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A properly functioning thermostat keeps your Mercedes-Benz E-Class engine at the right temperature for performance, fuel efficiency, and cabin comfort. If the thermostat sticks open or closed, you can see symptoms ranging from poor heater output to engine overheating, so choosing the correct replacement matters.This guide highlights seven shortlisted thermostats that fit this vehicle and explains the evaluation criteria used, such as fitment accuracy and temperature response. Continue for a clear, practical overview to help you pick the right unit for safe, consistent operation.
Looking for other parts? See all Mercedes-Benz E-Class parts & accessories.
Top Picks at a Glance
| Best overall The best all-around choice for most situations | TRQ Thermostat with Housing Assembly for Mercedes-Benz |  |
| Best quality Built to a higher standard if you want something more solid | Mishimoto Racing Thermostat for Mercedes‑Benz E55 AMG (2003–2006) |  |
| Best Value The sweet spot between price and what you get | Mercedes-Benz Engine Coolant Thermostat Kit (112 203 02 75) |  |
| Best Budget The cheapest option that still gets the job done reliably | MotoRad 458-192 Integrated Thermostat Housing (192°F) |  |
| Highest Rated A top-rated pick with lots of positive feedback | NewYall Engine Coolant Thermostat Housing with Gasket for Mercedes 550/450 Series |  |
| Most Popular A crowd favorite that many people choose with confidence | ROADFAR Thermostat Housing Assembly for Mercedes-Benz (fit list) |  |
| Best Seller A high-volume bestseller chosen again and again | A-Premium Thermostat Housing Assembly with Gasket for Mercedes-Benz |  |
1. TRQ Thermostat with Housing Assembly for Mercedes-Benz
| Material | Aluminum |
|---|---|
| Gasket Or Seal Included | Yes |
| Opening Temperature | 100 Deg. C / 212 Deg. F |
This TRQ thermostat with housing is a pre-assembled replacement meant to swap directly into compatible Mercedes-Benz engines without modification. It combines an aluminum housing, integrated gasket, and a thermostat calibrated to open at 100 C (212 F), so it restores proper engine temperature regulation and helps prevent overheating when the original unit ages or leaks. Typical use is a DIY or shop-level repair when the OEM thermostat or plastic housing has warped or started to leak; the machined aluminum housing is more durable than common plastic originals and comes with reference numbers to match fitment. Practical benefits include easier installation because the assembly arrives complete and likely reduced repeat repairs versus fragile plastic housings. Important limitations are mixed quality control reported by some buyers and occasional returns for defective or used-seeming parts, so inspect the unit and sealing surfaces before install and be prepared to source replacement O-rings or bolts if fitment differs from the factory fasteners.
Best for: Buyers seeking a balanced, reliable factory-quality replacement for Mercedes-Benz E-Class cooling systems who value a straightforward, pre-assembled swap that reduces shop time.
Less Ideal for: If you prioritize a lifetime warranty or strictly OEM-sourced parts from a dealer, consider manufacturer-sourced options instead.
- Direct-fit assembly that replaces the thermostat and housing together for faster installation
- Aluminum machined housing is more durable than many factory plastic housings
- Includes gasket and is pre-assembled to reduce installation steps
- Thermostat calibrated to open at 100 C (212 F), matching expected operating temperature range
- Some buyers reported receiving defective or used-feeling units requiring returns
- May require different bolts or minor hardware not included if replacing a plastic original
Verdict: A sturdy, pre-assembled thermostat and housing that makes a practical, time-saving replacement for Mercedes-Benz E-Class cooling repairs, but inspect for quality on arrival.
2. Mishimoto Racing Thermostat for Mercedes‑Benz E55 AMG (2003–2006)
| Specific Uses For Product | Racing, Track Use |
|---|---|
| Additional Features | Lower Activation Temperature |
| Material Type | Stainless Steel |
| Controller Type | Mechanical knob |
This Mishimoto racing thermostat replaces the factory unit in 2003–2006 Mercedes‑Benz E55 AMG engines and opens at a lower temperature to let coolant circulate earlier than stock. It is used as a direct swap for the M113 5.4L supercharged engine to reduce and stabilize operating temperatures during spirited driving or track sessions. Notable features include a lower activation temperature (167°F versus the stock 180°F), a stainless steel construction, and a mechanical design that requires no electrical controls. The practical benefits are cooler steady‑state temps under load, reduced risk of heat soak, and a factory‑style fit intended for straightforward installation. Limitations are that the fixed lower activation point may require complementary adjustments to fan trigger settings or engine management for ideal results, and some owners report minor housing modification is needed on non‑supercharged engines for fitment. This is a focused performance upgrade for drivers who want a simple, reliable way to lower operating temperatures without complex electronics.
