Note: This article contains affiliate links. If you click on these links and make a purchase, I may earn a small commission at no extra cost to you. This helps support my research and content. Read my full affiliate disclaimer here.
If you drive a Ram 3500, a properly functioning thermostat matters for engine longevity, cabin comfort, and towing reliability. Picking the right Ram 3500 thermostat helps maintain correct operating temperature under heavy loads and varied climates, reducing the risk of overheating or inefficient warm-up. This guide presents our shortlisted top picks for the Ram 3500 thermostat and explains the key factors we used to evaluate each option, including fitment specifics and thermal response. Read on for practical guidance before you choose a replacement.
Top Picks at a Glance
| Best Reviewed A top-rated pick with lots of positive feedback | RARAYC Aluminum Engine Coolant Thermostat Housing Assembly |  |
| Most Popular A crowd favorite that many people choose with confidence | WMPHE Aluminum Thermostat Housing Assembly for Ram 2500/3500/4500/5500 (6.4L) |  |
| Best Quality Built to a higher standard if you want something more solid | Sixity Auto Gates Engine Coolant Thermostat for Ram 2500 6.7L L6 (2013–2019) |  |
| Best Budget The cheapest option that still gets the job done reliably | QAGGUM Aluminum Engine Thermostat Housing, Replacement for Ram ProMaster 1500/2500/3500 |  |
| Most Sold A high-volume bestseller chosen again and again | MotoRad 7416-203 203°F Fail-Safe Thermostat |  |
| Best Value for Money The sweet spot between price and what you get | MITZONE Aluminum Thermostat Housing Assembly with Thermostat and Gasket |  |
| Best Overall The best all-around choice for most situations | Gates 33915 Engine Coolant Thermostat |  |
1. RARAYC Aluminum Engine Coolant Thermostat Housing Assembly
| Material | 1060-H32 aluminum |
|---|---|
| Compatible vehicles | 2011–2021 Chrysler/RAM lineup including Ram 1500/2500/3500 and related models |
| Manufacturer part number | 902-3036 |
| Replaces part numbers | 5184570AH, 68136754AA, 5184570AJ, 902-3036 |
This RARAYC thermostat housing replaces the factory plastic outlet with a machined aluminum unit intended for direct swap-in on compatible Ram applications. It is used where the stock housing and thermostat are removed and the new assembly bolts into the engine, providing the coolant passage and thermostat location. The housing is made from 1060-H32 aluminum for improved tensile strength and corrosion resistance compared with plastic, which can reduce the chance of cracking or warping over time. Multiple customer reports note straightforward installation and good fit for Ram models, and several include cross-reference part numbers for compatibility. Some users found manufacturing flaws such as a poorly seated check valve or thin gasket, so careful inspection and a quality gasket are advisable before install. Expect a simple replacement that can extend service life over plastic housings, but be prepared to swap the gasket or address minor casting imperfections if they appear.
Best for: Reliability-focused owners who want a more durable metal replacement for the factory housing to reduce repeat failures and long-term coolant leaks.
Less Ideal for: Buyers who prefer a guaranteed drop-in solution without any potential for minor fit or finish issues should consider a different factory-quality branded replacement.
- Aluminum construction offers greater strength and corrosion resistance than factory plastic housings
- Machined exterior finish for a cleaner fit and appearance
- Direct-replacement design built to match factory mounting points and thermostat location
- Multiple part-number cross-references increase the chance of correct fit for Ram 3500 applications
- Some units show quality-control issues such as a misaligned check valve or poor gasket fit requiring replacement
- Not supplied with a high-quality gasket in all cases so buyers may need to purchase one separately
Verdict A sturdier aluminum replacement housing aimed at reliability-focused owners, though inspect for minor quality issues and plan to use a good gasket.
