Dodge Mirada Engine Coolant Thermostat Guide (1980-1983)
Keep your Mirada's Slant 6 or V8 engine running at the right temperature by choosing the correct new thermostat.
- A thermostat typically fails either stuck open (slow warm-up, no heat) or stuck closed (overheating).
- For a stock Dodge Mirada V8, a 195-degree thermostat is the standard replacement.
- Aftermarket is the only realistic option; brands like Gates are standard, while Edelbrock offers a performance upgrade.
- Always replace the thermostat gasket and inspect hoses when performing this simple, DIY-friendly job.
Symptoms of a Failing Thermostat in a Dodge Mirada
A thermostat is a simple part, but it can cause major issues when it fails. It typically fails in one of two ways: stuck open or stuck closed.
Thermostat Stuck Closed
This is the more serious failure. When the thermostat is stuck closed, hot coolant can't get to the radiator to cool down. This quickly leads to engine overheating, which can cause severe and expensive damage like warped cylinder heads. Symptoms include:
- Temperature gauge rising to the red zone and staying there.
- Steam coming from under the hood.
- Coolant boiling over and leaking from the reservoir or radiator cap.
- The upper radiator hose will be very hot, while the lower hose may feel much cooler.
Thermostat Stuck Open
This failure is less dangerous but still needs to be fixed. A thermostat stuck open allows coolant to flow to the radiator constantly. This makes it very difficult for your engine to reach its proper operating temperature. Symptoms include:
- Engine takes a very long time to warm up.
- Temperature gauge stays on the low end of the scale, or even drops during highway driving.
- Heater does not blow hot air, or only blows lukewarm air.
- Check Engine Light may come on with a code like P0128 (Coolant Temperature Below Thermostat Regulating Temperature).
Choosing the Right Aftermarket Thermostat
For a classic car like the Dodge Mirada, new OEM Mopar thermostats are generally not available. Aftermarket parts are the go-to option and offer good quality for this simple component. The key is to choose a reputable brand and the correct temperature rating. For most stock 318 V8 engines, a 195-degree thermostat is the standard choice.
Brand Quality Tiers
Not all aftermarket brands are the same. They generally fall into a few categories:
- Standard Replacement (Gates, Motorad): These brands are designed to meet original factory specifications. They are a reliable choice for daily drivers and stock vehicles. It's worth noting that many brands, including Gates, are sometimes manufactured by Motorad. While widely used, some owners have reported mixed reliability with Motorad parts, including failures out of the box.
- Performance (Edelbrock, Mr Gasket): Brands like Edelbrock offer high-performance thermostats often made with more durable materials like stainless steel and brass. These are a good option if you have a modified engine or want extra peace of mind, though they come at a higher cost. Some user reviews suggest Edelbrock may be more reliable than other performance options like Mr Gasket.
Estimated Costs for Thermostat Replacement
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Thermostat | $7 - $56 |
| Thermostat Gasket | $2 - $10 |
| Shop Labor | $75 - $150 |
Frequently Asked Questions
What temperature thermostat should I use for my Dodge Mirada?
For a stock V8 engine, a 195-degree thermostat is generally the correct factory specification. Using a lower temperature thermostat (e.g., 180-degree) was a common practice in the past but can affect engine efficiency and emissions on computer-controlled cars. For the 1980-1983 Mirada, sticking with the factory-spec temperature is recommended for stock applications.
Is it difficult to replace the thermostat on a Mirada?
No, this is generally considered an easy DIY job for someone with basic tools. The thermostat is usually located at the front of the engine where the upper radiator hose connects to the engine block. The process involves draining some coolant, unbolting the housing, swapping the thermostat and gasket, and refilling the coolant. The entire job typically takes less than an hour.
Should I replace anything else at the same time?
Yes. Always use a new thermostat housing gasket. It's also a great time to inspect your radiator hoses for cracks, swelling, or softness and replace them if they are old. Checking the condition of your radiator cap is also a good idea, as a faulty cap can cause overheating issues.
What are "fail-safe" thermostats?
Some aftermarket thermostats are designed to lock in the open position if the engine overheats. This prevents a catastrophic stuck-closed failure, allowing coolant to flow and protecting the engine from severe damage. However, once it locks open, it must be replaced.
Technical Specifications
Standard Temperature: 195°F for V8 engines. Check specific engine for exact requirements.
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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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