Best for: Performance‑oriented Mercedes‑Benz E‑Class owners who prioritize lower operating temperatures on street and track and prefer a simple mechanical upgrade to improve cooling efficiency.
Less Ideal for: Drivers seeking adjustable electronic temperature control or those unwilling to make minor wiring or housing adjustments should consider other cooling solutions.
- Lower activation temperature (167°F) reduces and stabilizes engine temperatures under load.
- Direct replacement form intended for clean fitment on the specified E55 AMG engine.
- Stainless steel construction with a mechanical design for durability and no electrical failure modes.
- Lifetime warranty backing from the manufacturer.
- Fixed lower opening temperature may require adjusting fan triggers or ECU settings to fully realize benefits.
- Fitment notes indicate slight thermostat housing modification may be necessary on some non‑supercharged engines.
Verdict: A simple, durable racing thermostat that lowers the opening temperature for the 2003–2006 E55 AMG to help keep engine temps down during performance driving.
3. Mercedes-Benz Engine Coolant Thermostat Kit (112 203 02 75)
| Manufacturer | Mercedes-Benz |
|---|---|
| Item model number | 112-203-02-75 |
| Manufacturer Part Number | 112 203 02 75 |
This is a genuine Mercedes-Benz thermostat housing kit supplied as a direct factory replacement for affected Mercedes engines. It installs in place of the original housing and includes the thermostat, so it restores the engine's ability to reach and maintain proper operating temperature and eliminates P0128-type running issues. Typical use is a routine cooling-system repair when the thermostat or housing is leaking, corroded, or stuck; several owners report straightforward installs and return to normal cabin heat and engine temperature. The factory fit reduces fitment headaches and the integrated gasket design speeds installation. The main limitations are that it is a vehicle-specific OEM part so it only fits certain Mercedes engines and buyers should verify fitment before ordering, and as an OEM part it may cost more than aftermarket alternatives despite the value in avoiding compatibility problems.
Best for: Practical optimizers who prioritize keeping their Mercedes E-Class running to factory standards and want a straightforward, no-surprises repair using a factory replacement part.
Less Ideal for: Buyers seeking the lowest possible upfront cost or universal aftermarket replacements should consider aftermarket options instead of a factory thermostat kit.
- Genuine Mercedes-Benz factory replacement for correct fit and function
- Includes thermostat and integrated gasket to simplify installation
- Reportedly fixes temperature and P0128 issues when original unit fails
- Many users report easy installation with minimal disassembly
- Only fits specific Mercedes-Benz engines and model years so fitment must be confirmed
- Higher cost compared with generic aftermarket thermostat housings
Verdict: A factory Mercedes thermostat housing kit that restores correct engine temperature control and simplifies installation, best for owners who value OEM fit and reliability over the cheapest option.
4. MotoRad 458-192 Integrated Thermostat Housing (192°F)
| Part Number | 458-192 |
|---|---|
| Opening Temperature | 192°F |
| Material Type | Copper |
| Fits Vehicles | Select Mercedes-Benz models |
The MotoRad 458-192 is an integrated thermostat housing intended as a budget-friendly replacement for select Mercedes-Benz cooling systems. It combines the thermostat and housing into one copper-bodied assembly that installs in place of the factory unit and is listed to open at 192°F. Typical use is a straightforward swap when the original housing leaks or the thermostat fails; the integrated design reduces parts and install steps compared with separate thermostat replacements. Reviewers report solid fitment and simple installation on compatible Benz models, and the copper construction gives a traditional, durable feel. Some users have reported early failures or that the unit omitted a temperature sensor present on some factory housings, so verify your car's sensor requirements before ordering. This part aims to provide a low-cost, OEM-replacement-style option for drivers who need a working thermostat housing without paying dealer prices, but buyers should be prepared to confirm fitment and inspect for the required sensor provisions during installation.
