NPTF Coolant Water Temperature Sensor 19mm 25036979 15326386 6238236

Water Temperature Sensor 25036979/15326386/1338450/6238236/TS1007512B1/01R43039R01

As an NTC (Negative Temperature Coefficient) thermistor-type sensor, the 25036979 exhibits the following resistance behavior:

• Low coolant temperature → High resistance → High voltage signal to ECU

• High coolant temperature → Low resistance → Low voltage signal to ECU

The ECU interprets these voltage variations to determine engine operating temperature and makes corresponding adjustments to fuel delivery, ignition timing, and radiator fan operation.

The Water Temperature Sensor (Part No. 25036979) is an OE-grade component recognized across multiple manufacturer platforms. This part number corresponds to the following reference information:

This sensor meets automotive industry safety and performance standards, guaranteeing reliability equivalent to original equipment. It is backed by rigorous testing for longevity and precision.

The 25036979 water temperature sensor is designed for compatibility with a vast range of vehicle applications across multiple manufacturers, spanning several decades of production.

Important: Always verify thread size (3/8" x 18 NPTF), connector type (2-pin, oval), and vehicle compatibility with your specific application before purchase.

A failing or faulty water temperature sensor can manifest through various drivability and performance issues. Early recognition of these symptoms can prevent more serious engine damage and costly repairs.

One of the most common indicators of a faulty sensor is the illumination of the Check Engine Light on the dashboard. The ECU detects abnormal resistance values or signal patterns from the sensor and stores corresponding Diagnostic Trouble Codes (DTCs).

A faulty sensor may provide incorrect temperature data, resulting in erratic or inaccurate readings on the vehicle's temperature gauge. The gauge may show the engine running cooler or hotter than it actually is, or the needle may fluctuate unpredictably.

If the sensor fails to detect rising coolant temperatures accurately, the ECU may not activate the cooling fan at the appropriate time. This can lead to engine overheating — one of the most serious consequences of sensor failure.

Incorrect temperature readings can impair the ECU's ability to enrich the air-fuel mixture during cold starts. This may result in difficulty starting the engine when cold, extended cranking times, or engine stalling shortly after starting.

When the sensor provides inaccurate temperature data, the ECU may incorrectly adjust fuel delivery, often resulting in a richer-than-necessary air-fuel mixture. This condition leads to noticeably reduced fuel economy.

Inaccurate temperature data can disrupt the ECU's calculations for ignition timing and fuel delivery, resulting in reduced engine power, rough idling, or hesitation and surging during acceleration.

A faulty sensor can cause the ECU to maintain an elevated idle speed as part of its default or "limp-home" strategy. The engine may idle at higher RPMs than normal, even after reaching operating temperature.

A faulty sensor can cause elevated exhaust emissions and interference with the lambda (oxygen sensor) control loop, potentially causing the vehicle to fail emissions testing.

A faulty sensor may cause the radiator cooling fan to run continuously or fail to turn on when the engine reaches operating temperature.

Visual inspection may reveal:

• Cracks in the sensor housing

• Coolant leaks around the sensor mounting area

• Corrosion on electrical connectors

• Damaged or frayed wiring

When purchasing a replacement water temperature sensor (Part No. 25036979), the following factors should be carefully evaluated to ensure proper fitment, reliable performance, and long service life.

Before purchasing, confirm that the sensor's thread size (3/8" x 18 NPTF) matches your vehicle's cylinder head or engine block mounting point. This is a National Pipe Thread (NPT) fitting — ensure your engine's mounting boss is compatible with NPT threads. A thread mismatch is one of the most common installation issues encountered during replacement.

This sensor features a 2-pin oval connector. Verify that the electrical connector type matches your vehicle's wiring harness. Connector mismatch is another common issue — if the connector does not match, the sensor cannot be installed without modification to the wiring harness.

While the 25036979 sensor is compatible with an exceptionally wide range of vehicles — including Chevrolet, Buick, Cadillac, GMC, Oldsmobile, Pontiac, Opel, Vauxhall, Daewoo, Isuzu, and Honda models — always cross-reference with your vehicle's specific year, make, model, and engine displacement. The sensor spans multiple decades of production, from the early 1980s through the 2010s.

