Mercedes-Benz CL600 Engine Coolant Temperature Sensor Guide (1998-2014)
A failing coolant temperature sensor in your CL600 can cause everything from bad gas mileage to a check engine light.
- A bad ECT sensor commonly causes a check engine light, poor fuel economy, and black exhaust smoke.
- The sensor location varies by engine: it's easier to access on the early M137 V12 but very difficult on the later M275 V12.
- For best results, choose an OEM-quality aftermarket brand like Delphi or Febi, as sensor accuracy is critical for the CL600's V12 engine.
- There are no active recalls or TSBs specifically for the coolant temperature sensor on this vehicle.
Is Your CL600 Running Rough or Getting Poor Fuel Economy?
The V12 engine in your 1998-2014 CL600 is a complex machine that relies on precise data to run smoothly. A faulty Engine Coolant Temperature (ECT) sensor can throw a wrench in the works, leading to noticeable problems. Because this sensor influences so many engine functions, the symptoms of failure can be varied and sometimes confusing. Ignoring them can lead to poor performance, failed emissions tests, and potentially more expensive repairs down the road.
Symptoms of a Bad Coolant Temperature Sensor
When the ECT sensor starts to fail, it sends incorrect signals to the engine computer. This can make your CL600 behave unpredictably. Here are the most common signs to watch for:
- Check Engine Light: This is often the first warning. A scan tool will likely show codes like P0115, P0117, or P0118.
- Poor Fuel Economy: If the sensor tells the computer the engine is always cold, the computer will enrich the fuel mixture, wasting gas.
- Black Smoke from Exhaust: A very rich fuel mixture can result in unburned fuel exiting through the exhaust, appearing as black smoke.
- Engine Overheating or Inaccurate Gauge: The sensor might cause the temperature gauge on your dash to read incorrectly, or it may fail to trigger the cooling fans when needed, leading to actual overheating.
- Rough Idle and Poor Performance: With incorrect fuel and timing adjustments, the engine can idle poorly, hesitate, or feel sluggish.
- Hard Starting: The engine may be difficult to start, especially when it's already warm, because the computer is using the wrong fuel mixture for the conditions.
Generation-Specific Issue: Sensor Location
The location of the ECT sensor, and therefore the difficulty of replacement, differs between CL600 generations.
For the 1998-2002 C215 models with the M137 V12 engine, the sensor is often located at the front of the engine near the thermostat housing, making it more accessible.
For the 2003-2014 C215 and C216 models with the M275 V12 Bi-Turbo engine, the sensor is located at the rear of the left cylinder head. This position is extremely difficult to reach and may require significant labor to access.
Choosing the Right Aftermarket Sensor for Your CL600
For a critical sensor like the ECT, quality and accuracy matter. While a Genuine Mercedes-Benz part is always an option, several reputable aftermarket brands offer reliable alternatives at a lower price. Here’s a breakdown of available brands to help you choose.
Tier 1: OEM-Quality Brands
These brands are often Original Equipment (OE) suppliers to Mercedes-Benz and other German automakers. They are known for high-quality engineering and are a trusted alternative to the dealer part.
- Delphi: With a long history as an OE supplier, Delphi parts are known for quality and reliability.
- Febi: Febi Bilstein is a well-regarded German brand that produces OE-quality replacement parts. Many professional mechanics trust Febi for European vehicles.
- Vemo: Another brand specializing in European car parts, often considered to be of OE quality.
Tier 2: Reputable Aftermarket Brands
These are established brands with a solid reputation for producing dependable parts, though they may not be direct OE suppliers.
- Standard Ignition (Intermotor): A major player in the aftermarket sensor world, known for consistent quality.
- Facet: An Italian brand that produces a wide range of electronic components and is a viable replacement option.
Tier 3: Economy Brands
These brands offer the most budget-friendly prices. They can be a good choice for a quick repair, but may not have the same long-term durability or precise calibration as higher-tier options.
- URO Parts: A popular budget alternative for European car parts, offering a wide range of components.
- Walker Products, Four Seasons, True Tech, CRP: These brands provide functional, low-cost replacements for a variety of applications.
Engine Coolant Temperature Sensor Cost for 1998-2014 CL600
| Part Type | Price Range |
|---|---|
| New Aftermarket | $8.23 - $86.48 |
| New OEM (Genuine Mercedes-Benz) | $60 - $190 |
| Shop Labor | $150 - $600 |
Frequently Asked Questions (FAQ)
Where is the coolant temperature sensor located on my CL600?
It depends on your engine. On earlier C215 models (approx. 1998-2002) with the M137 engine, it is typically at the front of the engine near the thermostat housing. On later C215 and all C216 models (approx. 2003-2014) with the M275 engine, it is at the rear of the left cylinder head, which is much harder to access.
Can I replace the ECT sensor myself?
If the sensor is located at the front of the engine, a DIY replacement is very feasible with basic tools. However, if it is at the rear of the engine, the job is significantly more difficult due to the tight space and may be best left to a professional mechanic.
What happens if I don't replace a bad coolant sensor?
Continuing to drive with a bad sensor can lead to persistently poor fuel economy, rough running, and potential engine damage from overheating if the cooling fans don't operate correctly. It will also cause your vehicle to fail an emissions inspection.
Are there any recalls for the CL600 coolant temperature sensor?
No, as of early 2026, there are no specific NHTSA recalls or Technical Service Bulletins (TSBs) for the engine coolant temperature sensor on the 1998-2014 Mercedes-Benz CL600.
Technical Specifications
OEM Part Numbers: 0005425118 0115425117 0999053800 2219055600
Typically a 2-pin, clip-in style thermistor sensor. The specific part number can vary by production year and engine type (M137 vs. M275).
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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.
- Mercedes-Benz CL600:
- 🛍️ Shop This Part
- Is Your CL600 Running Rough or Getting Poor Fuel Economy?
- Symptoms of a Bad Coolant Temperature Sensor
- Generation-Specific Issue: Sensor Location
- Choosing the Right Aftermarket Sensor for Your CL600
- Tier 1: OEM-Quality Brands
- Tier 2: Reputable Aftermarket Brands
- Tier 3: Economy Brands
- Engine Coolant Temperature Sensor Cost for 1998-2014 CL600
- Frequently Asked Questions (FAQ)
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