Diagnosing a Coolant Leak in an Audi A6 C7 (2011-2018)

Tools Required

• Flashlight
• Coolant pressure tester
• UV dye and UV light (optional)
• Mirror on a telescopic stick
• Basic hand tools (screwdrivers, pliers, socket set)
• Safety gear (gloves, safety glasses)

Step 1: Visual Inspection

1. Park Safely: Ensure the vehicle is parked on a level surface and the engine is cool before starting the inspection.
2. Check Coolant Level: Open the hood and inspect the coolant reservoir for proper coolant level.
3. Inspect for Puddles: Look under the car for any signs of coolant puddles.
4. Examine Engine Bay: Use a flashlight to check around the engine bay for any signs of coolant residue or leaks. Pay special attention to:
   • Radiator and hoses
   • Coolant reservoir
   • Water pump area
   • Heater core connections
   • Thermostat housing

Step 2: Pressure Test

1. Pressure Tester Setup: Attach the coolant pressure tester to the radiator or coolant reservoir cap fitting.
2. Pressurize System: Pump the tester to the recommended pressure (usually around 15 psi; check the vehicle's service manual for exact specifications).
3. Inspect for Leaks: With the system pressurized, inspect all components for signs of leakage. Use a mirror to check hard-to-see areas.
4. Release Pressure: Carefully release the pressure after testing.

Step 3: UV Dye Test (If Needed)

1. Add UV Dye: Pour the specified amount of UV dye into the coolant system. Check the dye's compatibility with your vehicle’s coolant.
2. Run Engine: Start the engine and let it run for about 15 minutes to circulate the dye.
3. Inspect with UV Light: Use a UV light to check for fluorescent indications of leaks.

Common Leak Locations and Repair Instructions

1. Radiator and Hoses

• Diagnosis: Look for cracks or wetness on the radiator and hoses.
• Repair: Replace any damaged hoses. If the radiator is leaking, it may need to be replaced or repaired by a specialist.

2. Water Pump

• Diagnosis: Check for leaks around the water pump. Look for coolant traces around the pump housing or weep hole.
• Repair: Replace the water pump if a leak is found.

3. Coolant Reservoir

• Diagnosis: Inspect for cracks or leaks around the seams.
• Repair: Replace the coolant reservoir if damaged.

4. Thermostat Housing

• Diagnosis: Check for leaks around the thermostat housing.
• Repair: Replace the gasket or the entire thermostat housing if needed.

5. Heater Core

• Diagnosis: Look for coolant leaks inside the cabin or wet carpets.
• Repair: Replacing the heater core can be complex, often requiring dashboard removal. Consult a repair manual for specific instructions.

Conclusion

If you identify a specific component leaking, proceed with replacing or repairing it as necessary. If the leak persists or is difficult to locate, consider consulting a professional technician for further diagnosis. Always ensure the cooling system is properly refilled and bled of air after repairs to prevent overheating.