Engine Coolant Thermostat Guide for the 1971-1976 Dodge Colt
Keep your classic Colt's Mitsubishi engine running at the right temperature by understanding, diagnosing, and replacing a faulty thermostat.
- A failing thermostat can cause your Colt to either overheat (stuck closed) or run too cool (stuck open).
- Since OEM parts are unavailable, choose a quality aftermarket brand like Gates or Beck Arnley with the factory temperature rating.
- This is an inexpensive and simple repair that is very suitable for a DIY mechanic with basic tools.
- Always replace the gasket with the thermostat to ensure a leak-free seal.
Is Your Dodge Colt's Thermostat Failing?
A thermostat is a simple part, but when it fails, it can cause noticeable problems. Because the 1971-1976 Dodge Colt is a rebadged Mitsubishi, its cooling system is straightforward, making diagnosis relatively easy. A thermostat typically fails in one of two ways: stuck open or stuck closed.
Stuck Closed: The Overheating Risk
If the thermostat fails to open, coolant cannot get to the radiator to be cooled. This will cause the engine to overheat quickly, especially in traffic. Continuing to drive an overheating car can lead to severe engine damage, like a blown head gasket. If your temperature gauge suddenly climbs into the red, pull over as soon as it is safe to do so.
Stuck Open: The Overcooling Problem
If the thermostat is stuck open, coolant will flow to the radiator constantly. This prevents the engine from reaching its proper operating temperature. Symptoms include your heater not blowing hot air, a temperature gauge that stays in the 'cold' range, and potentially worse fuel economy over time.
Choosing the Right Aftermarket Thermostat
For a vehicle from the early 1970s, original "Mopar" or Mitsubishi thermostats are no longer in production. Your only practical option is a new aftermarket part. Fortunately, several reputable brands are available.
It's common in the auto parts industry for one company to manufacture thermostats for many different brands, a practice known as whitelabeling. Motorad is a major manufacturer that produces thermostats sold under various other brand names, including some from Gates and Beck Arnley at times.
- Good Tier (Standard Replacement): Brands like Gates, Beck Arnley, and Motorad are common, affordable choices that meet standard specifications. Gates is well-regarded for cooling system components, and Beck Arnley specializes in parts for import vehicles like your Mitsubishi-made Colt. Given the simplicity of this engine, a standard thermostat from any of these brands is usually sufficient.
- Performance Tier: Brands like Mishimoto or Edelbrock offer performance-oriented thermostats. These might open at a lower temperature, which is intended for modified, high-performance engines. For a stock Dodge Colt, using a performance thermostat is unnecessary and could even be detrimental, preventing the engine from reaching its optimal temperature. Stick with a standard replacement thermostat with the factory-specified temperature rating.
Pro Tip: Always replace the thermostat gasket or O-ring at the same time as the thermostat itself to prevent coolant leaks. These are often included with the new thermostat or sold separately for a low cost.
Typical Cost for a New Thermostat
Replacing the thermostat on a 1971-1976 Dodge Colt is an inexpensive repair. The parts are affordable, and the labor is straightforward.
| Part or Service | Estimated Cost |
|---|---|
| New Aftermarket Thermostat | $9.85 - $40.43 |
| Shop Labor | $90 - $150 |
Frequently Asked Questions
Can I replace the thermostat myself?
Yes, this is a very DIY-friendly job for a beginner. The process involves partially draining the coolant, removing the upper radiator hose from the thermostat housing, unbolting the housing, swapping the old thermostat and gasket for the new ones, and then reassembling and refilling the coolant. The thermostat is typically located at the top of the engine where the upper radiator hose connects.
What temperature thermostat should I buy for my Dodge Colt?
You should always use a thermostat with the same temperature rating as the original. For most cars from this era, this is typically a 180°F or 195°F thermostat. Using a thermostat with a lower temperature rating can cause the engine to run too cool, leading to increased fuel consumption and engine wear.
Are there any recalls for the Dodge Colt thermostat?
No, there are no active recalls or technical service bulletins (TSBs) from the NHTSA related to the engine coolant thermostat for the 1971-1976 Dodge Colt.
Should I run my car without a thermostat?
No, you should not run your engine without a thermostat. Doing so will cause the engine to warm up very slowly and likely never reach its proper operating temperature, which increases fuel consumption and engine wear. In some situations, it can even cause overheating in traffic because the coolant flows too quickly through the radiator to cool down effectively.
Technical Specifications
OEM Part Numbers: MD972905
The 1971-1976 Dodge Colt was equipped with a Mitsubishi 4G32 1.6L engine. The correct thermostat is a standard-flow type, typically rated to open at 180°F.
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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.