: stable operating temperature and a thermostat that doesn’t stick after a long coolant interval.
For owners who want a name-brand part without paying assembly-line OE prices, the 131-87 is often the choice. It’s a common fitment on 6.0L and similar GM platforms, which makes it a useful bench stock option if you service more than one vehicle. Compared with the 131-71, the construction is similar but the application list is different, so the part number is what decides the call.
Real Benefits
- Brand-name construction with consistent opening tolerances
- Suited to many older GM trucks and SUVs still in daily use
- Compact, drop-in fit that mirrors the original housing depth
- Reliable sealing surface that resists wear from coolant chemistry
Honest Caveats
- Packaging may not include a new seal, so plan for a separate gasket or O-ring
- Coolant type and bleed procedure still matter for long-term reliability
Quick Facts
Who Will Love This
Owners of older GM trucks and SUVs with a 6.0L or similar platform who want a familiar thermostat swap that doesn’t break the budget.
Swap It Out When
The Motorcraft RT-1169 is worth a look if your build calls for a 190F thermostat and you prefer a Motorcraft-spec part.
The Edelbrock 8604 is a high-flow thermostat with a 180-degree opening rating, built for engines that move more coolant than a stock application. The 53mm body allows more coolant to pass per minute than a standard OE thermostat, which matters on tuned setups where the block runs hotter or the radiator is being asked to handle more heat. The 180F rating also raises the operating temperature slightly compared with some 195F OE units, which can help reduce detonation risk under boost on a performance build.
For a stock Duramax daily driver, the OE-spec thermostats on this list are usually the better fit. For a truck with a tune, an upgraded radiator, or a higher-flowing water pump, the 8604 is the part that makes those changes work together. It’s a vehicle-specific fit, so confirm the 53mm body matches your housing before ordering.
Everyday Perks
- High-flow design that supports tuned and high-output builds
- 180F rating useful for raising coolant temperature under load
- Sturdy 53mm disc construction from a performance-focused brand
- Made in the United States with consistent quality control
Points To Keep In Mind
- Not the right rating for a stock-calibration daily driver
- Heater output at idle can be slightly delayed on cold mornings
Built With In Mind
Tuned and performance-build owners who want more coolant flow and a higher operating temperature than an OE thermostat provides.
Reach For A Different Pick When
Stay with the Motorcraft RT1201 if your build is stock and you prefer a thermostat that matches the factory temperature curve.
The 15-11006 is a complete thermostat and water inlet housing assembly, which means you’re replacing the housing and the thermostat in one part. For owners whose plastic housing is cracked from age, heat cycling, or a previous over-torque, this is the part that solves both problems at once. The thermostat inside is the same temperature-controlled design used elsewhere in the GM line, so gauge behavior stays predictable after the swap.
The housing also serves as the water inlet connection, so a worn or warped part can leak coolant slowly enough to drop the level between service intervals. A full assembly eliminates that weak point. Compared with the 131-71, this is a bigger job and a higher part cost, but the labor overlap makes it efficient when the housing is already suspect.
Bright Spots
- Combined thermostat and housing cuts the install into one part number
- OE-spec thermostat calibration inside a fresh housing
- Replaces a common failure point on aging GM platforms
- Clean fitment that matches the original coolant routing
Practical Considerations
- Costs more than a thermostat-only replacement
- Coolant loss during the swap is significant, so a full refill and bleed is part of the job
Feature Snapshot
Whose Shelf It Belongs On
Owners dealing with a cracked or leaking thermostat housing who want the thermostat refreshed at the same time.
Where Another Pick Suits Better
The MILIPARTS thermostat housing is a more budget-minded fit if you’re running a 3.6L GM and don’t need the OE-branded assembly.
The MILIPARTS thermostat housing is an aftermarket assembly designed to fit a specific run of 3.6L GM V6 models, including the Buick LaCrosse, Cadillac XT5, Cadillac XT6, GMC Acadia, and Chevrolet Blazer from the late-2010s into the early 2020s. The package includes the thermostat, tube, gasket, and housing, so it covers the common failure mode on these models where the original plastic housing cracks and the thermostat needs attention anyway.
For owners outside the 3.6L V6 community, this part won’t apply, since it does not match a Duramax application. For those who do own one of the listed GM models, it’s a cost-effective way to handle the housing and thermostat in a single order, with the gasket included. The 12678779 cross-reference number is what to confirm against the original part before clicking.
