Audi Q2 Coolant Mystery: Hidden Leak Warning Signs

As someone with some mechanical experience, I dealt with a similar issue on my 2014 Audi Q3 last year. The symptoms were nearly identical, check engine light and decreasing coolant levels without visible leaks. After noticing engine overheating issues, I took it to my workshop where they performed a pressure test on the cooling system. They discovered a faulty connection between the coolant reservoir and one of the main cooling lines. The cable connector had deteriorated over time, causing a slow leak that was hard to spot because the coolant would evaporate quickly due to engine heat. The total repair cost was 95 Euro, which covered the replacement of the connector and labor. It was a relatively straightforward fix once properly diagnosed. However, your situation might be different. To provide more specific guidance, could you share: 1. Are you experiencing any engine overheating? 2. Does the cooling fan seem to be running more than usual? 3. When did you last have your coolant system serviced? 4. Are there any sweet-smelling fumes from the exhaust? These details would help determine if youre dealing with a simple connector issue like mine or potentially something more serious like a water pump or head gasket problem. Consider getting a pressure test done, its usually the most reliable way to locate coolant system leaks.

I had my last service at 192217 KM about 3 weeks ago. After checking more thoroughly, I noticed small drops near the radiator cap area when the engine is hot. When I start the car cold in the morning, there seems to be air pockets forming in the coolant reservoir. The radiator hoses feel firm with no obvious weak spots. I also noticed the water pump area is completely dry, which likely rules out pump failure. Im starting to think its just a faulty radiator cap not holding proper pressure. Has anyone replaced their radiator cap and solved similar symptoms? This would be a much cheaper fix than what I initially feared with the head gasket.

Thanks for the additional details. Your symptoms strongly point to a faulty radiator cap, I had exactly the same issue on my Q3 before the connector problem I mentioned earlier. The air pockets forming in the coolant reservoir are a telltale sign of a failing radiator cap not maintaining proper system pressure. When the cap doesnt seal correctly, it allows coolant to escape as steam when the engine heats up, and air gets pulled in during cooling cycles. A new radiator cap costs around 25 Euro and its an easy DIY fix. Important: ensure you get the correct pressure rating cap (usually stamped on the old one). After replacing mine, I also had to properly bleed the cooling system to remove any remaining air pockets. The process for our engines involves: Fill with correct radiator fluid mixture, Run engine with heat on full, Keep topping up coolant until no more bubbles appear, Let engine complete several heat cycles Watch the coolant level for a few days after replacement. If it stays stable and the air pockets dont return, youve found your issue. If problems persist, then its time to investigate other potential causes like head gasket or cracked cylinder head.

Thanks for the feedback. Just wanted to close this thread with an update: I replaced the radiator cap yesterday and carefully bled the cooling system following your instructions. After 3 heat cycles and about 50km of driving, the coolant level in the reservoir has remained stable with no more air bubbles forming. Total cost was 22 Euro for a genuine cap, way better than my initial fears about head gasket issues! The coolant leak has completely stopped and no more drops near the radiator area. The check engine light also cleared itself after a few driving cycles. One tip for others: when bleeding the cooling system, I found it helpful to gently squeeze the radiator hoses while the engine was warming up. This helped push out stubborn air pockets. Just make sure the engine isnt too hot when doing this. Really glad I checked here before rushing to a workshop. Sometimes the simplest solution is the right one.