Owner's Problem Description
The owner of a 1998 Chrysler Concorde is attempting to replace the thermostat but is facing difficulties with the alternator removal. After significant effort, including removing hoses and the fan casing, they are concerned about further complications. The engine is overheating despite the temperature gauge not indicating a hot reading. The owner seeks advice on potential next steps and overall vehicle serviceability.
Professional Technical Analysis
The 1998 Chrysler Concorde is equipped with a 2.7L or 3.5L V6 engine, both of which are known for their compact design, making access to components like the thermostat challenging. The reported overheating issue, with symptoms including rapid boiling of coolant within five minutes of driving, suggests a potential failure of the thermostat. The gauge not reading hot may indicate a faulty temperature sensor or gauge itself. Removing the alternator is not typically necessary for thermostat access; rather, only the alternator strut should be detached. The fact that hoses and fan casings were removed indicates an attempt to create space, but this can lead to additional complications such as misalignment or reinstallation difficulties. The current condition of the vehicle highlights the need for a systematic approach to diagnosing the overheating issue after thermostat replacement. The owner should ensure that the cooling system is properly bled and check for any air pockets that might prevent proper coolant circulation.
Possible Causes
Most common causes (ordered by frequency):
- Thermostat Failure: The thermostat may be stuck closed, preventing coolant flow and causing the engine to overheat. This would explain the rapid boiling of coolant. Typical failure occurs in thermostats after 100,000 miles, especially in vehicles that have experienced cooling system issues. The replacement thermostat should ensure proper opening temperature, typically around 195°F for this engine. - Coolant boiling, engine temperature rising rapidly, previous cooling system issues.
- Faulty Temperature Sensor: If the temperature sensor is malfunctioning, it may not accurately reflect the engine's temperature, leading to a false reading on the gauge. This could result in the owner believing the engine is not overheating while it is actually overheating. Testing the sensor with a multimeter should reveal proper resistance values at various temperatures. - Gauge not indicating hot, potential DTCs related to coolant temperature, inconsistent engine temperature readings.
- Air Pockets in Cooling System: After any service involving the cooling system, air pockets can form, preventing proper coolant circulation. This could lead to localized overheating, especially if the thermostat is replaced without thoroughly bleeding the system. It is critical to follow the manufacturer's bleeding procedure to ensure all air is removed. - Overheating symptoms after service, difficulty bleeding the system, inconsistent coolant flow.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Identify Engine Type: Confirm whether the engine is the 2.7L or 3.5L V6. The thermostat location differs, affecting the repair approach. The 2.7L has the thermostat located near the lower radiator hose, while the 3.5L is more accessible at the top. Confirm by checking the vehicle identification number (VIN) or engine label.
- STEP 2 - Assess Cooling System: Inspect the entire cooling system for leaks, ensuring that hoses and connections are secure. Check the coolant level and condition, and look for any signs of air pockets in the system. Use the GeekOBD APP to scan for any related trouble codes that may indicate sensor issues or overheating concerns.
- STEP 3 - Test Temperature Sensor: Remove and test the temperature sensor using a multimeter to check for proper resistance values. The sensor should read approximately 2,200 ohms at room temperature and decrease as the temperature rises. If it fails to provide accurate readings, replacement may be necessary.
- STEP 4 - Thermostat Replacement and System Bleeding: Once the thermostat is accessible, replace it with a new unit that meets OEM specifications. After installation, thoroughly bleed the cooling system to eliminate any air pockets, following the manufacturer's recommended procedure. Monitor the system using the GeekOBD APP to ensure proper operation post-repair.
