SQ5 Coolant Loss Mystery, Causes & Owner Experiences

Had a similar issue on my 2017 Audi S4 last season. The symptoms matched exactly, low coolant warnings and check engine light coming on intermittently. Initially suspected a simple leak, but inspection revealed the water pump was failing. The plastic impeller inside had started deteriorating, causing inadequate coolant circulation. This is actually a common failure point on these engines. The coolant reservoir showed correct levels at first, but the system was developing air pockets due to the faulty pump. Once replaced, the technician had to properly bleed the cooling system to remove all trapped air. Important steps we took: Pressure tested the entire cooling system, Inspected the head gasket for potential failure, Checked if the cooling fan was operating correctly, Verified all hose connections were secure This turned out to be quite serious as continued operation could have led to engine overheating. The repair involved removing several components to access the water pump. If your symptoms match, recommend getting it checked soon rather than waiting for complete failure.

Thanks for the detailed breakdown of your water pump issue. Your case sounds really similar to what happened to me. My radiator hoses were actually fine and the radiator cap was sealing properly, but the mechanic also found a failing water pump on my SQ5. Did you happen to remember the total repair cost? And has everything been running smoothly since the fix? I want to make sure I budget correctly and get a sense of whether any other cooling system components might need attention soon.

Actually turned out much simpler in my case. After taking it back to the mechanic, they found the cooling fan wasnt activating due to a faulty electrical connection. The coolant level was too low because of this, but there was no actual leak in the system. The fix only required repairing a damaged cable and plug connection to the cooling fan assembly. Total cost was 95 Euro for parts and labor. Much better than facing a complete water pump replacement. The car has been running perfectly for the past 6 months with no coolant issues or warning lights. They did a full check of the radiator hoses and water pump while it was in, and everything else in the cooling system was working as it should. Worth noting that electrical issues can sometimes mimic more serious problems. Getting a proper diagnosis saved me from unnecessarily replacing major components.

Finally got my car back from the shop yesterday. Like others mentioned, it was indeed the water pump causing all the trouble. The mechanic found small cracks in the housing that were letting coolant seep out slowly. They also spotted some wear on the impeller, which explained the poor coolant circulation. Total repair came to 650 Euro including parts and labor. They had to remove quite a few components to access the water pump, but at least they caught it before any engine overheating damage occurred. The coolant reservoir is now maintaining proper levels and the check engine light has stayed off. They also did a complete pressure test of the cooling system afterward to make sure there were no other leaks. Everything else checked out fine, head gasket was good, cooling fan working properly, and all hoses tight. Been driving it for a few days now and temperature gauge stays exactly where it should. Definitely feeling better having this fixed before it turned into a bigger problem.