1. Air in the Cooling System: This is the most likely culprit. When you replaced the hose, you probably introduced air into the cooling system. Air pockets can disrupt coolant flow, leading to overheating and erratic engine operation. The engine might be cutting out due to overheating or because the air is interfering with the thermostat's operation.
* Solution: Bleed the cooling system properly. This involves carefully refilling the radiator and allowing the engine to run until all the air bubbles are purged. Consult your vehicle's repair manual for the specific procedure, as it can vary. Often, it involves opening a bleed valve on the engine block or radiator until coolant flows freely without bubbles.
2. Loose or Damaged Hose Clamps: If the new hose isn't clamped securely, it could cause a leak, leading to similar problems.
* Solution: Check all hose clamps. Ensure they're tightened properly and the hose is seated correctly.
3. Thermostat Issues: The air in the system might be affecting the thermostat's function. A faulty thermostat can also cause similar problems.
* Solution: Check the thermostat. If it's stuck closed or open, replace it.
4. Damaged or Disconnected Vacuum Lines or Sensors: It's possible you accidentally bumped or disconnected something near the radiator or upper hose during the replacement. The engine's computer relies on various sensors and vacuum lines for proper operation.
* Solution: Carefully inspect all vacuum lines and sensors near the area where you worked. Ensure everything is properly connected and undamaged.
5. Incorrect Hose: While unlikely, you might have installed the wrong hose.
* Solution: Double-check that you have the correct part number.
6. Other Underlying Issues (Less Likely): The rough idle and stalling *could* indicate unrelated problems like:
* Ignition System Problems: Worn spark plugs, wires, or a failing distributor (if equipped) can cause rough running and stalling.
* Fuel System Issues: A clogged fuel filter, bad fuel pump, or issues with the fuel injectors can cause fuel delivery problems.
* Mass Airflow Sensor (MAF) or Throttle Position Sensor (TPS) Problems: These sensors can cause erratic engine performance if malfunctioning.
Troubleshooting Steps:
1. Bleed the Cooling System: This is the first and most important step.
2. Inspect Hose Clamps: Ensure they're tight and the hose is secure.
3. Check for Leaks: Visually inspect the entire cooling system for any leaks.
4. Check Vacuum Lines and Sensors: Look for any disconnected or damaged components.
5. If problems persist, consult a repair manual: It will provide detailed instructions on bleeding the cooling system and other troubleshooting steps. You may need to use a scan tool to check for diagnostic trouble codes (DTCs).
If you've completed all of these steps and the problem persists, you'll likely need to take your vehicle to a mechanic for diagnosis. It's always best to be thorough and eliminate the simple things first before assuming more complex issues.
