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If your Mitsubishi Eclipse is running unusually hot or not reaching normal operating temperature, replacing the thermostat can restore stable engine temps and cabin comfort. Choosing the right Mitsubishi Eclipse thermostat matters because fitment, opening temperature, and build quality directly affect how quickly your engine warms and how consistently it stays within safe limits.This guide covers seven shortlisted thermostats chosen for fitment accuracy and temperature regulation. We evaluated each option against key criteria such as opening temperature tolerance and sealing reliability to help you find a suitable replacement. Read on for what to look for before installing a new unit.
Looking for other parts? See all Mitsubishi Eclipse parts & accessories.
Top Picks at a Glance
| Best overall The best all-around choice for most situations | AISIN THM-011 Engine Coolant Thermostat with Gasket |  |
| Best Quality Built to a higher standard if you want something more solid | Mishimoto Racing Thermostat for Mitsubishi Eclipse (1995–1999) |  |
| Best Value The sweet spot between price and what you get | A-Premium Engine Coolant Thermostat with Seal |  |
| Best Budget The cheapest option that still gets the job done reliably | INFINAUTO Engine Coolant Thermostat MD972905 for Mitsubishi Eclipse (1990–1999) |  |
| Highest Rated A top-rated pick with lots of positive feedback | AISIN THM-006 Engine Coolant Thermostat with Gasket |  |
| Most popular A crowd favorite that many people choose with confidence | MotoRad 7420-195 Fail-Safe Thermostat (195°F) |  |
| Best Seller A high-volume bestseller chosen again and again | ROVIKE Engine Thermostat (replacement for Toyota 90916-A3003) |  |
1. AISIN THM-011 Engine Coolant Thermostat with Gasket
| Manufacturer Part Number | THM-011 |
|---|---|
| OEM Part Number | MD174233 |
| Included Components | Thermostat and O-ring |
| Voltage | 12 Volts |
The AISIN THM-011 is a direct-fit replacement thermostat designed to restore proper coolant flow and temperature control in compatible vehicles. Installed in place of a failed unit, it controls coolant circulation to maintain the engine at its specified operating temperature, helping prevent overheating and reduce cold running. Notable features include OEM-matched form, fit, and function plus an included gasket for a complete swap. The thermostat is manufactured to the supplier's original specifications and marketed as using high-quality materials for long life and consistent operation. In practice this means straightforward installation for a mechanically competent DIYer or tech and reliable temperature regulation after replacement. Limitations are few but relevant: fitment depends on engine application so you must confirm it is the correct thermostat for your Eclipse variant and year, and the listing does not include vehicle-specific installation hardware beyond the gasket. If you need a performance thermostat with altered opening temperature or a custom cooling solution, this stock-match unit is not designed for that role.
Best for: Balanced buyers who prioritize a reliable, factory-matching replacement to maintain normal cooling performance in their Mitsubishi Eclipse rather than pursuing performance modifications.
Less Ideal for: Drivers seeking a higher-temperature or performance thermostat for track use or custom cooling setups should consider performance-focused alternatives instead.
- Factory-quality design for correct form, fit, and function
- Includes gasket for a complete replacement install
- Consistent, OE-specified opening temperature for reliable engine temperature control
- Made by a reputable automotive parts supplier with robust manufacturing standards
- Requires verifying exact engine fitment before purchase
- Not intended for performance tuning or altered temperature characteristics
Verdict: Aisin THM-011 is a dependable, factory-matching thermostat for Eclipse owners who want a direct, long-lasting replacement rather than a performance upgrade.
2. Mishimoto Racing Thermostat for Mitsubishi Eclipse (1995–1999)
| Fits | Mitsubishi Eclipse 1995-1999 |
|---|---|
| Activation Temperature | 155°F (68°C) |
| Material | Metal |
| Manufacturer Part Number | MMTS-ECL-95TL |
This Mishimoto racing thermostat is a direct-fit replacement for 1995–1999 Mitsubishi Eclipse models that opens at a lower temperature than the factory unit to push coolant through the system sooner. It is typically used on modified or turbocharged engines where reducing peak temperatures helps reliability and sustained performance. Notable features include a 155°F activation point that is lower than the OEM spec and a metal construction with a polished finish for durability. In practice the thermostat helps the cooling system stabilize at a cooler operating point, reducing knock risk and thermal strain under high-load driving. Installation is straightforward because it is designed for a stock fit, and the product is backed by Mishimoto's lifetime warranty. Limitations include the nature of lower-temperature operation, which can increase warm-up time and slightly affect heater output in cold climates, and it is intended specifically for the listed Eclipse years rather than universal fitments.