Best for: Budget-conscious Mercedes-Benz E-Class owners who need a low-cost, factory-replacement-style thermostat housing and prioritize immediate affordability over premium aftermarket features.
Less Ideal for: Owners who require an exact factory sensor-equipped assembly or who prioritize the longest-term reliability and extended performance warranties should consider higher-end or dealer-sourced units instead.
- Integrated housing and thermostat simplifies installation and reduces parts to buy.
- Lists direct replacement part number and fitment for many Mercedes-Benz models for easier compatibility checks.
- Copper material offers traditional thermal conductivity and a sturdy feel.
- Limited lifetime warranty listed by the manufacturer.
- May not include the engine temperature sensor that some Mercedes engines require.
- Some customers reported premature failures or the thermostat sticking, indicating variable long-term reliability.
Verdict: A cost-effective integrated thermostat housing that offers direct-fit replacement for many Mercedes-Benz models at a budget-friendly price.
5. NewYall Engine Coolant Thermostat Housing with Gasket for Mercedes 550/450 Series
| Brand | NewYall |
|---|---|
| Item model number | 27220005l5 |
| Manufacturer Part Number | 27220005l5 |
| Compatible models | Mercedes CL550, E550, G550, GL450, GL550, ML550, S550, SL550 (years listed in description) |
This NewYall thermostat housing replaces the factory unit on many Mercedes 550 and 450 series vehicles and includes a replacement gasket for a complete seal. It mounts in place of the original housing and routes coolant and the thermostat sensor where the factory part did, so installation is typically a straightforward swap for technicians or experienced DIYers. Customers report good fit and function on E550, S550, GL450 and similar models, with the part addressing stuck-open thermostat symptoms and restoring normal warm-up and heater performance. The included gasket and what buyers describe as a factory-like fit reduce the chance of leaks when installed correctly, but a few reports note early failures on some cars and fitment differences on certain model years, so confirm exact fit before installation. This is a practical repair option when you need a cost-effective replacement that gets the cooling system back to normal without sourcing an expensive factory part.
Best for: Reliability-focused owners looking for an affordable, direct replacement part to restore correct engine temperature control and avoid repeated thermostat-related failures.
Less Ideal for: Buyers seeking guaranteed long-term factory-spec longevity or those unwilling to verify model-year fitment should consider OEM or dealer-sourced replacements instead.
- Includes replacement gasket for a sealed installation
- Fits a broad range of Mercedes 550 and 450 series model years listed in the description
- Reports of straightforward installation and factory-like fit reduce installer time
- Addresses common thermostat failures such as stuck-open thermostat symptoms
- Some users reported premature failure on certain vehicles after several months
- A few reviews indicate fitment differences on specific model years requiring modifications
Verdict: A budget-friendly replacement housing that restores thermostat function on many Mercedes 550/450 models with an included gasket for a ready-to-install repair.
6. ROADFAR Thermostat Housing Assembly for Mercedes-Benz (fit list)
| Brand Name | ROADFAR |
|---|---|
| Included Components | Thermostat Housing Assembly |
| Specific Uses For Product | Automotive engine temperature control |
| Mounting Type | Engine Block Mount |
This ROADFAR thermostat housing assembly replaces the factory water outlet and integrated thermostat on compatible Mercedes‑Benz E‑Class and related models to stop leaks and help the cooling system maintain correct operating temperature. It is supplied as a direct replacement assembly so mechanics or competent DIYers can swap it in place of a failed housing and thermostat without major modification. Notable features in the listing include metal construction, engine‑block mounting design, and delivery as a complete thermostat housing assembly rather than a bare thermostat valve, which simplifies installation and sealing. Practical benefits are straightforward fitment to the vehicles listed, immediate restoration of coolant routing and thermostat function, and fewer separate parts to manage during the job. Limitations are that fitment must be checked carefully against the vehicle application before ordering and professional installation is recommended for confined engine bays or when electrical connectors are present; some buyers also reported occasional fitment confusion so verify part numbers during selection.
Best for: Convenience‑minded Mercedes‑Benz owners who prioritize a straightforward, drop‑in replacement to fix leaks or thermostat failures without sourcing multiple components or complex parts.
Less Ideal for: Those seeking an exact cosmetic match to factory surfaces or buyers unwilling to verify vehicle fitment and part numbers should consider alternatives or dealer parts.
