89 635 Gas Tank Brain Teaser
Yesterday here in Las Vegas it was hot (108F) so I was travelling across town with the air conditioning on in afternoon rush hour traffic -- lots of stop/start traffic. Wanting gas, I stopped at a service station, turned off the air conditioning first and then the car. Opened the refueling door and as I unscrewed the gas cap, pressure from the tank pushed the cap away from the filler tube. Looking down the filler tube the gas was bubbling (like it was cooking or boiling) and you could feel pressure comng out of the tube. It continued to do this for a good ten minutes. When it stopped bubbling I elected not to fill the tank, replaced the cap, drove the five minutes to the house, parked it in the driveway, opened the gas cap and hood and let it sit for an hour while I called my mechanic with 28 years of Beemer experience. He said that he never heard of such a thing but will check through his contacts. I, in turn, thought I'd try this forum to see if anyone else ever experienced this.
To Recap: outside temp was 108F; air conditioning was on; heavy rush hour traffic with numerous stop/start situations; semi aggressive driver; gas tank was half full at the time; no indications on any of the gauges that anything was going wrong; when unscrewed gas tank pressure forced the cap away from the filler neck; bubbling gas was observed in the filler tube and lasted about ten minutes.
Anyone got a clue???????