Engine Coolant Thermostat Guide for the 1995-1999 Mitsubishi Eclipse
Keep your 2G Eclipse engine running at the perfect temperature with the right replacement thermostat.
- An OEM Mitsubishi thermostat is strongly recommended by owners for reliability and proper function.
- Always replace the gasket with the thermostat to prevent leaks; it's often sold separately.
- A stuck-open thermostat is the most common failure, leading to a P0128 code and a slow-to-warm engine.
- A stuck-closed thermostat will cause rapid overheating and can destroy your engine; shut the car off immediately if this happens.
Is Your Eclipse Thermostat Failing?
A thermostat is a simple part, but a failure can cause major problems. For the 1995-1999 Eclipse, thermostats most often fail by getting stuck open. This is better than getting stuck closed, but still needs to be fixed. Here are the common signs of a bad thermostat:
- Engine Takes Forever to Warm Up: If your temp gauge barely moves or never reaches the middle of the dial, your thermostat is likely stuck open.
- No Hot Air from Vents: With the engine not reaching full temperature, the coolant isn't hot enough to provide good heat inside the car.
- Check Engine Light (P0128 Code): A thermostat that is stuck open will often cause the engine computer to trigger a P0128 trouble code, which means the engine isn't warming up as fast as it should.
- Engine Overheating: If the thermostat gets stuck closed, coolant can't get to the radiator. Your temperature gauge will quickly shoot into the red. This is a critical situation. 🎬 Watch this step-by-step guide on replacing your 2G thermostat. Pull over and shut off the engine immediately to prevent severe damage.
- Gurgling or Rumbling Sounds: Sounds from the engine or radiator could be a sign of boiling coolant, which can happen when a thermostat is stuck closed.
Choosing the Right Aftermarket Thermostat
For many parts, aftermarket is a great choice. For the thermostat on a 2G Eclipse, you need to be careful. Enthusiast communities strongly recommend using a genuine Mitsubishi OEM thermostat for best results. 🎬 See how to properly test and swap your thermostat. Many have reported that aftermarket thermostats can fail early, leak, or have incorrect flow characteristics for the Eclipse engine. If an OEM part isn't an option, choose a top-tier aftermarket brand known for quality.
Aftermarket Brand Tiers for 1995-1999 Eclipse
| Tier | Brands | Notes |
|---|---|---|
| OEM / Premium Aftermarket | Mitsubishi (OEM), Beck Arnley, Gates | OEM is highly recommended by owners for fit and reliability. Beck Arnley and Gates are generally trusted aftermarket brands that aim for OEM quality. |
| Performance | Mishimoto | Mishimoto offers "racing" thermostats that open at a lower temperature (around 143°F). These are for highly modified, track-focused cars and are not recommended for a daily driven vehicle as they can prevent the engine from reaching its proper operating temperature. Some users have reported quality control issues. |
| Standard / Economy | Motorad, Facet, Calorstat | These are budget-friendly options. However, brands like Motorad have received mixed reviews regarding long-term reliability. Some offer a "fail-safe" feature that locks the thermostat open if it fails, which can prevent overheating but requires immediate replacement. |
Pro Tip: Always buy a new thermostat gasket. Most aftermarket thermostats do not include one, and reusing the old gasket will cause leaks. Thoroughly cleaning the old gasket material from both the engine and the thermostat housing is a critical step for a leak-free installation.
Frequently Asked Questions (FAQ)
What temperature thermostat should I use for my Eclipse?
For a stock or lightly modified 1995-1999 Eclipse, use a thermostat with the factory temperature rating, which is typically 180°F (82°C). Using a lower temperature thermostat on a daily driver can hurt fuel economy and may keep the engine computer from entering "closed-loop" mode, which is needed for efficient operation.
Should I replace the thermostat housing at the same time?
It is usually not necessary unless the old housing is cracked, heavily corroded, or the sealing surface is badly pitted and cannot be cleaned. Inspect it carefully when you remove it.
Is there a recall on the thermostat for the 1995-1999 Eclipse?
No, there are no recalls or widespread Technical Service Bulletins (TSBs) from Mitsubishi or the NHTSA specifically for the engine coolant thermostat on this generation of Eclipse.
What is the little jiggle pin on the thermostat for?
That small pin or valve is a bleeder. It allows trapped air to pass through the thermostat. For a proper installation, this pin should always be facing up (in the 12 o'clock position) to help bleed air out of the cooling system as you refill it.
🎬 Learn the best way to bleed air from your cooling system.Helpful Videos
Technical Specifications
OEM Part Numbers: MD972905
Standard Opening Temperature: 180°F (82°C). The thermostat is located in the housing where the upper radiator hose connects to the engine. A separate gasket is required for installation.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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