2. WMPHE Aluminum Thermostat Housing Assembly for Ram 2500/3500/4500/5500 (6.4L)
| Brand | WMPHE |
|---|---|
| Model | 902-304 |
| Compatible Engines | 6.4L |
| Manufacturer Part Number | 902-3045 4893177AB |
This aluminum thermostat housing assembly replaces the factory housing on compatible Ram 6.4L trucks and controls coolant flow to keep the engine at its designed operating temperature. Installation is straightforward for anyone comfortable with basic engine work: remove the old housing, transfer any sensors or fittings, fit the new housing and torque the bolts to spec. The housing is cast from aluminum rather than plastic, which improves heat dissipation and resistance to cracking or deformation over time. That can reduce the chance of coolant leaks and may extend service life compared with plastic units. Reported failures exist, including thermostats sticking open, so expect occasional defective units and check the thermostat operation after installation. This is a practical, lower-cost option if you want a more durable replacement than stock plastic parts, but you may still need to source a replacement thermostat or return the unit if you encounter a faulty valve.
Best for: Convenience-driven buyers who want a straightforward, more durable factory-replacement housing for their Ram 3500 to avoid frequent plastic-housing failures and simplify DIY repairs.
Less Ideal for: Buyers seeking a guaranteed long-term solution without any risk of early thermostat failure or those unwilling to perform basic hands-on installation should consider professional remanufactured options or dealer parts.
- Aluminum construction offers better heat dissipation and higher resistance to cracking than plastic housings.
- Built as a direct replacement for Ram 6.4L thermostat housing to simplify installation.
- Improves durability in high-temperature and corrosive coolant environments compared with common plastic alternatives.
- Some users report thermostat valve failures, including sticking open after limited use.
- May require transfer of sensors or fittings from the old housing which adds minor installation steps.
Verdict A budget-friendly, aluminum direct-replacement housing that’s more durable than plastic but watch for occasional thermostat failures.
3. Sixity Auto Gates Engine Coolant Thermostat for Ram 2500 6.7L L6 (2013–2019)
| Brand | Sixity Auto |
|---|---|
| Manufacturer | Sixity Auto |
| Manufacturer Part Number | 4036024480 |
| Compatible Vehicles | Ram 2500 6.7L L6 2013-2019 |
This thermostat is a direct replacement designed to control coolant flow and maintain operating temperature in the 6.7L Cummins Ram 2500 from 2013 through 2019. It installs in place of the factory unit and is used whenever a failed thermostat causes overheating, poor warm-up, or cooling system faults. The listing highlights Gates-brand compatibility and includes the sealing hardware needed for a straightforward swap. In practice the unit should restore proper thermostat operation and temperature regulation, helping the engine reach and hold its intended temperature under load. Limitations to note are fitment scope and that the listing targets the Ram 2500 6.7L L6; if your vehicle is a Ram 3500 this part may not be confirmed for fitment and you should verify compatibility before purchase. Expect a simple mechanical replacement with no electronic controls and the usual need to bleed and refill the cooling system after installation.
Best for: Performance-oriented buyers who prioritize reliable, factory-style temperature control and want a straightforward replacement part to return a diesel engine to correct operating temperature.
Less Ideal for: Shoppers seeking thermostat options specifically validated for Ram 3500 models or those who want advanced thermostats with variable or electronically controlled temperature management.
- Direct-replacement design intended to match factory thermostat function
- Includes seal and hardware for one-step installation
- Compatible with 6.7L L6 Ram 2500 model years 2013–2019, simplifying fit confirmation
- Branded Gates part compatibility suggests factory-quality design and combustion-cooling reliability
- Fitment is specified for Ram 2500 6.7L models and not listed for Ram 3500 in the product details
- No electronic or adaptive temperature control features compared with some modern thermostats
Verdict A factory-style replacement thermostat for 6.7L Ram 2500s that restores standard temperature control but is not confirmed for Ram 3500 fitment.
4. QAGGUM Aluminum Engine Thermostat Housing, Replacement for Ram ProMaster 1500/2500/3500
| Fitment note | Ram ProMaster 1500/2500/3500 (years per manufacturer listing) |
|---|---|
| Material | Aluminum |
| Manufacturer part reference | Replace 902-3036 |
This aluminum thermostat housing replaces the factory unit on compatible Ram ProMaster 1500/2500/3500 model years listed by the manufacturer and provides the mounting and sealing surface for the engine thermostat. It is typically used when the original housing is cracked, leaking, or corroded and is installed by removing the old housing, swapping the gasket or O-ring, and fastening the new part with the factory bolts. Notable features include a cast aluminum construction that resists deformation under heat and a supplied rubber O-ring to reduce the chance of coolant leaks. For a budget-focused buyer this housing offers a straightforward, direct-replacement path and can be fitted during a DIY repair to restore coolant routing without complex modifications. Limitations are that long-term durability may vary compared with factory-quality parts and fit or finish can differ between aftermarket batches, so careful inspection at install and the possibility of earlier replacement should be considered.
