DUCATI 55340031A Coolant Thermostat Sensor Thermo Switch 851 748 916 996 998
fits model: St2, St4s, St4. make: Ducati.
( Manufacturer Part Number: 55340031A ), ( Part Type: Switch Thermostat Sensor )
Review DUCATI 851 748 916 996 998 Coolant Thermostat Sensor Thermo Switch fits ST2 ST4S ST4
The **Ducati 55340031A 851/748/916/996/998 ST2/ST4S Coolant Thermostat Sensor/Thermo Switch (ST4)** is a precision-engineered component designed exclusively for Ducati s high-performance V-twin motorcycles, ensuring optimal thermal management and reliable operation under demanding riding conditions. This thermostat sensor, identified by its unique part number, plays a critical role in maintaining the engine s operating temperature within the ideal range, balancing efficiency, power delivery, and longevity. Crafted from high-grade materials, it integrates a temperature-sensitive bimetallic element that responds dynamically to coolant temperature fluctuations, regulating the flow through the engine s cooling system with exceptional accuracy. The ST4 variant, in particular, is tailored for Ducati s ST2 and ST4S models, which feature advanced cooling architectures, ensuring seamless compatibility with the bike s electronic engine management system (EMS) and throttle-by-wire setup. This sensor not only monitors the coolant temperature but also serves as a critical feedback mechanism for the bike s ECU, enabling precise adjustments to fuel injection, ignition timing, and cooling fan operation to prevent overheating or inefficient combustion. Built to withstand the extreme thermal and mechanical stresses of high-performance riding, the thermostat sensor is sealed with a durable gasket and features a robust mounting design that minimizes leakage and ensures long-term reliability. Whether used in track-focused applications or daily commuting, this component is essential for preserving the engine s performance, protecting internal components from thermal damage, and maintaining Ducati s signature blend of power and precision. For riders seeking to restore or upgrade their bike s cooling system, this thermostat sensor represents a direct-fit, OEM-quality solution that upholds the brand s reputation for engineering excellence.
### **Pros and Cons of Buying a Ducati 553 (Model Years 2003 2008) with Specific Thermostat/Sensor Issues (ST2, ST4, ST4S, etc.)**
#### **Pros**
1. **Iconic Design and Prestige**
The Ducati 553 (part of the 851/996/998/ST2/ST4/ST4S lineage) is a legendary motorcycle known for its aggressive, timeless styling. It carries Ducati s reputation for high-performance Italian engineering, making it a desirable collector s item or a statement bike.
2. **V-Twin Engine Heritage**
The 944cc L-twin engine is a classic, producing around **100 110 hp** (depending on tuning and model year). It offers a deep, throaty exhaust note and a smooth power delivery, especially when properly maintained. The engine is robust if cared for, with a strong aftermarket support base for upgrades.
3. **Reliability (When Well-Maintained)**
Ducati s air-cooled V-twin engines from this era are known for longevity if they receive regular servicing. Many examples with **under 10,000 miles** or **low hours** can still run strong, provided the owner has kept up with oil changes, valve adjustments, and minor wear-and-tear items.
4. **Strong Aftermarket and Customization Potential**
The Ducati 553 (and its variants) has a dedicated aftermarket, with options for **exhaust upgrades, carburetor tuning, engine swaps (e.g., 1098cc or 1100cc), and suspension modifications**. The bike s frame and chassis are also popular for **chopper, bobber, or caf racer builds**.
5. **Resale Value for Classic Models**
Certain variants (e.g., **ST2, ST4, or limited-edition models**) hold value well, especially if they are in good condition. The **2003 2008 models** are now considered "classic" Ducatis, appealing to enthusiasts who appreciate vintage Italian bikes.
6. **Riding Experience**
The 553 offers a **leaning, aggressive posture** and a **direct, responsive throttle**, making it fun for both cruising and spirited riding. The **single-sided swingarm and rear monoshock** provide a sporty feel, though handling is not as precise as modern Ducatis.
7. **Lower Running Costs (Compared to Modern Ducatis)**
Fuel injection was introduced in later models (e.g., **998, 1000SS**), but the **carbureted 996/ST2/ST4** versions are cheaper to maintain. Parts are widely available, and labor costs are lower than for newer Ducatis.
---
#### **Cons**
1. **Thermostat/Sensor Issues (ST2, ST4, ST4S Problems)**
- The **thermostat and temperature sensors** in these models (especially the **ST2, ST4, and ST4S**) are notorious for failing, leading to **overheating, poor cooling, or false temperature readings**.
- Common symptoms include:- **Engine running hot** (even at idle).
- **Check engine light (CEL) due to faulty O2 sensors or coolant temperature sensors**.
- **Poor fuel economy or rough idle** from incorrect air-fuel ratios.
- **Replacement parts can be expensive**, and some sensors are **hard to source** (especially for older ST models).
- **DIY replacement is possible but requires careful wiring and calibration checks.**
2. **Electrical Reliability Problems**
- Ducati s **early 2000s wiring harnesses** are prone to **corrosion, loose connections, and sensor failures**.