Best for: Performance-oriented owners seeking a reliable cooling upgrade for modified or turbocharged 1995–1999 Mitsubishi Eclipse vehicles who prioritize lower operating temperatures to protect the engine under high load.
Less Ideal for: Drivers who prioritize quickest warm-up times, maximum heater performance in cold climates, or who own vehicles outside the 1995–1999 Mitsubishi Eclipse range should consider other options.
- Activates at 155°F for earlier coolant flow and lower peak engine temperatures
- Designed as a direct-fit replacement for easy installation on 1995–1999 Mitsubishi Eclipse
- Durable metal construction with polished finish for long-term use
- Backed by Mishimoto lifetime warranty
- Lower activation temperature can lengthen engine warm-up time and reduce cabin heater output in cold weather
- Fitment limited to 1995–1999 Mitsubishi Eclipse models
Verdict: A purpose-built, lower-activation thermostat that helps keep tuned Mitsubishi Eclipse engines cooler under load.
3. A-Premium Engine Coolant Thermostat with Seal
| Start to Open Temperature (℃) | 89℃ |
|---|---|
| Gasket or Seal Included | Yes |
| Material | Metal and Rubber |
| Package Quantity | 1 |
This A-Premium thermostat is a direct replacement-style unit intended to regulate engine temperature by opening at about 89°C and sealing coolant flow when closed. It is sold as a single thermostat with a gasket included and is constructed from metal and rubber components. Installation is typical of thermostats: drain some coolant, swap the housing, replace the gasket, and refill the system. For a practical optimizer it delivers solid functional value—simple fitment for compatible Mitsubishi models and an included seal reduce parts shopping and repeat trips. The metal construction should withstand normal under-hood conditions, while the specified start-to-open temperature suits standard cooling strategies. Limitations to note are modest documentation and the generic aftermarket nature, which may differ slightly from factory parts in finish or long-term durability. If you need a precision-calibrated or OEM-branded unit for high-performance tuning, this unit may not be ideal.
Best for: Buyers who prioritize practical, cost-conscious maintenance and want a straightforward replacement that restores normal cooling operation without premium branding concerns.
Less Ideal for: Owners seeking an OEM-branded thermostat for exact factory match or those doing performance tuning who need nonstandard opening temperatures should consider other options.
- Includes gasket to simplify installation and avoid extra parts purchases
- Starts to open at 89°C, matching common factory cooling setpoints
- Metal and rubber construction appropriate for routine engine temperatures
- Sold as a single, ready-to-install thermostat compatible with specified Mitsubishi models
- Aftermarket unit may show slight fit or finish differences from factory parts
- Limited vehicle-specific installation guidance included in packaging
Verdict: A budget-friendly, ready-to-install replacement thermostat that hits standard opening temperature and includes a seal, making it a practical choice for routine Mitsubishi Eclipse cooling system repairs.
4. INFINAUTO Engine Coolant Thermostat MD972905 for Mitsubishi Eclipse (1990–1999)
| Manufacturer | INFINAUTO |
|---|---|
| Position | Inner |
| Material | Metal |
| OE Number | MD972905 |
| Vehicle fitment | Mitsubishi Eclipse 1990-1999 4G63 |
This INFINAUTO thermostat is a direct-fit replacement designed to regulate coolant flow for Mitsubishi Eclipse 1st and 2nd generation 4G63 engines. Made of metal and sold as a single unit, it opens and closes with coolant temperature to route water to the radiator and keep the engine in its optimal range. The listing emphasizes improved durability and corrosion resistance versus basic designs and claims factory-quality testing. Installation is straightforward for anyone familiar with basic engine work and the compact, inner-positioned unit fits the OEM location. Expect practical benefits like restoring correct warm-up behavior, preventing overheating from a stuck-closed thermostat, and improved long-term corrosion resistance compared with stamped-plastic types. Limitations are that this is an aftermarket non-factory part so exact matching of thermostat calibration or finish may vary and there is limited documentation on valve temperature rating or included gasket hardware, so you should confirm compatibility and have replacement sealing parts ready if needed.
