According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 2015 Lincoln Navigator has 4 documented known issues, with 3 rated critical. The most serious are Navigator Rear Air Suspension Bag/Compressor Failure ($700-$2,400 repair), Navigator 3.5L EcoBoost Timing Chain Stretch ($1,800-$6,000 repair) and Air Ride Suspension Compressor Burnout from Air Bag Leaks ($400-$2,200 repair). Across all issues with published estimates, repair costs range from $250 to $6,000. DIY maintenance guides at au7o.io.