BMW 528i (1979-1987) Coolant Temperature Sensor: A Comprehensive Guide
Is your classic 528i running rough, getting poor gas mileage, or showing an erratic temp gauge? The coolant temperature sensor could be the culprit.
- Your 528i likely has two separate coolant sensors; one for the engine computer (DME) and one for the gauge. Identify the correct one before buying.
- A bad DME sensor can cause poor fuel economy, black smoke, and hard starting.
- Replacement is a simple DIY job that can be done in under 30 minutes with basic tools.
- For this part, a quality aftermarket brand is a reliable and budget-friendly alternative to OEM.
Understanding the Coolant Temp Sensor in Your E12 or E28 528i
Your 1979-1987 BMW 528i, which includes both the E12 (1979-1981) and E28 (1982-1987) chassis, relies on precise temperature readings to run properly. A failing Engine Coolant Temperature (ECT) sensor can cause a wide range of problems, from poor fuel economy to a no-start condition. It's a common failure point on older vehicles due to years of heat cycles and vibration.
Two Sensors, Two Jobs
It is critical to know that these classic BMWs typically have two separate coolant temperature sensors. One sensor sends information to the engine computer (DME) to control engine performance. The other sensor sends information to the temperature gauge on your instrument cluster. The DME sensor is usually a two-prong sensor (often with a blue, white, or violet top), while the gauge sender is often a single-prong unit. Make sure you are ordering the correct sensor for the problem you are experiencing.
Common Symptoms of a Bad Coolant Temperature Sensor
A bad DME sensor tells the computer the wrong temperature, leading to poor engine performance. A bad gauge sender will simply give you an incorrect reading on the dash. Here are the most common symptoms:
- Poor Fuel Economy: If the sensor is stuck on a "cold" reading, the computer will continuously send too much fuel to the engine, drastically reducing your MPG.
- Black Smoke from Exhaust: This is a direct result of the engine running too rich (too much fuel), and the unburnt fuel exits through the exhaust.
- Hard Starting (Especially when warm): If the sensor is telling a warm engine that it's cold, the resulting rich fuel mixture can flood the engine, making it difficult to start.
- Erratic or Non-Functioning Temperature Gauge: If the gauge sender fails, the needle on your dash may not move, or it may jump around randomly.
- Engine Overheating: In some systems, the ECT sensor helps control the electric cooling fan. A failed sensor might not trigger the fan, leading to overheating in traffic.
Choosing the Right Aftermarket Part
For a classic vehicle like the E12 or E28 528i, the original parts were often made by Bosch. While OEM is always an option, high-quality aftermarket brands provide a reliable and cost-effective alternative for a simple component like a temperature sensor. Brands like URO, FAE, and Febi are common in the aftermarket and offer a dependable solution. Given the low cost of the part, there is little reason to consider a used sensor.
Before you buy, it's a good idea to look at the sensor you plan to replace. Note the color of the plastic connector and count the number of electrical pins to ensure you order the correct part for your specific year and model.
| Part Type | Typical Cost |
|---|---|
| New Aftermarket (Replacement) | $17.82 |
| New OEM (Bosch) | $25 - $50 |
| Shop Labor | $75 - $150 |
Frequently Asked Questions (FAQ)
Where is the coolant temperature sensor located on my 1979-1987 528i?
The coolant temperature sensors are typically located on the thermostat housing or on the cylinder head, near the front of the engine. You will likely see two sensors in this area; one for the computer and one for the gauge.
Can I replace the coolant temperature sensor myself?
Yes, this is a very DIY-friendly job for most home mechanics. The sensor is usually easy to access. The job involves unplugging the electrical connector, unscrewing the old sensor, and quickly screwing in the new one to minimize coolant loss. The entire process often takes less than 30 minutes. Always work on a cold engine to avoid burns.
Should I replace the sealing washer?
Yes, absolutely. Always use a new sealing washer or O-ring with the new sensor. Re-using the old one is a common cause of coolant leaks after the repair. Most new sensors will come with the required seal.
Are there any recalls for the coolant temperature sensor on my 528i?
No, there are no specific recalls or technical service bulletins (TSBs) from the NHTSA related to the engine coolant temperature sensor for the 1979-1987 BMW 528i. Any failure is typically due to the age and wear of the component.
Technical Specifications
OEM Part Numbers: 12631279716 12631279719 13621357414 62110788115
Typically features a 19mm hex size and M12x1.5 or M14x1.5 thread. Can be a 1-pin (gauge) or 2-pin (DME) connector.
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.