Best for: Budget-conscious Mitsubishi Eclipse owners who want a low-cost, straightforward replacement part to restore cooling system function without paying for a dealer thermostat.
Less Ideal for: Those seeking an exact factory-spec replacement with documented valve temperature or rebuildable OEM components should consider a branded factory-quality thermostat instead.
- Made of metal for better wear and corrosion resistance than basic plastic thermostats
- Designed to fit the inner thermostat position for direct replacement on listed Mitsubishi engines
- Simple single-piece unit that is quick to install for DIY mechanically inclined owners
- No explicit listed thermostat opening temperature or calibration details
- Sold as an aftermarket part so exact fit or finish may differ from factory units
Verdict: A no-frills metal replacement thermostat that offers affordable, serviceable cooling control for Mitsubishi Eclipse 4G63 engines.
5. AISIN THM-006 Engine Coolant Thermostat with Gasket
| Manufacturer Part Number | THM-006 |
|---|---|
| OEM Part Number | MD328070 |
| Position | Front, Rear |
| Brand | AISIN |
This AISIN THM-006 thermostat is a direct-fit replacement designed to restore proper engine cooling by opening at the correct factory-specified temperature. It is typically installed when a failing thermostat causes overheating or poor cabin heat; the kit includes the thermostat and an O-ring/gasket for a single straightforward swap. AISIN emphasizes OEM-matched form, fit, and function and the machined exterior suggests consistent construction and durability. For a reliability-focused repair on a Mitsubishi Eclipse this part reduces the risk of recurring cooling issues by matching the correct operating temperature and using proven manufacturing standards. Limitations are few but real: fitment depends on specific model years and engine variants so you must confirm compatibility before purchase, and the kit only contains the thermostat and gasket so any adjacent components that are worn will require separate replacement. Installation still requires basic mechanical skill or a shop if you are not comfortable working on the cooling system.
Best for: Reliability-focused owners who prioritize a factory-quality, long-lasting repair for their Mitsubishi Eclipse and prefer parts that match original temperature specifications.
Less Ideal for: Buyers seeking a comprehensive cooling system overhaul or those unaware of their exact model/engine fitment should consider a full inspection or alternative kits that include additional components.
- Factory-quality design matched to specified operating temperature
- Includes gasket/O-ring for a complete thermostat swap
- Machined exterior and OEM part number traceability indicate consistent manufacturing
- Compatibility varies by year and engine so fitment must be verified
- Contains only thermostat and gasket, other cooling parts sold separately
Verdict: A dependable, factory-matching replacement thermostat with gasket that’s ideal for reliability-focused Mitsubishi Eclipse repairs when fitment is confirmed.
6. MotoRad 7420-195 Fail-Safe Thermostat (195°F)
| Brand | MotoRad |
|---|---|
| Model Name | 7420-195 |
| Temperature Rating | 195 Degrees |
| Material | Metals, High-temperature Resistant Plastics |
The MotoRad 7420-195 is a fail-safe replacement thermostat built to reduce the risk of engine damage if a cooling-system component fails. Installed in the thermostat housing, it operates like a normal 195°F thermostat but contains a precision piston that forces the valve to stay open if overheating occurs, allowing full coolant circulation until the vehicle can be shut down. Typical use is direct replacement during routine cooling-system service or as an upgrade for owners worried about overheating. The unit is made from metal and high-temp plastics, tested and calibrated by the manufacturer, and users report generally reliable fit and performance where it matches vehicle applications. Limitations to consider are mixed field reports of isolated failures and a seal sensitivity that can make installation care important. Also this part is sold as a single thermostat without additional gaskets or hardware, so you may need to supply installation seals or a professional install for best results.
