At Roebling last weekend I had gas coming out of the filler port region. I could smell it and drivers behind me reported it. One sent me a video and it really looked like it was coming out of the filler port door.
Over the course of the weekend I tried 2 other gas caps and didn’t really beat the problem. “Maybe” one of the caps reduced the problem, but nothing beat it.
The problem really acted like the filler cap wasn’t on properly, but the cap was on just fine. All 3 of the caps were on securely. My thought was the the loop of hose, right next to the end of the filler spout, was the problem. It’s the one rubber piece closest to the filler door, or so my thinking went.
My plan is to simplify things a bit. If that doesn’t beat the problem, at least there will be fewer possible culprits. I’m going to plug and/or remove the 3 connections to the expansion tank. The rules don’t support removing the tank itself, so it needs to stay in place even tho it will be inop…
I pulled the expansion tank from the RR well and examined all the hoses carefully. The 2 little tubes looked fine. The 14mm hose looked bad but serviceable. The little loop tube by the filler port looked fine. I removed the 8mm tube that goes to the engine bay carbon canister, I’ll plug the 6mm tube that goes to the expansion tank, and I’ll replace the 14mm hose that went to both filler port and expansion tank.
So if I get another leak problem, it pretty much has to be the gas cap. I also bought 2 of them, one vented (my usual) and the other not vented.
I noted that the RealOEM diagram doesn’t properly depict the 6mm tube at all. Mine certainly does not connect next to my fuel pump, as the diagram shows.
https://www.realoem.com/bmw/enUS/showparts?id=1113-USA-06-1987-E30-BMW-325i&diagId=16_0107