Two problems related to gas recirculation valve (egr valve) have been reported for the 2007 BMW 335. The most recently reported issues are listed below.
I was turning on to a highway, as I accelerated to match the speed of oncoming traffic and merge, the engine power abruptly degraded. I had to swerve out of the lane to avoid an accident. The vehicle had a flashing service engine light and was not producing any power. I had the vehicle towed to park Ave. BMW in NJ. The dealer diagnosed my vehicle with a failed dme (engine management computer or ecu) at less than 60k. After doing some research I found many others BMW n54 engine owners online who had encountered the same dme failure. It turns out an electrical component that costs a couple of cents was prematurely failing. This was known to BMW in 2007 when the vehicle was being sold. The BMW service builtin si b 12 18 07 clearly indicates that this is an unexpected failure and is caused by a defective diode. Further more the issue can damage coils and fuel injectors costing thousands of dollars. Replacing coils, injectors, and the dme can exceed $5000. Further more BMW chose no to be proactive and replace the component, instead they put peoples lives at risk, at best their benefiting from their own lack of quality.
The thermostat was failing to cool the vehicle under extreme heat conditions (over 100 degree days), took vehicle in to check the thermostat, but it was only a 90 degree day when they looked at the car, and were "unable to reproduce problem", so they returned the vehicle. About 6 months later, I took vehicle in to check the thermostat when the vehicle was unable to warm up under extreme cold conditions (under 30 degree mornings). Again, "unable to reproduce problem" because when the mechanics got to work in the morning, the temperatures were over 40 degrees. Other than extreme conditions, the thermostat seemed to work fine. But the following year, on a cold morning, not only did the vehicle fail to warm up, but the "check engine" light came on. By the time I was able to make an appointment and bring the car in, the light had gone out, and again, the service dept. Was unable to determine what made the "check engine" light come on. They said it must be an "intermitent problem". Yes, it was!! and the light came on another time, but I was out of town, so that by the time I got back, again it had gone out. The problem finally got bad enough for the light to come on again, and this time I drove the vehicle directly to the dealership w/o turning it off, so they could determine the problem. They finally confirmed there was indeed a problem with the thermostat, like I had told them all along, and they replaced the thermostat. When I got home and checked the internet, I found many complaints about this same problem with my engine in this model BMW. And BMW has not made a recall to to repair the item. This is a known and frequently recurring problem that BMW should be made to pay for &/or reimburse customers for expenses they incurred in fixing the problem, just like the fuel pump and battery problems for this same model vehicle that were fixed under recalls!!.