Best for: Convenience-driven buyers who want a replacement that reduces the chance of catastrophic overheating and prefer a straightforward swap during routine cooling-system maintenance.
Less Ideal for: Drivers who prioritize lowest upfront cost without concern for fail-safe protection or those planning a DIY install without sourcing proper seals and installation hardware.
- Fail-safe design that locks open under overheating to preserve coolant flow and reduce risk of engine damage
- Factory-quality testing and calibration for consistent temperature control
- Fits as a direct replacement for supported vehicle applications
- Some user reports of early failures or seal issues after installation
- Sold as a single unit without installation gasket or extra hardware
Verdict: Choose this thermostat if you want a factory-quality fail-safe unit that can keep coolant flowing during an overheating event, but be prepared to supply installation seals or professional fitment.
7. ROVIKE Engine Thermostat (replacement for Toyota 90916-A3003)
| Brand | ROVIKE |
|---|---|
| Included Components | Engine Thermostat |
| Connectivity Technology | Wi-Fi |
| Power Source | Battery Powered |
| Material | Metal, Plastic |
This ROVIKE engine thermostat is a basic, aftermarket replacement designed to control coolant flow and maintain engine operating temperature. It is sold as a direct replacement for part numbers like 90916-A3003 and arrives as a single thermostat intended for straightforward swap-in installation. Buyers report it functioning as expected when it fits, and the metal/plastic construction is what you would expect from an economy aftermarket part. The listing includes an extensive compatibility list covering many Toyota and Lexus model years, but fitment accuracy varies so verifying the exact part number and physical dimensions before installation is important. There are positive user reports of reliable temperature control and value, while a few reviews note incorrect fitment on specific vehicles. Expect a no-frills unit that restores proper thermostat operation when it matches the factory part, but be prepared to confirm fit or return if your application differs from the listing.
Best for: A risk-averse mainstream buyer replacing a failed thermostat who prioritizes restoring reliable cooling-system function without paying dealer prices and will verify the exact part number before ordering.
Less Ideal for: Owners needing guaranteed factory-quality fitment, exact OEM tolerances, or integrated hardware should consider purchasing a factory replacement from an authorized parts source instead.
- Listed as a direct replacement for common Toyota part numbers such as 90916-A3003
- Simple single-piece thermostat design that is easy to install for routine cooling-system repairs
- Many buyers report it restores normal engine temperature control at a lower cost than dealer parts
- Compatibility is broad on the listing but some customers report incorrect fitment for certain model years
- Aftermarket construction may not match factory-quality tolerances in every unit
- No gasket, sensor, or additional hardware included in the package
Verdict: A budget-friendly aftermarket thermostat that can restore cooling control when the part number matches, but buyers must double-check fitment for their vehicle.
Choosing the Right Mitsubishi Eclipse Thermostat: Key Factors to Consider
Fitment and Mounting Compatibility
Exact fitment is critical because the thermostat must mate precisely with the Eclipse's housing and coolant passages to function properly. A thermostat that does not seat correctly can cause bypass, poor flow control, or leaks that lead to temperature fluctuations.
When evaluating fitment, confirm flange shape, bolt pattern, and overall dimensions match the vehicle's thermostat housing. Proper alignment also ensures sensor interfaces sit correctly so the engine control and temperature gauges get accurate readings.
Thermostat Opening Temperature
The opening temperature determines when coolant begins to flow through the radiator and affects warm-up speed and idle temperature. Choosing a thermostat with the correct nominal opening temperature helps the engine reach optimal operating range without running too cool or overheating.
Consider the factory-specified opening temperature for the Mitsubishi Eclipse engine and choose replacements with a close tolerance range. Small deviations can change engine efficiency, emissions, and cabin heater performance.
Sealing and Gasket Quality
A reliable seal between the thermostat and housing prevents coolant leaks and pressure loss, which can trigger overheating or air intrusion. The gasket material and the precision of mating surfaces influence long-term sealing performance.
Look for thermostats offered with high-quality gaskets or integrated rubber seals. Also assess whether the housing interface is prone to warping or requires a specific sealant technique during installation to avoid future leaks.
