Coolant Leak and Overheating - 2018 Q5

This sounds like a classic Audi Q5 water pump failure, a common issue on these models, particularly in the 2018-2020 range.

Causes & Diagnostics:

1. Water Pump Failure: The plastic components of the original water pumps are prone to cracking and leaking over time. This is the most likely culprit.
2. Thermostat Housing: Often integrated or closely located with the water pump, the thermostat housing can also develop leaks.
3. Hose Connections: Less common, but check for loose or cracked coolant hoses.

When to See a Shop: You should take your vehicle to a reputable independent Audi specialist or dealership immediately. Continuing to drive with a significant coolant leak risks severe engine overheating and catastrophic damage.

Repair Steps (What to expect):

• Diagnosis: A shop will pressure test the cooling system to pinpoint the exact source of the leak. They will likely confirm it's the water pump and/or thermostat housing.
• Replacement: The repair typically involves replacing the entire water pump assembly, which often includes the thermostat. It's a fairly involved job, requiring removal of various components to access it.
• Coolant Flush: After replacement, the system will be refilled with the correct G13 (or equivalent) Audi coolant and bled to remove air pockets.
• Potential OBD Codes: P2181 (Performance Malfunction in Cooling System), P0116 (Engine Coolant Temperature Sensor 1 Circuit Range/Performance).

While some DIYers might attempt this, it's generally recommended for professional mechanics due to the complexity and the need for specialized tools to ensure proper sealing and bleeding of the system. Expect the repair to cost several hundred dollars for parts and labor.