What Helps Most
- Complete kit with thermostat, tube, gasket, and housing
- Fits a defined list of 3.6L GM applications
- Replaces a known weak point on plastic OEM housings
- More accessible than dealer-only OE assemblies
A Few Limitations
- Specific to 3.6L V6 models, not a Duramax fitment
- Aftermarket brand, so longevity depends on coolant chemistry and install care
Who Should Grab It
Owners of 2017-2023 GM vehicles with the 3.6L V6 who need a complete housing and thermostat refresh at a lower cost than the dealer option.
Consider Something Else When
The GM Genuine Parts 15-11006 assembly is the better choice if you prefer the OE-branded housing on a different GM platform.
The Motorcraft RT-1169 carries a 190F / 88C opening rating, which makes it the right OE-spec thermostat for specific Ford diesel applications that call for that temperature rather than the more common 195F rating. Functionally, it does the same job as any coolant thermostat: stays closed while the block warms, then opens to send coolant through the radiator once the rated temperature is reached.
On a Duramax context, this is the part to keep in mind if your service manual points to a 190F rating, since the wrong temperature can affect heater output, gauge behavior, and how the cooling fan cycles. Compared with the RT1201 above, the RT-1169 is the part to choose when that specific 88C rating is the one your build calls for.
The Value In It
- 190F / 88C rating for builds that call for that temperature
- Motorcraft-spec construction for consistent OE-style behavior
- Compact disc design that fits standard Ford-style housings
- Good fit for restoration and OEM-correct service work
Less Ideal Details
- Specific to 190F applications, so not a universal OE replacement
- Third-party seller pricing can vary, so compare total cost before ordering
Whose Shelf It Belongs On
Owners performing OEM-spec service on a build that calls for a 190F / 88C rated thermostat and want a Motorcraft-branded part.
Where A Sibling Pick Shines
The Motorcraft RT1201 is the better everyday call for most Duramax applications that use a 195F rating.
What To Weigh Before Choosing A Coolant Thermostat
A thermostat is a small, cheap part that decides whether the rest of the cooling system works as designed. Getting the right one means matching three things before you click: the temperature rating, the part number, and the housing it fits.
Temperature rating matters because the engine is calibrated around a specific coolant temperature. Pick a thermostat that opens at a different temperature, and the gauge, the fan cycle, the fuel map, and the heater output all shift. Stock Duramax applications usually call for a 195F / 90C unit, while the Motorcraft RT-1169 covers the 190F / 88C builds. Tuned setups sometimes want a higher-rated thermostat like the Edelbrock 8604’s 180F profile, but that’s a deliberate change tied to other cooling upgrades.
Part number match is non-negotiable. GM alone runs dozens of thermostat part numbers across the 6.6L diesel, the 6.0L gas, and the 3.6L V6 family. Cross-referencing the OE number to the listing is the fastest way to avoid a return. The Motorcraft side is simpler, but the same rule applies.
Housing condition is the third factor. A thermostat installed in a cracked plastic housing is a leak waiting to happen. If the housing is showing signs of age, an assembly like the GM 15-11006 or the MILIPARTS housing combines the thermostat with a fresh housing in one part.
Owner profile matters too. Daily drivers benefit from OE-spec parts that preserve original behavior. Tow and work trucks see more heat cycling, so a sealed kit or a robust aftermarket thermostat can be worth the small premium. Tuned builds live in a different category, where a high-flow thermostat that supports the rest of the cooling system makes more sense than a stock replacement.
Common Pitfalls And When The Premium Pays Off
Where Shoppers Go Wrong
The most common mistake is matching by brand instead of by part number. A Motorcraft thermostat and a GM thermostat look similar in photos, but they fit different housings and often open at different temperatures. Always cross-check the OE number before ordering. The second pitfall is forgetting the gasket. Thermostat-only listings rarely include a fresh seal, which means a second parts run the same day. Kit-format listings like the 131-163 and 131-131 solve that problem up front. A third mistake is skipping the coolant bleed after the swap, which leaves air pockets that trap temperature near the sensor and give a false reading on the gauge.
When Paying More Pays Off
A higher-priced thermostat earns its keep in two situations. First, when the part includes a matched housing, since replacing the housing and the thermostat together saves a future repair on a known weak point. Second, when a performance-rated thermostat is matched to other cooling upgrades. A high-flow unit on a stock engine doesn’t deliver much, but on a tuned build with an upgraded radiator, it can stabilize coolant temperature under load. The premium is in the matching, not the brand.