Actuation and Material Durability
Thermostat actuation mechanism quality affects how predictably the valve opens and closes across many heat cycles. Materials exposed to coolant should resist corrosion and degradation to maintain consistent operation over time.
Components such as the valve, spring, and pintle should be made from corrosion-resistant metals and durable polymers. Durable construction reduces the risk of sticking, slow response, or collapse under repeated thermal cycling.
Installation Accessibility and Serviceability
Ease of installation matters because some thermostats are located in confined spaces that complicate replacement. A design that allows straightforward removal and reinstallation reduces labor time and the chance of installation errors.
Consider whether the thermostat includes replacement hardware and a gasket, and whether auxiliary tasks like draining coolant or removing ancillary components are necessary. Clear fitment documentation and straightforward mounting can make a DIY replacement more viable.
Compatibility With Cooling System Sensors
Some vehicles rely on nearby sensors or housings that must remain correctly positioned after thermostat replacement. Ensuring the replacement unit does not interfere with sensor placement helps maintain accurate engine temperature readings.
Verify that the thermostat housing design allows sensor access and that any sensor ports are unobstructed. Compatibility with the vehicle's pressure and temperature sensor interfaces prevents diagnostic errors and maintains proper engine management behavior.
How We Chose the Best Mitsubishi Eclipse Thermostat
To assemble this list we applied focused, vehicle-specific filters and real-world performance dimensions relevant to Mitsubishi Eclipse owners. Primary criteria included exact fitment to the Eclipse cooling passages and mounting points, thermostat opening temperature and tolerance, and the quality of the housing and gasket surfaces to minimize seal leaks. We also considered valve actuation reliability under typical operating cycles, corrosion resistance of materials in coolant environments, and compatibility with the vehicle's cooling system sensors and housings.We excluded units lacking clear fitment documentation, thermostats with nonstandard opening temperatures for the engine, and parts with poor material specifications that increase risk of premature failure. Our selections prioritize components that balance dependable temperature control, durable sealing, and straightforward installation for the Mitsubishi Eclipse.
Our full evaluation process is outlined in our review methodology.
FAQ
What are common thermostat symptoms overheating in a Mitsubishi Eclipse?
Common signs of overheating include a rising engine temperature gauge, coolant loss, steam from the engine bay, and heater output that becomes erratic. You may also notice the cooling fan running constantly or heat-related warning lights. These symptoms often indicate restricted coolant flow or a thermostat that is not opening properly.
How to test a thermostat on a Mitsubishi Eclipse?
A basic test involves monitoring engine temperature behavior and feeling radiator hose temperatures as the engine warms. With care, you can remove the thermostat and place it in a pot of gradually heated water to observe the opening temperature. Always follow safety precautions and consult a service manual for the correct nominal opening temperature and testing procedure for the specific engine.
What does an engine running cold thermostat stuck open feel like?
If the thermostat is stuck open, the engine may take a long time to reach operating temperature or may run below normal. You might experience poor heater performance and reduced fuel efficiency. The temperature gauge will often remain lower than normal even after extended driving.
Can a thermostat housing seal leak cause overheating?
Yes, a leaking seal at the thermostat housing can allow coolant to escape and introduce air into the cooling system. Loss of coolant or trapped air pockets reduce cooling efficiency and can lead to overheating. Ensuring a proper seal and checking the gasket and mating surfaces helps prevent these issues.
How do I find the correct thermostat part number fitment for my Mitsubishi Eclipse?
Refer to the vehicle's service manual, OEM parts diagrams, or the vehicle identification information to match the thermostat part number to your engine variant. Look for documentation that lists flange dimensions, opening temperature, and mounting details to confirm proper fitment. If in doubt, consult a qualified technician for verification.
Conclusion
When choosing a new thermostat for a Mitsubishi Eclipse, prioritize exact fitment, the correct opening temperature, and reliable sealing to avoid leaks and temperature instability. Balance material durability and actuator quality with ease of installation to reduce the likelihood of premature failure.Remember that small tradeoffs exist between faster warm-up and long-term stability. Focus on components that match the vehicle's specifications and offer proven sealing and consistent actuation to maintain safe engine temperatures and dependable heater performance.
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