Opt for sensors manufactured with corrosion-resistant brass housings and high-temperature plastic terminal housings. High-quality sensors feature:

• Brass terminals for excellent conductivity

• Sealing O-rings as specified by OE

• Testing below freezing and above boiling to match OE resistance characteristics

• Enhanced resistance to thermal degradation

• Superior protection against coolant corrosion

• Longer operational lifespan

The part number 25036979 is an Original Equipment number associated with General Motors and multiple other manufacturers. When purchasing, ensure the sensor displays the correct OE number and associated reference numbers to guarantee proper specification.

When replacing a faulty water temperature sensor, it is advisable to inspect related cooling system components:

• Upper and lower coolant hoses for cracks, leaks, or deterioration

• Radiator for cracks, leaks, or damage

• Radiator cap for proper sealing

• Coolant level and condition

• Cooling fan operation

Always refer to the vehicle owner's manual for the correct coolant type and replacement procedure.

Before installing the new sensor:

• Inspect the wiring harness connector for corrosion, damage, or loose pins

• Check for broken or frayed wires

• Clean connector terminals if necessary

• Ensure a secure, weather-tight connection upon installation

While the symptoms listed above can indicate a faulty water temperature sensor, many of these symptoms can also be caused by other issues such as:

• Faulty coolant thermostat

• Wiring harness problems

• ECU issues

• Cooling system leaks

• Cooling fan motor failure

It is recommended to have the vehicle properly diagnosed using a scan tool to read stored DTCs before replacing the sensor. This ensures that the sensor is indeed the root cause of the symptoms and prevents unnecessary parts replacement.

• Allow the engine to cool completely before attempting sensor removal or installation to prevent burns from hot coolant

• The sensor features a 3/8" NPT thread — use a 19 mm spanner for installation and removal

• Apply a small amount of thread sealant (compatible with coolant systems and NPT fittings) to the sensor threads to prevent leaks

• Tighten the sensor to the manufacturer's specified torque value (avoid over-tightening, which can damage the sensor or the mounting point)

• After installation, check coolant level and top up if necessary

• Start the engine and check for leaks around the sensor mounting area

• Verify that the temperature gauge operates correctly and the Check Engine Light (if illuminated) has been cleared

If the sensor is not installed immediately, store it in a cool, dry environment away from direct sunlight and moisture. Avoid dropping or subjecting the sensor to mechanical shock, as this can damage the internal sensing element.

When purchasing from a supplier, review the warranty coverage and return policy. Quality sensors should be backed by appropriate warranty protection against manufacturing defects — typically 12 months. Keep the original packaging and proof of purchase for warranty claims if needed.

The water temperature sensor contains an NTC (Negative Temperature Coefficient) thermistor sensing element that exhibits a predictable decrease in electrical resistance as temperature increases. Installed in the engine coolant circuit, the sensor makes direct contact with the engine coolant to accurately measure temperature. The sensing element ensures proper fuel mixture and ignition timing under all climatic conditions.

The ECU supplies a reference voltage to the sensor. As the sensor resistance changes with temperature, the voltage signal varies proportionally:

• Low coolant temperature → High resistance → High voltage signal to ECU

• High coolant temperature → Low resistance → Low voltage signal to ECU

The ECU converts this voltage signal into a temperature reading and uses it for critical engine management calculations, including fuel delivery, ignition timing, and cooling fan operation.

The coolant temperature sensor plays a vital role in:

• Regulating fuel injection for optimal air-fuel mixture

• Controlling ignition timing for maximum efficiency

• Activating radiator fan operation to prevent overheating

• Ensuring proper engine performance and fuel economy

• Reducing harmful emissions

Common failure modes include:

• Condensation damage – Moisture ingress can cause internal corrosion

• Electrical connection failure – Corroded or loose connector pins

• Internal thermistor failure – Open or short circuit conditions

• Physical damage – Cracks from thermal stress or mechanical impact