A Guide to the Engine Coolant Thermostat for the 2003-2007 Mitsubishi Outlander
Keep your Outlander's engine temperature in check by understanding and choosing the right thermostat.
- A failing thermostat can cause either overheating (stuck closed) or a cold-running engine with no heat (stuck open).
- There are no specific recalls or TSBs for the thermostat on this vehicle, so failure is typically due to age and wear.
- Replacement is a DIY-friendly job, located at the end of the lower radiator hose.
- Quality aftermarket brands like Gates and Stant are reliable alternatives to the more expensive OEM part.
Is Your Outlander's Thermostat Failing?
A thermostat is a simple part, but when it fails, it can cause problems that are hard to ignore. Thermostats can fail in two ways: stuck open or stuck closed. Both situations can cause issues for your Outlander's engine.
Symptoms of a Bad Thermostat
- Engine Overheating: If the thermostat is stuck closed, it won't allow coolant to flow to the radiator. Your temperature gauge will climb into the red, and you might hear boiling or gurgling sounds from the engine. This is a serious condition that can cause major engine damage.
- Engine Takes Too Long to Warm Up: If the thermostat is stuck open, it allows coolant to flow to the radiator all the time. This makes it very difficult for your engine to reach its normal operating temperature, especially in colder weather.
- Poor Heater Performance: Your car's heater uses hot coolant to warm the cabin. If the thermostat is stuck open, the coolant never gets hot enough, and your heater will blow lukewarm air.
- Erratic Temperature Gauge: A failing thermostat can cause the temperature needle on your dashboard to swing back and forth unpredictably.
- Check Engine Light: A thermostat that is stuck open can trigger the Check Engine Light with code P0128, which indicates the engine coolant temperature is below its regulating temperature. 🎬 Watch: How to replace the coolant sensor to fix code P0128.
Known Issues, Recalls, and TSBs
Based on extensive searches of NHTSA records and technical service bulletins, there are no specific recalls or TSBs issued for the engine coolant thermostat on the 2003-2007 Mitsubishi Outlander. While recalls exist for this generation for issues like crossmember corrosion, the thermostat itself has not been the subject of a specific factory campaign.
Choosing the Right Aftermarket Thermostat
While an OEM thermostat from Mitsubishi is a reliable choice, quality aftermarket parts are also available and can save you money. Aftermarket brands often fall into different quality tiers.
Tier 1: OEM Equivalents & Premium Aftermarket
These brands are often trusted by professional mechanics and are known for their quality control. For your Outlander, this tier includes brands that aim for OEM form and function.
- Gates & Stant: These are well-regarded brands in the cooling system world. They are generally considered a safe and reliable choice, often close to OEM quality.
- Beck Arnley: This brand is known for sourcing parts from various manufacturers, sometimes even re-boxing the original OEM part. Quality is generally good, but can be inconsistent depending on their supplier for a specific part.
Tier 2: Standard Aftermarket
These brands offer a balance of affordability and performance. They are a good option for daily drivers and budget-conscious repairs.
- Motorad: Motorad is one of the largest thermostat manufacturers in the world and even produces them for other brands. While some users report long life, others have experienced premature failures, especially with their 'fail-safe' models. Sticking to their standard thermostat is often recommended.
- Calorstat by Vernet & Facet: These are established European brands that are widely available and offer a dependable, standard replacement option.
Specialty Brands
- Mishimoto: Known for performance cooling products, Mishimoto offers thermostats that are often designed for high-performance applications. While generally high quality, it may be overkill for a stock Outlander.
Pro Tip: When replacing your thermostat, it's a good idea to also replace the thermostat gasket or seal. Many thermostats come in a kit that includes a new gasket. Also, consider replacing the coolant temperature sensor at the same time, as it is located nearby and you will have already drained the coolant.
Cost Comparison
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Thermostat | $16.90 - $68.95 |
| New OEM Thermostat | $40 - $65 |
| Shop Labor Cost | $73 - $107 |
| Total Professional Replacement | $130 - $400+ (Varies by parts used) |
Frequently Asked Questions
Where is the thermostat located on a 2003-2007 Mitsubishi Outlander?
The thermostat is located inside a housing at the end of the lower radiator hose, where it connects to the engine block. You will need to remove the air filter box and intake tube to get clear access to it.
Is replacing the thermostat a difficult job?
For a moderately experienced DIYer, this is a manageable job. It requires draining some coolant, removing the air intake for access, and unbolting a two-bolt housing. The difficulty is low, and it can typically be done in about an hour.
🎬 See this step-by-step walkthrough for installing a new thermostat.Should I use a 'fail-safe' thermostat?
Fail-safe thermostats are designed to lock in the open position if they fail. While this prevents a catastrophic overheating event, it can also leave you stranded with no heat and poor engine performance. Many mechanics prefer to use a standard, non-fail-safe thermostat from a quality brand.
Do I need to replace the whole thermostat housing?
Not usually. For the 2003-2007 Outlander, the thermostat is a separate part that fits inside the housing. Unless the housing itself is cracked, leaking, or heavily corroded, you typically only need to replace the thermostat and its gasket.
Helpful Videos
Technical Specifications
OEM Part Numbers: MD315301 MD328070 MQ701063
Standard Temperature: 180°F (82°C). The thermostat is a standalone part that fits within a separate housing.
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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.
- Mitsubishi Outlander:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your Outlander's Thermostat Failing?
- Symptoms of a Bad Thermostat
- Known Issues, Recalls, and TSBs
- Choosing the Right Aftermarket Thermostat
- Tier 1: OEM Equivalents & Premium Aftermarket
- Tier 2: Standard Aftermarket
- Specialty Brands
- Cost Comparison
- Frequently Asked Questions
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