A Guide to the Engine Coolant Thermostat for the 2006-2011 BMW M5 (E60)
Everything E60 M5 owners need to know about replacing a faulty S85 engine thermostat.
- The thermostat is a known weak point on the S85 engine and typically fails stuck open, causing a '2B59' fault code and preventing the engine from warming up properly.
- Due to the high labor cost involving the removal of the intake plenums, using a top-tier OEM (Mahle/Behr) or OEM-equivalent brand is strongly recommended to ensure reliability.
- There are no specific recalls for the E60 M5 thermostat, so replacement is a standard maintenance repair.
- While replacing the thermostat, it is a best practice to also replace the two small plastic coolant pipes and their O-rings to prevent future leaks.
Symptoms of a Failing Thermostat in the E60 M5
The thermostat in the S85 engine is a known weak point that often fails over time. Unlike some cars where a thermostat fails closed and causes rapid overheating, the E60 M5 thermostat is designed to fail in the open position. This is a fail-safe to protect the engine from severe damage. While safer, a stuck-open thermostat will still cause problems you need to address.
The most common signs include:
- Check Engine Light: A faulty thermostat will almost always trigger a check engine light. The most common fault code stored is 2B59 (Coolant Thermostat Monitor), which indicates the engine isn't reaching its required operating temperature in the time expected by the DME.
- Engine Running Too Cool: Because the thermostat is stuck open, coolant is always circulating through the radiator. This makes it take a very long time for the engine to warm up, and it may never reach its proper operating temperature, especially in colder weather or during short drives.
- Poor Fuel Economy: An engine that runs too cool stays in its warm-up fuel map, which uses more gasoline. You may notice a significant drop in your miles per gallon.
- Reduced Cabin Heat: The heating system in your car uses hot coolant to warm the cabin. If the engine isn't getting hot enough, your heater may only blow lukewarm air.
Is There a Recall on the M5 Thermostat?
No, there are no active safety recalls from the National Highway Traffic Safety Administration (NHTSA) for the engine coolant thermostat specifically for the 2006-2011 BMW M5. BMW has issued warranty extensions and service actions for thermostats on other models like those with N63 and N20 engines, but these do not apply to the S85 engine in the M5. Always verify with a dealer, but as of now, replacement is a standard repair.
Choosing the Right Aftermarket Thermostat
Because replacing the thermostat on the S85 engine is labor-intensive, choosing a quality part is critical. The job requires removing the intake plenums, which takes several hours. 🎬 See this guide on how to remove the intake plenums. Using a low-quality part that fails early will mean paying for that expensive labor all over again.
OEM vs. Aftermarket Quality
For a complex, electronically controlled part on a high-performance engine like the S85, the consensus among experienced BMW mechanics and owners is to use the Original Equipment Manufacturer (OEM) part or a trusted OEM supplier. Aftermarket parts can sometimes fail to communicate properly with the DME, leading to persistent fault codes even after replacement.
| Tier | Brands | Quality & Notes |
|---|---|---|
| Tier 1: OEM / OEM-Equivalent | Genuine BMW, Mahle/Behr | Mahle-Behr is the original manufacturer for BMW. Choosing either Genuine BMW or Mahle ensures perfect fit, function, and reliability. This is the safest and most recommended option to avoid compatibility issues. The standard opening temperature is 79°C. |
| Tier 2: Reputable Aftermarket | Calorstat, Beck Arnley, Gates | Calorstat by Vernet is a known OEM supplier for many European brands and is a solid choice. Beck/Arnley often sources and re-packages OE-quality parts for specific applications, making them a generally reliable option. Gates is a well-known brand; they offer a "performance" thermostat for the M5 that opens at a lower temperature (71°C), which some owners might choose for modified or track-focused cars, but it is not the standard specification. |
| Tier 3: Budget Options | Motorad | Motorad is a large manufacturer, but owner reviews are mixed. Some have used them without issue, while others report premature failures, sometimes in under a year. Given the high labor cost for this specific job, using a budget-tier part is a significant risk. |
Pro Tip: While you are replacing the thermostat, it is highly recommended to also replace the two small plastic coolant pipes that connect to the thermostat housing and their O-rings. These can become brittle and are prone to leaking. It's a small additional cost that can prevent a future coolant leak.
Frequently Asked Questions (FAQ)
How difficult is it to replace the M5 thermostat?
This is an advanced DIY job. The main difficulty is the need to remove the large intake plenums that cover the top of the engine to gain access to the thermostat housing below. It requires patience, the right tools (including various extensions and sockets), and careful tracking of bolts and hoses. For most owners, this job is best left to a qualified independent BMW specialist or a dealership.
🎬 Watch: A complete walkthrough of the S85 thermostat replacement procedure.What is the typical cost to replace the thermostat?
The part itself can range from under $40 to over $120. However, the majority of the cost is labor. An independent shop may charge between $500 and $800 in labor due to the time it takes to remove and reinstall the plenums. Dealership pricing will likely be higher.
What does the 2B59 fault code mean?
The 2B59 code means "Coolant Thermostat Monitor." The engine's computer (DME) expects the engine to reach a certain temperature within a set amount of time after starting. When the thermostat is stuck open, the engine warms up too slowly, and the DME logs this fault. It's a very reliable indicator of a failed thermostat.
🎬 Watch: Solving the 2B59 fault code on your V10.Should I use a lower temperature thermostat?
Some brands like Gates offer a 71°C thermostat instead of the 79°C OEM spec. While a lower temperature might be beneficial for highly modified or dedicated track cars, it can cause the engine to run slightly cooler than intended for daily driving. This may impact fuel efficiency and long-term performance as designed by BMW. For a stock or daily-driven M5, sticking with the OEM 79°C temperature is the recommended path.
Helpful Videos
Technical Specifications
OEM Part Numbers: 11537836155
The OEM specification for the thermostat is an electronically controlled unit with an opening temperature of 79° Celsius (174° Fahrenheit).
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.
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