Ford CF6000 Engine Coolant Thermostat Guide (1986-1990)
Keep your 6.6L or 7.8L diesel engine from overheating by understanding common thermostat problems and choosing the right replacement part.
- A failing thermostat can cause your engine to either overheat (stuck closed) or run too cool (stuck open).
- For a critical part on a work truck, many mechanics prefer OEM (Motorcraft) thermostats for reliability, but quality aftermarket brands like Gates are a good alternative.
- Always replace the thermostat gasket at the same time to prevent leaks.
- When replacing, check for a small air bleed passage near the thermostat housing and ensure it is not clogged with old coolant debris.
Symptoms of a Failing Thermostat
A thermostat can fail in two ways: stuck open or stuck closed. Each has its own set of symptoms.
🎬 Watch this breakdown of common bad thermostat symptoms.Stuck Closed: High Risk of Overheating
This is the most dangerous type of failure. When the thermostat is stuck closed, coolant can't get to the radiator to cool down. This will cause the engine to overheat very quickly, which can lead to severe and expensive damage like warped cylinder heads.
- Temperature gauge quickly climbs into the red.
- Engine feels unusually hot or you see steam from under the hood.
- You may hear gurgling or boiling sounds from the engine area.
Stuck Open: Poor Performance
If the thermostat is stuck open, the engine may never reach its proper operating temperature because coolant is always circulating through the radiator. This leads to other problems over time.
- Engine takes a very long time to warm up.
- Temperature gauge stays in the low range, or drops when driving downhill.
- Heater blows lukewarm or cold air.
- Noticeable decrease in fuel economy.
Choosing the Right Aftermarket Thermostat
For a work truck like the CF6000, reliability is key. While an OEM Ford/Motorcraft part is a benchmark for quality, reputable aftermarket brands offer a good balance of performance and price.
| Brand Tier | Brands | Notes |
|---|---|---|
| OEM / Premium | Motorcraft (Ford) | Considered the highest quality and best fit for reliability, though often at a higher price. Many mechanics recommend sticking with OEM for this critical part. The original part number is E6HZ-8575-B. |
| Quality Aftermarket | Gates, Calorstat | Gates is a well-respected brand in cooling systems. Calorstat is also known to be an OEM supplier for some vehicle manufacturers and is generally considered a reliable choice. |
| Standard / Economy | Motorad | Motorad is widely available and sometimes used as a private-label brand for auto parts stores. While some of their products work well, they have mixed reviews, with some users reporting premature failures. They are often the most budget-friendly option. |
Mechanic's Tip: Check the Air Bleed
On some older Ford diesel engines, there is a small air bleed ball or valve near the thermostat housing. If you've had dirty coolant, this passage can get clogged with debris. A clogged air bleed can trap air behind the new thermostat, preventing hot coolant from reaching it and causing it to open late or not at all. Make sure this passage is clear when you replace the part.
Frequently Asked Questions (FAQ)
Is replacing a thermostat a DIY job?
For someone with mechanical experience, yes. The job involves draining some coolant, unbolting the thermostat housing (usually where the upper radiator hose connects to the engine), swapping the part and gasket, and then refilling and bleeding the air from the system. The main challenges can be reaching the bolts and cleaning the old gasket material off the metal surfaces without causing damage.
🎬 See how to test and replace a thermostat yourself.What temperature thermostat should I use?
You should always use the temperature rating specified for your engine, which is typically 180°F or 195°F for the Ford 6.6L and 7.8L diesels. Using a thermostat with a different temperature rating can negatively affect engine performance and fuel efficiency. Aftermarket brands will clearly label the part with the OEM temperature.
Should I replace the gasket and housing too?
Always replace the thermostat gasket to prevent leaks. Most new thermostats come with a new gasket. The housing itself usually does not need to be replaced unless it is cracked, corroded, or damaged during removal.
Are there any recalls for the thermostat on my CF6000?
There are no specific recalls or technical service bulletins (TSBs) from the NHTSA related to the engine coolant thermostat for the 1986-1990 Ford CF6000.
Helpful Videos
Technical Specifications
OEM Part Numbers: E6HZ-8575-B
Fits Ford 6.6L & 7.8L inline-6 diesel engines. Common temperature ratings are 180°F and 195°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.
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