Mercury Comet Engine Coolant Thermostat Guide (1960-1968)
Keep your classic Comet's engine at the right temperature by choosing the best new thermostat.
- A failing thermostat can cause serious engine damage if stuck closed, or poor performance if stuck open.
- For a stock Comet, a standard 195°F thermostat from Gates or Motorad is a reliable and affordable choice.
- For modified V8s or for added cooling performance, consider a high-flow thermostat from Edelbrock, Mr. Gasket, or Mishimoto.
- Replacement is an easy DIY job for most owners and should take less than an hour with basic tools.
Signs of a Failing Thermostat in Your Comet
A thermostat is a simple part, but when it fails, it can cause noticeable problems. It usually fails in one of two ways: stuck open or stuck closed.
🎬 Watch: 7 common symptoms of a failing thermostatStuck Closed: High-Risk Failure
This is the more serious failure. If the thermostat sticks shut, it prevents coolant from reaching the radiator. Your engine will overheat quickly. Signs include a temperature gauge needle spiking into the red, steam from under the hood, and potential coolant leaks from pressure buildup. If you see these signs, shut off the engine immediately to prevent serious damage like a warped cylinder head or blown head gasket.
Stuck Open: Low-Risk Failure
If the thermostat sticks open, coolant flows to the radiator constantly. This makes it very difficult for your engine to reach its proper operating temperature. Symptoms include your temperature gauge never reaching the normal range, your car's heater blowing lukewarm or cool air, and decreased fuel economy because the engine runs rich.
Choosing the Right Aftermarket Thermostat
For a classic car like the 1960-1968 Mercury Comet, finding a "new old stock" (NOS) or original equipment (OEM) thermostat is nearly impossible and often unnecessary. Today's aftermarket parts often meet or exceed the quality of the originals from the 1960s. The choice comes down to standard replacement versus performance.
Brand Tiers for Your Mercury Comet
- Standard Replacement (Good): Brands like Gates and Motorad are widely available and offer reliable, budget-friendly options that meet original specifications. They are a solid choice for daily drivers and stock restorations. Note that many brands, including Gates, sometimes re-box thermostats made by Motorad.
- Heavy-Duty / Performance (Better): Brands like Mr. Gasket and Edelbrock offer high-flow thermostats. These are often built with more robust materials and are designed to allow more coolant to pass through when open. They are a great upgrade for Comets with modified engines (like an added Edelbrock intake manifold) or for owners who want extra peace of mind, especially in warmer climates.
- Modern Performance (Best): Mishimoto specializes in high-performance cooling systems. Their thermostats are engineered for precision and often open at a slightly lower temperature to begin the cooling process sooner. This makes them ideal for high-performance V8s or cars that see demanding use.
What Temperature Rating Should You Choose?
For most stock Comet engines (like the 144, 170, 200, and 289), a 180°F or 195°F thermostat is appropriate. A 195°F thermostat is generally better for engine efficiency and cleaner combustion. A lower temperature thermostat (e.g., 160°F or 180°F) is often used in performance applications to keep the engine cooler, but for a stock daily driver, it can reduce heater performance in the winter. Always check your service manual, but a 195°F thermostat is a safe, standard choice.
Aftermarket Thermostat Cost for 1960-1968 Mercury Comet
| Part Tier | Price Range |
|---|---|
| Standard (Gates, Motorad) | $7.93 - $15.00 |
| Performance (Mr. Gasket, Edelbrock) | $22.00 - $30.00 |
| Premium Performance (Mishimoto) | $30.00 - $68.95 |
Frequently Asked Questions
Is replacing the thermostat a DIY job?
Yes, for most owners with basic tools. On classic engines like the inline-six and small-block V8s found in Comets, the thermostat housing is typically on top of the engine at the front, held on by two bolts. You'll lose a small amount of coolant, so have a catch pan ready. 🎬 See this step-by-step thermostat replacement on a 1961 Comet Always replace the gasket when you replace the thermostat.
Do I need a special thermostat for my Comet's V8 engine?
While a standard thermostat will work, V8 engines, especially modified ones, benefit from a high-flow thermostat from a brand like Edelbrock or Mr. Gasket. This ensures the larger engine gets adequate coolant flow under load.
Are there any recalls for the cooling system on my Comet?
No, there are no specific recalls for the engine coolant thermostat or cooling system on 1960-1968 Mercury Comets according to NHTSA records. Any issues are related to age and wear.
Should I also replace the thermostat housing?
Inspect the housing when you replace the thermostat. These old cast iron or steel parts can become corroded, pitted, or cracked over 50+ years. If the surface where the gasket seals is rough or damaged, it's best to replace the housing 🎬 Watch: How to fix a leaking thermostat housing to prevent leaks.
Helpful Videos
Technical Specifications
OEM Part Numbers: C1DZ-8592A C3DZ-8592B
Standard temperature ratings are 180°F and 195°F. Housing is typically cast iron or steel, secured by two bolts. Gasket 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.
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Signs of a Failing Thermostat in Your Comet
- Stuck Closed: High-Risk Failure
- Stuck Open: Low-Risk Failure
- Choosing the Right Aftermarket Thermostat
- Brand Tiers for Your Mercury Comet
- What Temperature Rating Should You Choose?
- Aftermarket Thermostat Cost for 1960-1968 Mercury Comet
- Frequently Asked Questions
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