VW Phaeton Trans Failure: Cooling System Connection

I had a similar issue with my 2007 VW Passat, and since I have some experience working on VAG cars, I understand your concern with the transmission symptoms. When my transmission started acting up with similar symptoms, I initially thought it was a major transmission failure. The check engine light and grinding noises had me worried about expensive repairs. After using a pressure gauge to test the transmission cooling system, the workshop discovered the issue was actually a faulty wiring connector at the transmission control module. The repair involved: Testing the radiator coolant circulation, Checking transmission fluid levels, Replacing damaged wiring and connector, Clearing transmission control module codes Total cost was 95€ for the repair including parts and labor. Car overheating was prevented by catching this early, which could have led to more serious transmission damage. To help diagnose your specific case, could you share: Current transmission fluid level and condition, When exactly the symptoms started, Whether you notice any leak detection dye traces around transmission components, If symptoms change when engine is cold vs warm The Phaeton has a more complex cooling setup than my Passat, so these details would help provide more targeted advice for your situation.

Just had my 34076km service and they found the root cause. The transmission oil cooler was damaged, allowing coolant to mix with transmission fluid. This explained the slipping and grinding. After replacing the oil cooler and flushing both cooling system and transmission, all warning lights cleared and shifting returned to normal. The leak detection test confirmed no more cross-contamination between systems. The cooling fan and radiator temperature readings are now stable. Important to catch these issues early before more severe transmission damage occurs. Cost breakdown: 850€ parts 450€ labor

Glad you got it sorted out. Your experience matches what I discovered with my transmission issues, the oil cooler is a critical component that often gets overlooked. When mine failed, I also had coolant mixing with transmission fluid, causing similar symptoms. The price you paid is reasonable considering the work involved. My repair actually cost slightly more at 1400€ total because the pressure sensor also needed replacement along with the oil cooler. The cooling system flush is crucial, my mechanic found metal particles that could have caused more damage if left unchecked. A tip for others reading: regular pressure gauge testing of the cooling system can help catch these problems before they cause major transmission damage. The radiator repair itself is straightforward, but diagnosing cross-contamination early saves thousands in potential transmission replacement costs. Monthly checks of transmission fluid color and coolant levels can provide early warning signs. If the fluid looks milky or has particles, get it checked immediately. The cooling system integrity directly impacts transmission longevity.

Thanks for sharing the solution! After dealing with several shops and stress over potential major transmission repairs, finding the exact issue was a relief. The oil cooler replacement fixed all symptoms and saved me from a complete transmission rebuild. The total cost of 1300€ was high but worth preventing further damage. Monthly fluid checks are now part of my maintenance routine to catch any future radiator repair needs early. A pressure gauge test during service intervals seems like cheap insurance against transmission problems. This experience taught me that transmission warning signs need immediate attention, but they dont always mean complete failure. The link between cooling system health and transmission performance is critical. Having a proper leak detection process helped identify the real problem without replacing unnecessary parts. My transmission now shifts perfectly and all warning lights remain off. Hope this helps others with similar symptoms focus their diagnostic process on the cooling system first.