1987 GMC R1500 Coolant Temperature Sensor: A Guide to Replacement
Solve rough running, poor fuel economy, and stalling in your classic GMC truck by understanding this critical sensor.
- Verify you are replacing the correct two-wire sensor for the computer, not the one-wire sender for the gauge.
- Symptoms of failure include poor MPG, stalling when hot, and black exhaust smoke.
- For a 1987 model, a quality aftermarket sensor is a reliable and cost-effective solution.
- Replacement is a simple DIY task that can be completed in under 30 minutes with basic tools.
Understanding the Two Temperature Sensors
Your 1987 GMC R1500 has two separate parts that measure coolant temperature. It is very important to know which one you need to replace. This guide focuses on the sensor for the engine computer.
- Engine Coolant Temperature (ECT) Sensor: This two-wire sensor talks to the engine's computer (ECM). It affects how your engine runs. It is located on the front of the intake manifold, near the thermostat housing.
- Temperature Gauge Sender: This is a one-wire switch that only controls the temperature gauge on your dashboard. It does not affect engine performance. It is usually found on the driver's side cylinder head, between two spark plugs.
Symptoms of a Failing Coolant Temperature Sensor
A bad ECT sensor often tricks the computer into thinking the engine is always cold. This leads to the computer sending too much fuel. Signs of a bad sensor include:
- Poor Fuel Economy: Your truck will use much more gas than usual because the computer is stuck in the "cold start" mode.
- Stalling When Warm: The engine may start and run fine when cold, but begins to run rough, sputter, or stall as it heats up.
- Black Smoke from Exhaust: A sign of too much fuel being burned, which can exit the tailpipe as black smoke.
- Check Engine Light: Your truck's OBD-I system can trigger a Check Engine Light. The codes for a bad ECT sensor are typically Code 14 or Code 15.
- Hard Hot Starts: The engine may be difficult to restart after it has been run and is fully warm.
Choosing the Right Aftermarket Part
For a classic truck like the 1987 R1500, new original equipment (OEM) parts can be hard to find and expensive. Aftermarket parts are widely available and offer a great balance of quality and price. For a simple electronic sensor like the ECT, a quality aftermarket brand provides reliable performance. Since the sensor is a critical input for the fuel system, choosing a part with good reviews and a warranty is a smart move. For this application, a standard aftermarket sensor is a dependable and cost-effective choice that will restore proper engine function.
Cost of Replacing a Coolant Temperature Sensor
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Sensor | $15 - $40 |
| Shop Labor | $50 - $100 |
| Total Estimated Cost (Shop) | $65 - $140 |
Frequently Asked Questions
Where is the ECT sensor located on a 1987 GMC R1500?
The engine coolant temperature sensor that sends information to the computer is located on the front of the intake manifold, usually right next to the thermostat housing. It has a two-wire electrical connector.
Can I replace the coolant temperature sensor myself?
Yes, this is a very beginner-friendly job. It requires basic hand tools and can typically be done in under 30 minutes. The sensor is easy to access on top of the engine.
What happens if I don't replace a bad sensor?
Driving with a bad ECT sensor will cause persistent poor performance, terrible gas mileage, and potential stalling. Over time, running a constantly rich fuel mixture can damage the catalytic converter and foul spark plugs.
My temperature gauge on the dash is broken. Will this part fix it?
No. The dashboard gauge is operated by a different part called the coolant temperature sender, which is a single-wire unit located on the driver's side cylinder head. This two-wire sensor only communicates with the engine computer.
Technical Specifications
Connector: 2-pin female. Location: Intake manifold, near thermostat housing.
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.
- GMC R1500: