What size thread is a GM temp sensor?

GM temperature sensors come in a few common thread sizes, with the two most widespread being 1/4-18 NPT and M12x1.5. The exact size depends on the specific engine family, sensor type, and model year, so always verify against the vehicle or part number before purchasing or installing a replacement.

Common thread sizes you’re likely to encounter

These are the thread sizes GM most often uses for coolant temperature sensors and related temperature-sensing ports. The actual size for your car depends on the engine family and year.

• 1/4-18 NPT — the workhorse size for many GM coolant temperature sensors on a wide range of older models and mainstream replacements.


• M12x1.5 — increasingly common on newer GM engines and some sensor assemblies located in water necks or intake regions.


• 1/8-27 NPT — appears occasionally on certain specialty or older models; verify with the exact part and vehicle.


• Other sizes — rare in typical GM street vehicles, but some applications may use alternative NPT or metric threads; always confirm with the service manual or part number.

In practice, the two sizes you’re most likely to need to deal with are 1/4-18 NPT and M12x1.5. When in doubt, check the vehicle’s service manual or pull the exact OEM sensor part number to match the correct thread.

How to identify the correct size

To determine the precise thread size for your GM temp sensor, follow these steps so you don’t guess and risk cross-threading or leaks.

1. Consult the vehicle’s service manual or GM parts catalog for the exact sensor specification by year, make, and model.


2. Compare the existing sensor port with standard thread gauges or measure the diameter and pitch of the threads you remove.


3. Remove the old sensor and note any markings on the body that indicate thread size or part number; use that information to order a correct replacement.


4. If you’re unsure, bring the old sensor to an auto parts store or use the VIN to pull the OEM replacement, which ensures the correct thread.


5. When installing, use the recommended torque and avoid over-tightening; use appropriate sealant or an O-ring if the port requires it, and never force a sensor into a mismatched thread.

By verifying the size ahead of installation, you ensure a proper seal, correct electrical fit, and reliable temperature readings for your GM engine.

Engine family snapshots: typical patterns by GM line

GM LS family and newer engines

Many modern GM engines in the LS family use a coolant temperature sensor with an M12x1.5 thread in the water neck or thermostat housing area; this is common across many 1999–present models.

Older GM small-blocks and traditional platforms

Historically, a 1/4-18 NPT thread has been standard for coolant temperature sensors mounted in the thermostat housing or water outlet on a wide range of older GM engines.

Specialty or niche GM applications

Some niche applications or regional models may feature nonstandard ports or alternate threads; in those cases, checking the exact part number and the service data is essential.

Bottom line and practical guidance

The majority of GM temperature sensors you’ll encounter fall into two main sizes: 1/4-18 NPT and M12x1.5. Confirm the exact size using the vehicle’s manual, the sensor’s part number, or by precisely comparing the port and old sensor. When in doubt, sourcing the OEM replacement for your specific year/model is the safest path to a correct fit.

Summary

GM uses multiple thread sizes for temperature sensors, with 1/4-18 NPT and M12x1.5 being the most common. Always verify against the vehicle’s service information or the actual sensor you’re replacing to ensure a proper fit and seal. Proper identification helps prevent leaks and ensures accurate temperature readings across GM’s diverse lineup.

What size thread is a LS engine temp sensor?

The standard thread size for an LS engine coolant temperature sensor is M12-1.5, which is a metric thread. However, many aftermarket sensors use a different thread, most commonly 1/8-inch NPT. Adapters are available to bridge this gap, converting the M12-1.5 port to a 1/8-inch NPT thread, making it easier to use a wider variety of sensors with an LS engine. 
LS temperature sensor thread sizes

• Original/Factory: M12-1.5 (metric)
• Aftermarket: Often 1/8-inch NPT (National Pipe Thread) 

How to use different sensors

• For factory sensors: You can directly screw them into the LS cylinder head because they have the correct M12-1.5 thread size. 
• For aftermarket sensors: If your aftermarket sensor is 1/8-inch NPT, you will need an adapter that screws into the M12-1.5 port on the engine block and provides a 1/8-inch NPT female thread for your sensor. 

Why adapters are common

• Engine swaps: When putting an LS engine into a vehicle with a different cooling system, adapters allow you to seamlessly integrate older or aftermarket sensors that use a standard 1/8-inch NPT thread.
• Sensor variety: The adapter gives you a much larger selection of available temperature sensors to choose from for your gauge or computer system. 

What size thread is a GM intake air temperature sensor?

GM intake air temperature (IAT) sensors typically use one of two thread sizes: 3/8"-18 NPTF or M14 x 1.5mm metric. The 3/8" NPTF thread is common on many aftermarket sensors designed for custom applications, while the M14 x 1.5mm thread is often found on Delco and Delphi sensors for factory installations. 
Thread sizes for GM IAT sensors

• 3/8"-18 NPTF: This is a common thread size for standalone or universal GM IAT sensors. It's a tapered pipe thread and is often used when a sensor bung is welded into an intake pipe. 
• M14 x 1.5mm: This is a metric thread size that is frequently used on factory-style GM sensors, particularly from brands like Delco and Delphi. 

How to choose the right sensor

• For aftermarket/custom setups: If you are welding a bung into a custom intake tube, you will likely need a sensor with a 3/8" NPTF thread. 
• For direct replacement: If you are replacing a sensor in a factory application, verify the original thread size. It is likely the M14 x 1.5mm thread, especially on newer vehicles, though it is always best to confirm the exact thread on your sensor before purchasing a new one. Some sensors may also have different plug styles that need to be matched. 

What size thread is a GM oxygen sensor?

The most common GM oxygen sensor thread size is M18 x 1.5mm. However, some newer vehicles and some motorcycles may use a smaller M12 x 1.25mm thread. Always confirm the specific size for your vehicle, but be prepared for the M18 x 1.5mm as the standard for many applications. 
Common GM oxygen sensor thread sizes 

• M18 x 1.5mm: This is the most common size found on many GM passenger vehicles and older motorcycles. 
• M12 x 1.25mm: This size is used on some newer vehicles and motorcycles. 

Tips for installation and repair

• Check for damage: If you encounter damaged threads, do not force a new sensor in. Instead, use a thread chaser tool to clean or repair the existing threads. 
• Use anti-seize: Applying anti-seize compound to the threads of the new sensor can help prevent future corrosion and make future removal easier. 
• Use the right tool: A thread chaser is preferred over a tap to repair the threads, as it restores the original thread form without removing extra material. 
• Verify socket size: While the thread is metric, the socket to remove the sensor is often 7/8-inch (22mm). 

What is the thread pitch of a GM temp sensor?

GM Intake Air Temp Sensor Thread Pitch 3/8" NPT for Misc Tuning/Turbo GM 2 Wire. Weight: 0.25 Lbs / 0.11 Kg. IAT (Intake Air Temp) sensor GM for misc tuning/turbo use.