Audi Q7 Mysterious Coolant Loss Needs Expert Diagnosis

Had a similar issue with my 2014 Audi Q5 3.0T. The frequent coolant level drops without visible leaks pointed to an internal issue. After inspection, the problem was traced to microscopic cracks in the water pump housing, causing coolant to seep slowly and evaporate before creating visible puddles. The coolant reservoir would show low levels every few weeks, and the check engine light kept coming on due to the system detecting air pockets in the cooling system. This required a thorough diagnostic because the leak was not immediately apparent. The root cause turned out to be more complex than initially thought. Beyond the water pump issue, there was also a failing head gasket allowing small amounts of coolant to escape. These symptoms are fairly common in these engines when they reach higher mileage. This was definitely a serious repair requiring: Complete cooling system pressure test, Water pump replacement, Head gasket replacement, System flush to remove air pockets, New coolant and proper bleeding of the system Recommend getting a proper pressure test done first to identify the exact location of any leaks before proceeding with repairs.

Thanks for sharing your experience. I had the same invisible coolant leak issue with my Audi Q7 and got it fixed about 6 months ago. The mechanic found hairline cracks in the water pump housing and some worn radiator hoses that needed replacement. The coolant reservoir would show low levels but there were never any puddles under the car. Can you remember roughly how much you paid for the repairs in your case? Just curious if the costs were similar. Also, has everything been running smoothly since the fix, or have you noticed any other cooling system problems?

Thanks for asking about the repair costs. In my case, the initial diagnosis pointed to a faulty cable connection affecting the cooling system sensors, which was creating false low coolant warnings. The fix was relatively simple and cost 95 Euro for the electrical repair. Since having the mechanic address this issue, the coolant level has remained stable and the warning lights have stayed off. The cooling fan operates normally now, and I have not experienced any further problems with the coolant reservoir levels. This turned out to be much less severe than the water pump and head gasket issues I initially feared. Regular monitoring shows the coolant level is holding steady, and there have been no leaks from the radiator hoses or other components. If your repairs included a water pump replacement and new hoses, your costs were likely higher than mine since my issue was purely electrical. The cooling system has been running perfectly for the past 6 months since the fix.

Following a thorough inspection at my new mechanic, they found the issue was actually more complex than the previous shop suggested. The water pump housing had developed hairline cracks and several radiator hoses were deteriorating. The complete repair included replacing the water pump assembly, all connecting hoses, and a full system flush to remove air pockets from the cooling system. The total repair came to 1200 Euro, including parts and labor. While it was a significant expense, the cooling fan now operates properly and the check engine light has stayed off. The coolant reservoir maintains its proper level, and I haven't had to add any radiator fluid since the repair. Really glad I switched mechanics, the new shop did a thorough diagnostic instead of just topping off the coolant like my previous mechanic kept doing. Six months later, the cooling system is working perfectly with no more mysterious leaks or warning lights.