- Supplies a full thermostat housing assembly so you replace the housing and thermostat in one step
- Metal construction suitable for engine bay service
- Listed to fit a wide range of Mercedes‑Benz models in the product fitment list
- Designed for engine‑block mounting to match factory installation and sealing
- Fitment can be inconsistent so buyers must confirm compatibility carefully before purchase
- Appearance and finish are utilitarian rather than factory‑level cosmetic match
Verdict: A ready‑to‑install thermostat housing assembly that simplifies replacing a leaking or failed thermostat on supported Mercedes‑Benz E‑Class and related models.
7. A-Premium Thermostat Housing Assembly with Gasket for Mercedes-Benz
| Brand | A-Premium |
|---|---|
| Manufacturer Part Number | APTHA0053 |
| OEM Part Number | 902-5912, 85999, 34704, 2722000115, 2722000415, 9025912 |
| Vehicle Fitment | Select Mercedes-Benz C/CLK/E/GLK/ML/SLK/SL/GL ranges (see listing) |
| Date First Available | April 2, 2022 |
This A-Premium thermostat housing assembly replaces the factory unit on many Mercedes-Benz E-Class and related models and comes as a complete kit with the thermostat, gasket, housing, and sensor. It is installed in the engine cooling circuit to regulate coolant flow and maintain correct operating temperature. The assembly is intended for direct-fit replacement when the original housing has failed or is leaking and is typically installed by a professional or experienced DIYer following a coolant system drain and careful surface cleaning. Notable features include the included gasket and sensor which reduce the need to source separate parts and the seller-stated hardness and crushing tests that aim to ensure reliable sealing. Practical benefits are straightforward: a one-part replacement that restores thermostat function and reduces coolant leaks when mounted correctly. Limitations to consider are that fitment must be verified against reference numbers and some buyers reported mixed results, so careful inspection during installation and testing for leaks after the thermostat cycles are advisable.
Best for: Risk-averse mainstream buyers who prioritize a straightforward, one-piece replacement that restores factory cooling function with minimal parts sourcing and who prefer to avoid complex upgrades.
Less Ideal for: Those seeking higher-performance or upgraded thermostat solutions for tuned engines or heavy-duty cooling modifications should consider performance-specific parts instead.
- Complete kit includes thermostat, housing, gasket and temperature sensor for convenience.
- Marketed as a direct replacement for specified Mercedes-Benz models, simplifying part selection.
- Seller reports durability testing aimed at reliable sealing and heat dissipation.
- Contains the necessary gasket to reduce risk of immediate leaks after installation.
- Fitment varies by model year and reference number so verification is required before purchase.
- Some customers reported installation or performance issues requiring replacement parts or professional rework.
Verdict: A convenient, all-in-one thermostat housing assembly intended to restore proper cooling system function on compatible Mercedes-Benz E-Class and related models.
Choosing the Right Mercedes-Benz E-Class Thermostat: Key Factors to Consider
Fitment and Part Number Accuracy
Exact fitment is critical because the thermostat must match the E-Class coolant passages and mounting points to seal correctly and operate as intended. Incorrect fitment can lead to installation difficulty, coolant leaks, or improper flow that affects engine temperature.
Checking the part number fitment ensures the replacement matches the original opening temperature and physical dimensions. Confirming bolt pattern, flange orientation, and housing interface before purchase reduces the chance of a return and helps maintain factory cooling system geometry.
Opening Temperature and Temperature Response
The thermostat's opening temperature determines when coolant begins to circulate through the radiator and directly affects engine warm-up and cabin heating. A thermostat that opens too early can cause the engine to run cold, reducing efficiency, while one that opens too late can cause overheating.
Temperature response refers to how quickly the valve transitions from closed to open around the rated temperature. A consistent and predictable response helps avoid erratic temperature swings during mixed driving conditions, improving drivability and emissions control.
Seal and Housing Interface Quality
The seal between the thermostat and housing must resist coolant pressure, temperature cycling, and chemical exposure from antifreeze. A poor seal can lead to a thermostat housing seal leak, which may cause coolant loss and overheating.
Look for thermostats with robust sealing materials and well-machined mating surfaces to reduce the likelihood of leaks. Proper compression and even gasket contact help ensure a durable, maintenance-free installation.
Material Durability and Corrosion Resistance
Thermostats operate in a harsh environment of hot coolant and varying pressures, so materials must resist corrosion and degradation over time. Metal components should resist pitting and gasket materials should withstand prolonged exposure to coolant additives.
