Does your fuel tank build pressure when hot and low on fuel ?

[Derek A.]

Filled up today. Car has always vented when I take the gas cap off. Moreso when its hot out and the fuel is low- Is this normal ? Have noticed a fuel smell in the garage - not sure if its the BMW or not.

[Rus]

Mine does this almost every time. Most older cars seem to build up some pressure and I think it may be due to the less advanced fume control system that most of them had.

[Derek A.]

I got home and it looked like fuel was dripping from the left hand side of the tank... ideas ?

[shogun]

I have no magic eyes, why do you not have a look under the car.
Fuel tank
http://www.realoem.com/bmw/showparts.do?model=HD23&mospid=47408&btnr=16_0187&hg=16&fg=05
Maybe something wrong with ventilation or return line system
http://www.realoem.com/bmw/showparts.do?model=HD23&mospid=47408&btnr=16_0078&hg=16&fg=10
check these hoses and connections. In case of my car I have to remove the rear wheel right side, then the plastic insert under that fender, then you see the expansion tank and the hoses. I replaced them all
http://www.realoem.com/bmw/showparts.do?model=HD23&mospid=47408&btnr=16_0103&hg=16&fg=10

[Paul in NZ]

i frequently run my car from full right to empty ie light may be on fr 40 or 50 km.I have never noticed any "venting" but i am not 100 per cent sure we have the same fume control system at all.

[whiskychaser]

Filled up today. Car has always vented when I take the gas cap off. Moreso when its hot out and the fuel is low- Is this normal ? Have noticed a fuel smell in the garage - not sure if its the BMW or not.
Think what you hear is more likely air rushing in than out-caused by a slight vacuum in the tank. Makes sense if you start off with the air above, say 3/4 tank and then pump out 1/2 tank you will be left with less air pressure inside than out. If its serious your tank would crease inwards. Remember petrol caps used to have vents to prevent this but these days the systems must be much more clever

[RobPatt]

...in the summer...

get in after work, cars in the 100s F scale...hot...

got a quarter tank... can go a few days on that....

whoops.... tank cools w/air from driving... next thing I know I'm on vapor.

crap..it's been about 400 miles... guess i better get some gas.

[Milkboot]

I get that smell mainly when over half a tank. its rather anoyying :( dont know what is causing it just yet because i havnt been able to reach the res tank to check it

[Derek A.]

What is the pain in the ass factor in getting that wheel well out?

Car is now dripping fuel from the muffler area. Going to have to park it until I can get a look.