Best for: Budget-conscious owners seeking an affordable, DIY-friendly replacement for a failed thermostat housing on their Ram ProMaster who prioritize low cost and quick repair over long-term OEM parity.
Less Ideal for: Owners who prioritize factory-equivalent longevity or long service intervals should consider a factory-quality replacement or dealer parts instead.
- Cast aluminum construction resists high-temperature deformation compared with cheaper plastics
- Includes rubber O-ring to help achieve a tighter coolant seal at the thermostat junction
- Designed as a direct replacement for listed Ram ProMaster models for straightforward installation
- Lightweight design simplifies handling during DIY installation
- Aftermarket build quality can be inconsistent which may affect long-term durability
Verdict A low-cost aluminum replacement that makes a quick DIY fix for a leaking or damaged thermostat housing on Ram ProMaster vans, with some risk to long-term durability.
5. MotoRad 7416-203 203°F Fail-Safe Thermostat
| Included Components | (1) Fail-Safe Thermostat, 203 °F |
|---|---|
| Voltage | 230 Volts |
| Power Source | Battery Powered |
| Temperature Control Type | thermostatic |
The MotoRad 7416-203 is a drop-in fail-safe thermostat designed to replace the factory unit in compatible Dodge, Chrysler, Jeep and Ram engines, including Ram 3500 models listed in the fitment. It is built with a locking feature intended to prevent coolant loss and catastrophic overheating by failing closed or holding a controlled position, and MotoRad states the part is tested and calibrated before shipping. Installation is the same as a factory replacement, so most home mechanics or professionals will fit it without modification. The thermostat is offered as a vehicle-specific fit and is advertised as manufactured to meet or exceed factory standards, which makes it a convenient option when you want a direct replacement. Buyer reports are mixed: many users report proper fit and reliable operation in Ram trucks while a minority report units that failed to open during testing. If you choose this part, bench-test it before installation and consider professional installation for peace of mind when avoiding engine risk.
Best for: Risk-averse mainstream buyers who want a direct, factory-style replacement for their Ram 3500 and prioritize a tested, drop-in part that minimizes installation complexity.
Less Ideal for: Buyers seeking adjustable or performance-tuned thermostats or those unwilling to bench-test parts before installation should consider other options.
- Vehicle-specific fit for affected Ram models makes installation straightforward
- Fail-safe, lockable design aimed at preventing coolant loss and engine damage
- Factory-quality manufacturing claims and pre-shipment calibration/testing
- Simple analog/button control and battery power means no vehicle reprogramming
- Some user reports of units failing to open during bench tests indicate inconsistent quality control
- Listed 203°F opening is fixed so it may not match every service preference
Verdict A practical, vehicle-specific fail-safe replacement for Ram 3500 owners who want a factory-style thermostat but test units before installation due to occasional quality reports.
6. MITZONE Aluminum Thermostat Housing Assembly with Thermostat and Gasket
| Manufacturer | MITZONE |
|---|---|
| Model | 001-503ALU |
| Exterior | Aluminium |
| OEM Part Number | 5184570AG, 5184570AH, 5184570AI, 5184570AJ, 902-3036 |
This MITZONE assembly replaces the factory plastic thermostat housing with a cast-aluminum unit and includes the thermostat, gasket, and mounting screw for a mostly plug-and-play swap. It regulates coolant flow and opens at 95 C, so it performs the same basic function as the original while offering improved durability from the metal housing. Typical use is a direct replacement during routine cooling-system repairs or when the stock plastic housing has failed; installation is straightforward and reviewers report accurate fitment and no leaks when installed correctly. The aluminum body resists heat and pressure better than plastic, reducing the chance of cracking or warping over time, but the integrated design means the thermostat and housing are a matched set so you cannot replace just the valve alone. Some users reported occasional thermostat or gasket issues, so double-check the gasket seating at installation and be prepared to recheck after the first thermal cycles. For a budget-focused upgrade that targets longer life than the original plastic part, this is a practical option for Ram 3500 owners with the specified engine.