Choosing a thermostat built from corrosion-resistant metals and high-quality elastomers helps prevent premature failure and reduces the risk of parts seizing or seals degrading, which would otherwise lead to leaks or stuck valves.
Ease of Installation and Compatibility with Cooling System
A design that mirrors the original equipment makes installation straightforward and reduces the chance of errors during replacement. Features like clear orientation markings and integrated sealing surfaces speed up the job and minimize the need for additional parts.
Compatibility with the E-Class cooling system also means the thermostat does not obstruct coolant flow or interfere with sensors. Consider whether the unit requires any special tools or additional gaskets, and aim for options that simplify replacement while maintaining proper coolant circulation.
Reliability Under Operating Conditions
Thermostats must withstand repeated thermal cycles and maintain consistent operation across a range of ambient temperatures and driving loads. Reliability matters because a failing thermostat can cause overheating or extended cold running periods, each of which can harm engine components.
Assess expected lifespan, manufacturer quality control, and evidence of consistent performance in similar vehicles when possible. Reliable units reduce the frequency of repairs and help ensure steady engine temperature management over time.
How We Chose the Best Mercedes-Benz E-Class Thermostat
We selected thermostats that meet the tight fitment and performance tolerances required by Mercedes-Benz E-Class engines. Our editorial filters prioritized exact part number fitment, reliable temperature regulation at the specified opening point, and durable materials for long-term sealing and corrosion resistance. We also considered the quality of the thermostat housing interface and the robustness of the seal to reduce the risk of leaks, plus compatibility with the vehicle's coolant pathways to avoid flow restriction.In our screening we excluded universal or generic thermostats without documented fitment for the E-Class and units that lack manufacturer opening temperature data. We favored products with clear technical specifications, solid construction, and evidence of proper manufacturing controls. The final list balances mechanical reliability, installation practicality, and the ability to restore proper engine operating temperature under normal driving conditions.
Our full evaluation process is outlined in our review methodology.
FAQ
What are common signs of a bad thermostat in a Mercedes-Benz E-Class?
Common signs often include fluctuating engine temperature, poor cabin heat, and the engine running too hot or too cold. You may also notice heater performance decline or coolant leaks near the thermostat housing. These symptoms usually indicate the valve is not opening or sealing properly.
How can I test a thermostat without removing it?
You can monitor engine temperature behavior and heater output to look for abnormal patterns, which often point to thermostat issues. Some owners use an OBD-II scan tool to observe coolant temperature readings while the engine warms up. These checks give useful clues but are not a complete substitute for a bench or in-vehicle test with the thermostat removed.
Will a leaking thermostat housing cause overheating?
A thermostat housing seal leak can reduce coolant level and pressure, which may contribute to overheating if left unaddressed. Leaks also let air into the cooling system, which can cause hot spots and inconsistent temperature readings. Addressing the leak and ensuring proper sealing helps restore stable cooling system performance.
What causes an engine to run cold after thermostat replacement?
An engine running cold after a replacement often indicates an incorrect opening temperature or a thermostat stuck open. It can also result from incorrect installation that alters coolant flow. Verifying the correct part number and proper installation usually resolves persistent cold-running conditions.
How long does a thermostat typically last in normal driving?
Thermostat lifespan varies by material quality and operating conditions, but they commonly last several years under typical use. Exposure to coolant degradation, severe thermal cycling, or corrosion can shorten service life. Routine inspection during coolant service intervals helps detect issues early.
Do I need to replace the gasket or seal when changing the thermostat?
Replacing the gasket or seal is usually recommended because old seals can become brittle or deformed and may not reseal reliably. Installing a new gasket helps ensure a proper seal at the thermostat housing and reduces the chance of leaks after the job is complete.
Conclusion
Prioritize exact fitment, the correct opening temperature, and a durable seal when choosing a thermostat for a Mercedes-Benz E-Class. These factors have the biggest impact on restoring consistent engine operating temperature and reliable heater performance.Expect tradeoffs between ease of installation and long-term durability. Focus on parts that match the vehicle's specifications and show solid construction to minimize future cooling system issues.
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- Check out all Mercedes-Benz E-Class parts & accessories
- Explore Thermostats Maintenance & Repair Guides
- Explore Cooling System
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