Chrysler 300 Engine Coolant Thermostat Guide (2005-2023)
Keep your Chrysler 300's engine temperature in check by understanding when and why you need to replace your thermostat.
- A P0128 check engine light code almost always means you need a new thermostat.
- For 2011+ Chrysler 300s with the 3.6L V6, replace the entire thermostat and housing assembly, not just the thermostat.
- Using an OEM Mopar part is often recommended for the 3.6L V6 plastic housing to avoid fitment and quality issues.
- Properly bleeding all air from the cooling system after installation is critical to prevent overheating.
Signs of a Failing Thermostat in Your Chrysler 300
A thermostat can fail in two ways: stuck open or stuck closed. Each has distinct symptoms. A thermostat stuck closed is the most dangerous, as it prevents coolant from reaching the radiator, leading to rapid overheating. A thermostat stuck open is more common and will cause the engine to run too cool.
Common Failure Symptoms
- Check Engine Light: The most frequent sign is a check engine light with code P0128 (Coolant Temperature Below Thermostat Regulating Temperature). This code means your engine isn't warming up as fast as the computer expects, usually because the thermostat is stuck open. 🎬 Learn the top three causes for a P0128 code on Pentastar engines.
- Engine Overheating: If the thermostat is stuck closed, the temperature gauge will climb into the red. You may see steam from the engine or get an "Engine Overheated" message. This is a critical issue that requires you to stop driving immediately.
- Temperature Gauge Fluctuates or Reads Low: A gauge that never reaches the normal operating range (usually the halfway mark) or drops toward cold during highway driving points to a thermostat that is stuck open.
- Poor Heater Performance: If your cabin heater blows lukewarm air, especially in winter, it's often because the engine isn't getting hot enough to provide sufficient heat to the heater core.
- Coolant Leaks: For 2011-2023 models with the 3.6L Pentastar V6, the thermostat is part of a plastic housing assembly that can crack and leak coolant over time.
Choosing the Right Aftermarket Thermostat
When replacing the thermostat on your Chrysler 300, you have a choice between OEM (Mopar) and various aftermarket brands. For many parts, aftermarket is a great value. However, for the Chrysler 300, especially the 2011+ models with the 3.6L Pentastar engine, the quality of the thermostat and its housing is critical.
Some owners and mechanics report issues with aftermarket plastic housings having poor fitment or being made of lower-quality plastic that fails prematurely. For this reason, many recommend using an OEM Mopar part for the integrated thermostat housing on the 3.6L V6. For HEMI V8 engines, which often use a more traditional, separate thermostat 🎬 See how to diagnose and replace a thermostat on HEMI engines., brand choice is more flexible.
Aftermarket Brand Tiers
- Standard Replacement (Gates, Motorad): Brands like Gates and Motorad are well-known aftermarket manufacturers that produce reliable, OEM-temperature (203°F) thermostats. They offer a good balance of quality and value for a standard repair. Motorad also offers a "Fail-Safe" design that locks in the open position if it fails, preventing a catastrophic overheating event.
- OEM-Equivalent (Crown Automotive): Crown Automotive specializes in parts for Chrysler vehicles and aims to provide OEM-quality components. This can be a solid choice if you're looking for a quality part that closely matches the original specifications without the dealer price tag.
- Performance (Mishimoto): Mishimoto offers "racing" thermostats that open at a lower temperature (e.g., 180°F instead of 203°F). These are designed for modified or high-performance engines to increase cooling efficiency. Using a lower-temperature thermostat on a stock engine may keep it from reaching its optimal operating temperature, potentially affecting performance and fuel efficiency, and may still trigger a P0128 code.
- Economy Brands: While very affordable, some lower-cost, lesser-known brands may use materials that don't hold up as well, particularly the plastic housings on later models.
A Note on Housings
For 2011-2023 Chrysler 300s with the 3.6L Pentastar V6, the thermostat is integrated into a larger plastic housing assembly. It is highly recommended to replace the entire assembly 🎬 Watch this step-by-step guide to replacing the 3.6L V6 thermostat housing., not just the thermostat itself, as the plastic can become brittle and is a common source of leaks. For older models and V8s, the thermostat is often a separate part that fits inside a metal housing.
Cost of Replacing a Chrysler 300 Thermostat
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Part | $10 - $65 |
| New OEM (Mopar) Part | $40 - $120 |
| Shop Labor | $100 - $250 |
Costs are estimates and can vary based on your vehicle's engine, your location, and the specific parts chosen.
Frequently Asked Questions
Is it hard to replace the thermostat on a Chrysler 300?
The difficulty depends on the engine. For the 3.6L V6, the thermostat housing is relatively easy to access at the top front of the engine, requiring removal of the engine cover and air intake tube. For HEMI V8 engines, it's similarly located at the front of the engine where the upper radiator hose connects. Most DIY mechanics with basic tools can complete the job in 1-2 hours. The most important part of the job is properly bleeding the air out of the cooling system afterward to prevent overheating.
What temperature thermostat should I use for my Chrysler 300?
For a stock vehicle, you should always use a thermostat with the OEM-specified temperature, which is typically 203°F for most V6 and V8 models. Using a lower temperature thermostat can cause the engine to run too cool, leading to reduced fuel efficiency and a persistent P0128 check engine light.
Are there any recalls for the Chrysler 300 thermostat?
As of late 2023, there are no specific recalls for the engine coolant thermostat on the 2005-2023 Chrysler 300. However, Chrysler has issued Technical Service Bulletins (TSBs) related to the cooling system, including TSB #18-031-11 for a P0128 code and TSB #18-032-11 for a P2181 code (Cooling System Performance), which can be related to thermostat issues. A TSB provides dealers with recommended repair procedures for known problems but is not a recall.
What is the most common mistake when replacing the thermostat?
The most common mistake is not properly bleeding the cooling system after the replacement. Trapped air pockets can cause the engine to overheat, even with a new thermostat. On the 3.6L V6, there is a small bleeder screw on the thermostat housing to help remove air. It's crucial to run the engine with the heater on high and slowly add coolant until all air is purged from the system.
Helpful Videos
Technical Specifications
OEM Part Numbers: 5184977AE 52028898AE
Standard opening temperature for most models is 203°F (95°C). The 3.6L Pentastar V6 uses an integrated thermostat and housing assembly. HEMI V8 models (5.7L, 6.1L, 6.4L) typically use a standalone thermostat.
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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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