Engine Coolant Thermostat Guide for 2016-2022 Lincoln Navigator
Understand the symptoms of failure and choose the right replacement thermostat for your Navigator's 3.5L engine.
- A P0128 check engine code almost always means you need a new thermostat.
- If your engine overheats, stop driving immediately to prevent severe damage.
- The high replacement cost is due to the OEM part being a complete housing assembly; aftermarket inserts are much cheaper but require the same amount of labor.
- For a reliable, long-term repair, replacing the entire thermostat and housing assembly is the best practice.
Is your Lincoln Navigator's Thermostat Failing?
A faulty thermostat can cause serious engine problems. It typically fails in one of two ways: stuck open or stuck closed. A thermostat that is stuck open will prevent your engine from reaching its proper operating temperature, leading to a check engine light and poor performance. A thermostat that is stuck closed is more dangerous, as it will cause the engine to overheat, which can lead to severe and expensive engine damage.
Stuck Closed: Do Not Drive
If your temperature gauge is in the red or you have a warning light for engine temperature, pull over and shut off the engine immediately. Driving an overheating engine for even a few minutes can cause catastrophic damage.
Common Symptoms of a Bad Thermostat
- Check Engine Light: A common sign of a thermostat stuck open is the P0128 trouble code, which means the engine isn't warming up as quickly as the computer expects. 🎬 Watch: A mechanic explains what the P0128 code means for you.
- Engine Overheating: The temperature gauge climbs into the red. This is the most serious symptom and indicates the thermostat is likely stuck closed.
- Engine Running Too Cool: The temperature gauge never reaches the normal operating range, especially during highway driving. Your engine may feel sluggish.
- Poor Heater Performance: If the engine doesn't get hot enough, the coolant won't be hot enough to provide warm air to the cabin.
- Fluctuating Temperature Gauge: The needle may move erratically between hot and cold, indicating the thermostat is struggling to regulate temperature. 🎬 See how to test for a bad thermostat in ten minutes.
Choosing the Right Aftermarket Thermostat
For the 2016-2022 Navigator, the original thermostat is part of a larger housing assembly. When shopping for a replacement, you'll find both the complete housing and just the thermostat insert. The very high cost of an OEM replacement is for the entire assembly. Aftermarket options give you more choice.
- Standard Replacement (Gates, Motorad): These brands offer OE-equivalent thermostats. They are designed to meet the original 190°F temperature specification and are a reliable, cost-effective choice for daily driving. Gates is a well-known supplier of OE-type parts.
- Performance (Mishimoto): Mishimoto is known for performance cooling components. They may offer thermostats with slightly lower opening temperatures (e.g., 160°F or 170°F). While this can keep the engine running cooler, it's generally intended for tuned or high-performance vehicles and may not be ideal for a stock Navigator, potentially affecting efficiency and emissions.
Pro Tip: Housing or Just the Thermostat?
The low aftermarket prices you see are often for just the thermostat insert. However, the original housing is plastic and can become brittle over time. The high labor cost is the same whether you replace the whole assembly or just the insert. To avoid future leaks, replacing the entire thermostat housing assembly is often the recommended repair.
Known Issues, Recalls, and TSBs
As of early 2026, there are no specific recalls or widespread Technical Service Bulletins (TSBs) from Lincoln for thermostat failure on the 2016-2022 Navigator. Some owners have reported issues with leaking plastic fittings and clamps on related heater hoses, which can also cause coolant loss. A recall for 2021 models (NHTSA ID: 22V-346) mentioned a risk of underhood fire, but a specific cause was not linked directly to the thermostat.
Frequently Asked Questions
Why is the thermostat replacement cost so high for this vehicle?
The high cost is due to the OEM part being an integrated thermostat and housing assembly, which is expensive. Labor costs are also significant because accessing the thermostat requires removing the air intake and other components.
My mechanic found a P0128 code. What does that mean?
P0128 stands for "Coolant Temperature Below Thermostat Regulating Temperature." It means your engine is not reaching its proper operating temperature within a specified time. The most common cause for this code is a thermostat that is stuck open.
Can I replace the thermostat myself?
While possible for an experienced DIY mechanic, it is a moderately difficult job. It requires draining the cooling system and removing the air intake assembly to access the thermostat housing. For most owners, professional installation is recommended.
🎬 Watch this complete guide to replacing the EcoBoost thermostat and pump.Should I buy the thermostat insert or the whole housing assembly?
Given the plastic construction of the original housing and the labor involved, it is generally recommended to replace the entire housing assembly. This prevents the risk of the old housing cracking or leaking shortly after you've paid for the labor to replace just the thermostat insert.
Helpful Videos
Technical Specifications
OEM Part Numbers: HL3Z8575A HL3Z8575B HL3Z-8575-A HL3Z-8575-B
Standard Opening Temperature: 190°F / 88°C. The part is typically an integrated thermostat and housing assembly.
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.
- Lincoln Navigator:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is your Lincoln Navigator's Thermostat Failing?
- Stuck Closed: Do Not Drive
- Common Symptoms of a Bad Thermostat
- Choosing the Right Aftermarket Thermostat
- Pro Tip: Housing or Just the Thermostat?
- Known Issues, Recalls, and TSBs
- Frequently Asked Questions
- 🎟️ Get 5% Off