Ford LNT8000F (1987-1997) Engine Coolant Thermostat Replacement Guide
Keep your heavy-duty Ford running at the right temperature by understanding how to choose the correct new aftermarket thermostat.
- You MUST identify your specific engine (e.g., Ford 7.8L, Cummins C8.3) before buying a thermostat, as the part is engine-specific.
- A failing thermostat can cause overheating, poor fuel economy, or weak cabin heat.
- For reliability, consider premium aftermarket brands like Gates; always replace the gasket with the thermostat.
- The correct temperature rating (e.g., 180°F) is critical for engine performance and must match your engine's original specification.
Is Your LNT8000F Thermostat Failing?
A bad thermostat can cause serious problems, but the signs are usually clear. The most dangerous issue is a thermostat stuck closed, which will cause your engine to overheat quickly. A thermostat stuck open is less dangerous but still causes problems like poor fuel economy and weak cabin heat in the winter. Watch for these common symptoms:
- Engine Overheating: The temperature gauge climbs into the red. This is the most serious symptom. A thermostat stuck closed is a common cause.
- Engine Running Too Cool: The temperature gauge never reaches the normal operating range. This is usually caused by a thermostat stuck open.
- Temperature Fluctuations: The gauge needle jumps around unpredictably, from cool to hot and back. This can signal a thermostat that is sticking or about to fail completely.
- Poor Heater Performance: If your cab heater isn't blowing hot air, it could be because the engine isn't getting hot enough due to a stuck-open thermostat.
- Coolant Leaks: You might see coolant leaking from around the thermostat housing. This can be caused by a bad gasket or a housing that has cracked from repeated temperature changes.
Identify Your Engine First!
The single most important step is to correctly identify the engine in your LNT8000F. These trucks were available with different engines, most commonly the Ford 6.6L and 7.8L (made by Ford-New Holland) or Cummins diesels (like the C8.3). The correct thermostat and its temperature rating are specific to the engine, NOT the truck model. Using the wrong thermostat can lead to poor performance or engine damage.
Choosing the Right Aftermarket Thermostat
For a vehicle of this age, OEM parts can be hard to find. The aftermarket offers several good options. The key is choosing a quality brand with the correct temperature rating for your specific engine.
Know Your Temperature: The required temperature is stamped on the thermostat itself. For example, many Ford 7.8L engines use a 180°F thermostat that starts to open between 174-181°F and is fully open by 205°F. Cummins engines may have different specifications. Always verify the correct temperature for your engine before buying.
Brand Quality Tiers
When shopping for a new aftermarket thermostat, you'll find several brands available. Here’s a general breakdown of what to expect:
- Good - Motorad: Motorad is a common aftermarket brand that often serves as an original equipment manufacturer for some car companies. They offer a direct-fit, affordable replacement that meets basic requirements. For a standard replacement, Motorad is a functional choice.
- Better - Calorstat: Calorstat by Vernet is a well-known OEM supplier in Europe and is recognized for producing quality parts. They are a solid choice that often meets or exceeds the quality of standard aftermarket parts.
- Best - Gates: Gates is a highly respected brand in the automotive and heavy-duty industry, known for quality components like belts, hoses, and thermostats. For a truck that needs to be reliable, choosing a premium brand like Gates provides extra peace of mind.
Pro Tip: Replace More Than Just the Thermostat
Since you have to drain the coolant to replace the thermostat, it's a perfect time to inspect and replace other cooling system parts. Always replace the thermostat gasket or O-ring. It's also wise to install a new upper radiator hose and check the condition of the thermostat housing for cracks or corrosion.
Cost of a New Aftermarket Thermostat
The cost for a new thermostat is low compared to the engine damage it can prevent. Here is a general breakdown of expected costs for the 1987-1997 Ford LNT8000F.
| Part or Service | Estimated Cost |
|---|---|
| New Aftermarket Thermostat | $12.49 - $107.93 |
| Shop Labor | $100 - $250 |
| Total Professional Replacement | $115 - $360 |
(Prices are estimates and may vary based on location, specific engine, and parts availability.)
Frequently Asked Questions (FAQ)
What temperature thermostat do I need for my Ford 7.8L engine?
Many Ford 7.8L diesel engines use a 180°F thermostat. Service manuals often state it begins to open around 174-181°F and is fully open by about 205°F. However, you should always verify the specific requirement for your engine, as variations exist.
Can I replace the thermostat myself?
Yes, for someone with mechanical experience, this is a manageable job. The main steps involve draining the coolant, removing the thermostat housing (usually on top of the engine at the end of the upper radiator hose), swapping the thermostat and gasket, and reinstalling everything before refilling and bleeding the cooling system. The biggest challenge can be stuck or corroded bolts.
Are there any recalls for the thermostat on this truck?
No specific recalls for the engine coolant thermostat were found for the 1987-1997 Ford LNT8000F. Searches of the NHTSA database did not show any recalls related to this specific component for this vehicle.
Should I use a gasket, sealant, or both?
Always use a new gasket. Some mechanics apply a very thin layer of high-temperature RTV sealant to one side of the gasket to hold it in place during assembly, but avoid using too much as it can squeeze into the cooling system and cause blockages. Follow the instructions on the sealant and allow proper curing time.
Technical Specifications
OEM Part Numbers: 87800842 87803664 3928639 3928640 3913028
Temperature rating is engine-specific. Common ratings for engines in this truck are 180°F or 195°F. The Ford 7.8L often uses a 180°F thermostat. Cummins engines may use a 180°F thermostat. Always verify the correct temperature for your specific engine model.
We Have This Part in Stock
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.
- Ford LNT8000F: