The coolant temperature sensor plays a vital role in your Freightliner DD15 engine’s cooling system. A faulty sensor can lead to inaccurate temperature readings, causing overheating and potential engine damage. This article will guide you through a real-world experience of diagnosing and replacing a faulty Dd15 Coolant Temp Sensor.
Identifying a Faulty DD15 Coolant Temp Sensor
The problem started with the engine fan constantly running and the temperature gauge spiking to 200 degrees immediately upon starting, even after sitting overnight. This pointed towards a potential sensor issue. While the Freightliner DD15 uses similar-looking sensors for various functions, including the coolant temperature, pinpointing the correct one can be tricky. One common misconception is that the sensor located near the thermostat housing is the culprit. However, in this case, replacing that sensor didn’t solve the problem. There were no error codes displayed either.
Locating the DD15 Coolant Temp Sensor
The key to resolving the issue was identifying the correct sensor. After some trial and error, the faulty sensor was found near the top radiator hose connection to the cylinder head, just below the EGR cooler and facing the fan. Disconnecting this sensor’s pigtail immediately caused the temperature gauge to drop, confirming it was the source of the problem. Driving to the repair shop with the sensor disconnected triggered a check engine light, but prevented further overheating and engine shutdown.
Replacing the DD15 Coolant Temp Sensor
Replacing the sensor requires a few key considerations. First, having rubber stoppers or foam ear plugs handy can minimize coolant loss during the swap. Second, remember the copper crush washer, which is often overlooked. Reusing the old one is possible but getting a new one is recommended. Finally, removing the sensor’s electrical connector can be challenging due to brittle plastic. Using a small pick tool to carefully release the connector’s clip is recommended. If the connector breaks, wrapping electrical tape around the sensor’s connector head can provide a secure temporary fix.
Conclusion
A faulty DD15 coolant temp sensor can lead to significant overheating problems. This firsthand experience highlights the importance of correctly identifying the sensor responsible for providing temperature readings to the gauge and ECM. While visually similar sensors exist in the DD15 engine, the one located near the top radiator hose connection is the critical component for accurate temperature monitoring. Remember to use the tips mentioned above for a smoother replacement process. Although replacing the thermostat in this instance was unnecessary, it served as a preventative measure.