- The **ECU (if equipped)** can be finicky, requiring **reprogramming or replacement** if damaged.
- **Alternator and regulator issues** are common, leading to **battery drain or voltage fluctuations**.
3. **Maintenance Intensity**
- Ducati s **air-cooled engines** require **regular valve adjustments** (every **10,000 15,000 miles**).
- **Oil changes must be done frequently** (every **3,000 5,000 miles** with synthetic oil) to prevent sludge buildup.
- **Carburetor tuning** (if not fuel-injected) can be **fussy**, requiring periodic adjustments.
- **Brake system wear** (especially on older models) can be significant, with **front discs and calipers** needing frequent replacement.
4. **Handling Limitations**
- The **rigid frame and rear monoshock** make the bike **less forgiving on rough roads** compared to modern Ducatis with **parallelogram forks and adjustable suspension**.
- **Cornering stability** is decent but not as refined as later models (e.g., **1098, 1199 Panigale**).
- **Weight distribution** (heavier rear due to the engine) can make **high-speed stability** less predictable.
5. **Fuel Injection vs. Carburetion Trade-offs**
- **Carbureted models (996, ST2, ST4)** are **cheaper to maintain** but require **more tuning effort** for optimal performance.
- **Fuel-injected models (998, 1000SS, ST4S)** are **more reliable in cold weather** and **easier to start**, but **fuel system issues (injectors, pumps) can be costly to repair**.
- **Aftermarket fuel injection kits** (e.g., **Walbro, Morimoto**) are an option for carbureted models but add complexity.
6. **Parts Availability and Cost**
- While **common parts are widely available**, **rare or OEM components (e.g., specific sensors, gaskets, or wiring harnesses)** can be **expensive or hard to find**.
- **Labor costs** for Ducati work can be high, especially in specialized shops.
- **Replacement engines or major components** (e.g., **crankshaft, camshafts**) are **not cheap** if the original fails.
7. **Environmental and Noise Considerations**
- The **loud exhaust note** (especially on carbureted models) may **violate noise laws** in some areas.
- **Emissions compliance** (if applicable) can be an issue for older models in regions with strict regulations.
- **Fuel economy** is **poor by modern standards** ( **35 45 mpg**), making it expensive to run.
8. **Potential Hidden Damage**
- Many older Ducatis have **frame cracks** (especially in the **rear subframe area**) due to **stress from high-speed riding or poor welding**.
- **Rust** (common in **suspension components, swingarm, and exhaust**) can weaken structural integrity.
- **Previous accident damage** (e.g., **bent frame, warped engine mounts**) is common and **expensive to repair properly**.
---
### **Ending Conclusion**
Buying a **Ducati 553 (2003 2008) with thermostat/sensor issues (ST2, ST4, ST4S, etc.)** can be a **great investment for the right buyer**, but it requires **careful consideration of maintenance costs, reliability risks, and personal riding needs**.
- **Best for:** Enthusiasts who **love classic Ducatis**, enjoy **tinkering with mechanicals**, and are willing to **budget for repairs**. Ideal for **weekend riders, collectors, or those building custom bikes**.
- **Not ideal for:** **Daily commuters, those seeking modern reliability, or buyers who want a "plug-and-play" experience**. Also **not suitable for riders in areas with strict emissions or noise laws**.
If you **find a well-documented example with a clean service history**, **low mileage/hours**, and **proven thermostat/sensor replacements**, it can be a **fantastic project bike**. However, if you **prioritize convenience and modern reliability**, a **newer Ducati (e.g., 1299 Panigale, Multistrada, or even a used 1199) may be a smarter long-term choice**.
---
### **Recommendation**
1. **If Buying Used:**- **Get a full mechanical inspection** (focus on **engine compression, valve adjustments, cooling system, and electrical components**).
- **Verify thermostat/sensor history** ensure they have been **replaced within the last 2 3 years**.
- **Check for frame cracks** (especially in the **rear subframe area**).
- **Test ride thoroughly** listen for **unusual noises, check for overheating, and verify throttle response**.
2. **If Considering a Restoration/Project Bike:** - **Budget for:**- **Cooling system overhaul** (thermostat, sensors, hoses, radiator).
- **Electrical system upgrades** (new wiring harness, sensors, ECU if needed).
- **Suspension and brake refresh** (forks, shock, calipers, pads).
- **Exhaust and emissions compliance** (if required).
- **Consider a fuel-injected model (998,
Details:
FITS THE 748 916 996 STE ST4S SUPER BIKE. OEM RADIATOR HOSES, thermostat, clamps as shown FROM A 9000 MILES 2002 ST4S.
part #: 55340031a prices
- $67.17-$214.66
specifications cycleswitches:
- for models: St2, St4s, St4
- for makes: Ducati
- mpn: 55340031a
- part type: Switch Thermostat Sensor
offer cycleswitches:
- started: May 24, 2026
- sold: 0
- options: Ship-to-home
- availability: In Stock
- quantity: 1
- best offers: True
general cycleswitches:
- condition: Used
- Electrical Ignition Components > Electrical Ignition Sensors Switches > Ignition Key Switches
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