Best for: Practical optimizer buyers who prioritize a durable, budget-friendly upgrade to the factory plastic housing and want a ready-to-install replacement that reduces the likelihood of future housing failures.
Less Ideal for: Drivers seeking a serviceable setup where the thermostat can be swapped independently or those who prefer OEM-branded parts and dealer-supplied replacements.
- Cast aluminum housing is more heat- and impact-resistant than the original plastic design
- Includes thermostat, gasket, and mounting screw for a complete replacement
- Reported to fit and align with factory mounting points for straightforward installation
- Opening temperature specified at 95 C, matching expected engine thermal control
- Thermostat is bonded into the housing so you must replace the entire assembly if the valve fails
- A few users reported early thermostat or gasket issues requiring reinstallation or replacement
Verdict A cost-effective, longer-lasting aluminum replacement for the factory plastic thermostat housing that is ideal for Ram 3500 owners wanting a practical durability upgrade.
7. Gates 33915 Engine Coolant Thermostat
| Manufacturer Part Number | 33915 |
|---|---|
| Manufacturer | GATES |
| OEM Part Number | 5011456AA, 5086739AB, 5292712, 68005464AA, 68005464AB |
| Included Components | Engine Coolant Thermostat |
The Gates 33915 is a straightforward engine coolant thermostat built to replace the factory unit on Ram 3500 Cummins engines. It uses a positive piston thermostatic element and sturdy metal construction to open and close at its calibrated temperature, helping the engine reach and hold normal operating temperature. Typical use is as a direct replacement during routine cooling-system service or when the truck is running too cool or exhibiting wide temp swings. Buyers will notice consistent temperature control reported by users, simple installation and a factory-calibrated mechanism that resists pressure-related variations. Limitations are that the part does not include visible temperature markings on the housing and long-term durability can vary by operating conditions, so results depend on proper installation and compatible housing/gasket condition. This is a practical, no-frills replacement for Ram 3500 owners who want predictable cooling behavior without modifying the stock cooling strategy.
Best for: Balanced, practical Ram 3500 owners who want a reliable factory-quality replacement to restore stable operating temperatures without performance modification.
Less Ideal for: Owners seeking performance or modified cooling behavior, or those who need a complete housing gasket kit delivered with the thermostat.
- Factory-calibrated thermostatic element for consistent open/close temperature
- Positive piston design reduces sensitivity to pressure changes
- Sturdy metal construction for a robust feel
- Direct-fit replacement for Dodge Ram 3500 Cummins applications
- No temperature marking on the thermostat body to confirm set point
- Does not include housing or gasket, which may be needed for complete replacement
Verdict A dependable, factory-calibrated replacement thermostat that restores stable coolant temperatures for Ram 3500 Cummins trucks without tuning or extra parts.
Choosing the Right Ram 3500 Thermostat: Key Factors to Consider
Correct Fitment and Mounting
Exact fitment to the Ram 3500 thermostat housing ensures the part seats properly and aligns with coolant passages. Mismatched dimensions or an incorrect flange can create sealing gaps, leading to leaks or erratic coolant flow. Proper mounting also affects thermostat orientation and bypass flow paths. Choosing a unit that matches the original mounting pattern reduces installation time and lowers the risk of introducing stress on the housing or hoses.
Opening Temperature and Thermal Response
The thermostat s specified opening temperature determines when coolant begins circulating through the radiator, so it directly influences engine warm-up time and operating temperature. A thermostat that opens too early can cause the engine to run cool, which affects efficiency and emissions, while one that opens too late increases overheating risk. Thermal response, or how consistently the valve opens and closes at its rated temperature, matters for stable temperature control during towing or idling. Look for thermostats with clearly stated temperature ratings and consistent actuation characteristics.
