A Comprehensive Guide to the Engine Coolant Thermostat for the 2012-2016 Volvo S80
Address common cooling system problems like running too cool, overheating, or a P0128 check engine light code in your S80.
- A P0128 check engine light code almost always indicates a thermostat that is stuck open.
- Always replace the entire thermostat housing assembly, not just the internal thermostat, to prevent leaks.
- For a long-term repair, consider upgrading to an aftermarket aluminum housing to prevent future cracking.
- Replacement requires removing the intake manifold, making it a moderately difficult job for a DIYer.
Is Your Volvo S80 Thermostat Failing?
A failing thermostat on the P3-chassis S80 can cause several noticeable issues. Because the part is a complete housing assembly, failures can be either mechanical (the thermostat itself) or physical (the housing). Here are the most common signs of a problem:
- Engine Running Too Cool (Stuck Open): This is the most common failure. The thermostat gets stuck in the open position, causing coolant to circulate constantly. Symptoms include the engine taking a very long time to warm up, poor heater performance in the cabin, and a drop in the temperature gauge when coasting downhill.
- Check Engine Light (P0128 Code): A thermostat that's stuck open will almost always trigger a check engine light with the code P0128, which means the engine coolant temperature is below its regulating temperature. 🎬 Watch: How to diagnose a P0128 code and faulty thermostat
- Engine Overheating (Stuck Closed): While less common, the thermostat can fail in the closed position. This is a serious issue that prevents coolant from reaching the radiator, causing the engine to overheat quickly. You will see the temperature gauge climb into the red.
- Coolant Leaks: The original thermostat housing is made of plastic, which can become brittle and crack after years of heat cycles. This can cause coolant to leak, often leaving a blue, crusty residue on the engine block below the housing.
- Erratic Temperature Readings: A malfunctioning temperature sensor or a faulty thermostat can send erratic signals, causing the temperature gauge on your dashboard to fluctuate unpredictably.
Always Replace the Full Assembly
The thermostat, housing, and sensor are sold as a single integrated unit for a reason. The plastic housing is a known failure point. Do not attempt to just replace the thermostat insert itself. This often leads to leaks and a repeat repair. Always buy the complete assembly to ensure a proper seal and reliable performance.
Choosing the Right Aftermarket Thermostat
When shopping for a new thermostat assembly, you have several options that vary in quality and price. For this specific part, brand choice matters.
Tier 1 (Upgrade): Aftermarket Aluminum Housing
For owners looking for a permanent solution, aftermarket aluminum thermostat housings are available. These directly replace the failure-prone OEM plastic housing, eliminating the risk of future cracks and leaks. While they may have a higher initial cost, they provide long-term peace of mind and are a highly recommended upgrade.
🎬 See this overview of the upgraded aluminum thermostat housingTier 2 (OEM-Quality Aftermarket): Gates, Mahle, Behr
Brands like Gates, Mahle, and Behr are often the original equipment manufacturers for Volvo. Choosing a part from one of these brands gives you the same fit and performance as the Genuine Volvo part without the dealership price tag. Gates is a well-respected brand in the aftermarket for cooling system components and offers a reliable plastic housing replacement.
Tier 3 (Budget): Professional Parts Sweden (PPS) & Store Brands
Budget-friendly options are available from brands like Professional Parts Sweden and various auto parts store brands. While the lower price is appealing, the quality can be inconsistent for critical parts like this. Some owners have reported premature failures and leaks with budget-tier housings. These may be suitable for a temporary fix but carry a higher risk of failure compared to OEM-quality or aluminum options.
Pro Tip: Consider the Upgrade
If you plan on keeping your S80 for the long term, investing in an aluminum thermostat housing is the smartest choice. It addresses the original design's primary weakness—the plastic construction—for a relatively small price increase over a quality plastic replacement.
Cost of Replacing a 2012-2016 Volvo S80 Thermostat
The cost can be broken down into the part itself and the labor required for installation. On the 3.2L and T6 engines, the intake manifold must be removed to access the thermostat, making labor a significant part of the total cost.
| Part/Service | Estimated Cost |
|---|---|
| New Aftermarket Thermostat Assembly | $77 - $225 |
| New Genuine Volvo Thermostat Assembly | $200 - $300 |
| Shop Labor | $300 - $450 |
| Total Estimated Cost (Aftermarket Part + Labor) | $377 - $675 |
Frequently Asked Questions (FAQ)
Is it difficult to replace the thermostat myself?
For an experienced DIY mechanic, this job is manageable but involved. The main challenge is removing the intake manifold to gain access. It requires disconnecting fuel and vacuum lines, electrical connectors, and working in a tight space. It can take a DIYer 3-5 hours. If you are not comfortable with this level of work, it is best to leave it to a professional.
🎬 Watch: Step-by-step thermostat replacement for 3.0t and 3.2l enginesAre there any recalls for the thermostat on my S80?
No. There are no official recalls or technical service bulletins (TSBs) from Volvo or the NHTSA specifically for engine coolant thermostat failure on the 2012-2016 S80. There was a recall for the fan control module on earlier 2008-2009 models which could cause overheating, but it does not apply to the thermostat on these later model years.
Can I drive my S80 with a bad thermostat?
It depends on how it failed. If it's stuck open and the engine is running too cool (P0128 code), you can drive the car, but you should get it repaired soon. Driving for extended periods with a cold engine can lead to poor fuel economy and increased engine wear. If the thermostat is stuck closed and the engine is overheating, you should pull over immediately and have the vehicle towed to prevent catastrophic engine damage.
Why can't I just buy the thermostat and not the whole housing?
The part is designed as a single, sealed unit. The plastic housing is a common point of failure due to cracking and warping from heat. Attempting to separate the housing to install a new thermostat insert often results in a poor seal, leading to coolant leaks and requiring you to do the job all over again. Replacing the entire assembly is the only way to ensure a reliable, leak-free repair.
Helpful Videos
Technical Specifications
OEM Part Numbers: 31355151
Integrated assembly including thermostat, plastic housing, gasket, and temperature sensor. The thermostat is designed to begin opening at approximately 90°C (194°F).
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.
- Volvo S80:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Is Your Volvo S80 Thermostat Failing?
- Always Replace the Full Assembly
- Choosing the Right Aftermarket Thermostat
- Tier 1 (Upgrade): Aftermarket Aluminum Housing
- Tier 2 (OEM-Quality Aftermarket): Gates, Mahle, Behr
- Tier 3 (Budget): Professional Parts Sweden (PPS) & Store Brands
- Pro Tip: Consider the Upgrade
- Cost of Replacing a 2012-2016 Volvo S80 Thermostat
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off