Chevrolet Impala Engine Coolant Thermostat Guide (2014-2020)
Is your 2014-2020 Impala's temperature gauge acting strange or is the heater blowing cold? Your thermostat might be the problem.
- A thermostat stuck open is the most common failure, causing a P0128 code, slow warm-up, and poor heat.
- For best results, choose an ACDelco (OEM) replacement; they are designed for your Impala's specific temperature needs.
- It is highly recommended to replace the entire thermostat and housing assembly, not just the thermostat itself.
- If you have a 2.5L engine, inspect the coolant temperature sensor wiring for signs of coolant leaks when doing the job.
Is Your Impala's Thermostat Failing?
A thermostat is a wear-and-tear item. When it fails, it usually gets stuck in either the open or closed position, causing distinct problems. Knowing the signs can save you from a much bigger headache, like engine damage from overheating.
Choosing the Right Aftermarket Thermostat
When replacing the thermostat on your 2014-2020 Impala, you'll find several options. Many thermostats for this vehicle are sold as a complete unit with the plastic or metal housing. Given that the housing itself can crack and leak, replacing the entire assembly is often the smartest repair. 🎬 Watch this walkthrough for locating and replacing the 2.5L thermostat. Here’s a breakdown of brand quality:
- Tier 1: OEM or Equivalent (ACDelco): ACDelco is the original equipment manufacturer for General Motors. Choosing an ACDelco thermostat ensures you get the same part your Impala was built with, designed for the exact fit and correct temperature regulation. For a critical part like this, sticking with the OEM brand is the safest choice to avoid performance issues.
- Tier 2: Reputable Aftermarket (Gates, Calorstat): Gates is a well-known and generally trusted aftermarket brand. While reliable, some forum users have noted that their thermostats can sometimes run slightly cooler than the OEM part. Calorstat is another established aftermarket supplier. These brands offer a good balance of price and quality.
- Tier 3: Value Brands (Motorad, Facet): Motorad is a massive manufacturer that produces thermostats for many different brands, including store brands like Duralast. Quality can be inconsistent; some users report premature failures, while others have no problems. These are often the most affordable and readily available options, but may carry a higher risk of not performing exactly like the original.
Known Issue: Leaking Coolant Temperature Sensor (2.5L Engine)
A Technical Service Bulletin (TSB) exists for some Impalas with the 2.5L engine. The engine coolant temperature (ECT) sensor can develop an internal leak. Coolant can then travel up the wiring harness and reach the main computer (ECM), causing a short and strange electrical problems, like a false 'Hood Ajar' warning on the dash. If you are replacing your thermostat, it is a good time to inspect the ECT sensor connector for any signs of green coolant residue.
| Part Type | Price Range |
|---|---|
| New OEM (ACDelco Assembly) | $75 - $150 |
| New Aftermarket (Assembly) | $22 - $125 |
| Shop Labor Cost | $150 - $250 |
Frequently Asked Questions (FAQ)
Do I need to replace the whole thermostat housing?
For the 2014-2020 Impala, it is highly recommended. The thermostat is often integrated into the housing, and these housings (especially plastic ones) can become brittle and crack over time, causing leaks. Replacing the complete assembly ensures all related components are new and reduces the chance of a future leak from the housing itself.
What is the P0128 code?
The P0128 trouble code means "Coolant Temperature is Below Thermostat Regulating Temperature." This is the most common code you'll see for a failing thermostat. It means the engine's computer sees that the engine isn't warming up as quickly as it should, which is almost always caused by a thermostat that is stuck open.
🎬 See how a mechanic diagnoses a P0128 fault code.Should I use a special tool to replace the thermostat?
While most of the job can be done with standard sockets and ratchets, a pair of hose clamp pliers is extremely helpful for removing the spring-type clamps on the radiator hoses. A torque wrench is also recommended to tighten the housing bolts to the correct specification and prevent cracking the new housing.
Do I need to drain all the coolant to change the thermostat?
Yes, you need to drain the cooling system before starting. When you remove the thermostat housing, any coolant above that level will spill out. Draining the radiator into a clean pan allows you to reuse the coolant if it's in good condition, though replacing it with fresh, 50/50 premixed DEX-COOL coolant is often a good idea.
🎬 Watch: Step-by-step guide to changing your coolant and thermostat.Are there any recalls for the thermostat on my Impala?
No, there are no specific recalls from the NHTSA for the engine coolant thermostat on the 2014-2020 Chevrolet Impala.
Helpful Videos
Technical Specifications
OEM Part Numbers: 12689037 15-81939 15-81764
Standard operating temperature is typically 180°F. Most replacements are sold as a complete housing assembly with the thermostat and gasket included.
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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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