Seal Integrity and Gasket Compatibility
A reliable seal at the housing prevents coolant loss and maintains system pressure. The condition and compatibility of the thermostat housing seal or gasket influence long-term leak resistance, especially after repeated heat cycles or when using different coolant formulations. Choose thermostats that include or are compatible with high-quality gaskets, and ensure replacement seals match the housing design to avoid weeping or overtightening damage during installation.
Material Quality and Corrosion Resistance
Thermostat components are exposed to coolant and heat, so materials that resist corrosion and thermal fatigue extend service life. Brass, stainless steel, and coated steels are common in critical parts like the valve and spring, while housings may be metal or high-grade polymer. Better material quality reduces the chance of sticking, valve distortion, or structural failure when the engine is under heavy load or in harsh environmental conditions.
Bypass Flow Characteristics
Internal bypass ports help regulate coolant circulation before the thermostat fully opens, affecting warm-up behavior and head gasket protection. The size and design of the bypass path determine how much coolant recirculates through the engine versus being routed to the radiator at lower temperatures. Consider how bypass flow interacts with engine warm-up and heater core performance, especially if you tow or operate in cold climates where maintaining cabin heat quickly is important.
Ease of Installation and Serviceability
A thermostat that is straightforward to install reduces labor time and the chance of installation errors. Features that help include clear sealing surfaces, included gaskets, and design elements that aid alignment with the housing. Serviceability matters if you anticipate future inspections or repeated replacements. Thermostats that avoid overly tight torque requirements and that use standard fasteners make maintenance simpler for both DIYers and technicians.
FAQ
What are common signs of a failing thermostat in a Ram 3500?
Common signs include the engine overheating under load, the engine taking too long to reach normal operating temperature, or wide temperature gauge fluctuations. You might also notice poor cabin heat output or coolant leaks near the thermostat housing. These symptoms often point to a thermostat that is sticking closed, stuck open, or has a failed seal.
How do I test a thermostat without removing it?
You can observe coolant temperature behavior and heater performance while the engine warms up and idles. Rapid overheating, no warm-up, or a temperature gauge that stays unusually low often indicates thermostat issues. For a definitive test, many technicians monitor inlet and outlet hose temperatures or use a scan tool to read coolant temperature sensors while the engine reaches operating conditions.
Can a thermostat cause my engine to run cold or overheat?
Yes. A thermostat stuck open will allow continuous coolant flow and often causes the engine to run cooler than intended, while one stuck closed will prevent flow to the radiator and typically leads to overheating. Both conditions can affect performance and component longevity, so addressing thermostat faults promptly is important.
Should I replace the gasket or seal when changing the thermostat?
Replacing the thermostat housing gasket or seal during installation is usually recommended. Reusing an old seal can increase the risk of leaks, especially if the original material has compressed or been damaged during removal. New gaskets ensure a proper mating surface and help maintain system pressure.
How long does a thermostat typically last on a heavy-duty truck?
Thermostat lifespan varies with usage, coolant quality, and driving conditions. On heavy-duty trucks that tow or operate under high loads, thermostats often face greater thermal stress and may show issues sooner than passenger cars. Regular inspection during routine service helps catch early signs of sticking or leaks before they cause major problems.
How We Chose the Best Ram 3500 Thermostat
We focused on thermostats that specifically list compatibility with the Ram 3500 and meet factory-style fitment standards. Our selection criteria emphasized accurate fitment and mounting dimensions, consistent opening and closing temperatures, and reliable valve operation under load and varied ambient conditions. We also considered build quality of the housing and sealing surfaces, corrosion resistance of internal components, and availability of compatible gaskets or seals. We excluded universal or generic thermostats that require significant modification, units lacking clear temperature specifications, and parts without documented mechanical durability. Our approach prioritized parts that minimize installation hassle, restore correct thermal management, and reduce the chance of coolant leaks or premature failure.
Our full evaluation process is outlined in our review methodology.
Conclusion
When choosing a Ram 3500 thermostat, prioritize correct fitment, the proper opening temperature, and durable sealing to maintain reliable engine temperatures under load. Consider material quality and bypass design to match your typical driving and towing needs. Balancing thermal response with installation ease will reduce downtime and the chance of coolant leaks. Use the factors above to select a unit that restores stable temperature control and fits your service preferences.
