Audi SQ7 Coolant Leak Mystifies Owner, Fix Guide

I had a similar issue with my 2018 Audi SQ5, and I have some experience working with cooling systems. The symptoms were identical, check engine light and low coolant warnings without visible leaks. After inspection, it turned out the issue was a faulty electrical connection to the coolant level sensor. The radiator cap and surrounding components were visually fine, but the sensor was giving false readings due to a damaged wire connector. The repair was straightforward once diagnosed. My workshop found that moisture had corroded one of the plug connections, causing intermittent sensor readings. The total repair cost was 95 Euro and took about an hour to complete. They also checked for actual coolant leaks and air pockets in the system but found everything else working properly. Before suggesting specific fixes for your SQ7, could you share: Are you noticing any sweet smells from the engine bay? Does the cooling fan seem to run more frequently than usual? How long has the warning light been appearing? Have you checked the coolant level manually to confirm its actually low? This information would help determine if youre dealing with a similar sensor issue or potentially a different problem in the cooling system.

After 189926 KM, I can confirm the issue was worse than initially suspected. The workshop traced the coolant leak to a hairline crack in the coolant reservoir, which was only visible when the engine was fully warmed up and pressurized. The radiator hoses and connections were inspected but showed no signs of wear. They pressure tested the entire cooling system and found air pockets forming due to the compromised reservoir. The fix required replacing the coolant reservoir and performing a complete system flush. Total repair time was 3 hours, with parts and labor coming to 450 Euro. Worth noting that they also spotted minor seepage around the water pump gasket during inspection, but it wasnt the primary source of the leak. They recommended monitoring it for potential future maintenance. Would strongly suggest getting a pressure test done if you havent already, as some leaks only show up under operating pressure and temperature.

Thanks for the update on your SQ7's coolant issue. On my SQ7, I actually faced a very similar situation at around 180000 KM. The coolant reservoir cracking seems to be a known weak point on these models when they rack up higher mileage. The water pump seepage you mentioned matches my experience too. Initially, my mechanics also spotted minor seepage there, but it progressively worsened over the next few months. I ended up having to replace both the water pump and its gasket about 6 months after the reservoir repair. One tip based on my experience: keep an eye on your coolant temperature gauge and cooling fan behavior. In my case, the fan started running more frequently before the water pump completely failed. The total repair for the water pump replacement came to 780 Euro including parts and labor. Since youve already had the system flushed, just make sure to monitor the coolant level in the reservoir weekly. Any rapid drops could indicate the water pump issue is developing faster than in my case.

After inspecting everything myself, I can now confirm the symptoms others mentioned. The sweet smell is definitely present around the engine bay, and the coolant level in the reservoir drops noticeably every few days. The cooling fan has also started running more frequently than usual. The check engine light first appeared about two weeks ago, and I manually verified the coolant level was indeed low in the coolant reservoir. After topping it up, it dropped again within 48 hours. This matches what others experienced with the hairline crack issue. Based on everyone's input and my symptoms, I'll schedule a pressure test this week. The possibility of both a cracked reservoir and potential water pump issues definitely warrants professional inspection. Better to address it now than risk more severe engine damage. For reference on future costs, I appreciate the detailed breakdown showing 450 Euro for the reservoir repair and potentially another 780 Euro if the water pump needs replacement. Will update the forum once I have the pressure test results and know the full extent of repairs needed.