[bobzbeemer95]

Has anyone had this problem? I have a 1995 Bmw 525I. Love it and I've only had minor problems with it.
However yesterday when I was driving home from Tucson Az. I noticed a gas smell inside the car. I had just filled the tank in Tucson before heading home. When I got the car in the garage at home and got out--it sounded like the gas tank was boiling. It was making a loud burping sound--like a pressure build-up trying to release. I opened the gas cap cautiously and a lot of air was coming out. In fact the air didn't stop coming out for several minutes. After the air finally stopped I looked down the gas filler hole and noticed that an O-ring had slipped sideways and was keeping the little spring door open a little. I got it back in place. I haven't driven the car since. Am I driving a bomb? I've checked all under the car and took the back wheel and mud guard off to inspect the expansion tank for leaks but no signs. Has anyone else had this problem? I found only one mention of this problem on another site and the guy said that when he asked his Beemer mechanic of 28 years about it--the mechanic was stumped. Never heard of this problem in all his years.
I forgot to mention--the day this happened--it was over 100 degrees.
Besides this problem, the car seems to be running ok--maybe a little sluggish but not major. I'm stumped too!!!
Thanks for any suggestions or further clarification.

 

[bobzbeemer95]

Thanks for the reply,, but my problem is just the opposite.
My gas tank doesn't have a vacuum--it's under pressure. When I opened the gas cap it filled the garage with gas fumes. Had to open all the doors and gladly the wind was blowing that day.
One thing though, I remember now that the bubbling or boiling sound was coming more from the left side near the rear wheel. My Bently Manual doesn't show anything there. I'm going to remove the left rear wheel and mud guard this morning and see if anything is under there that is plugged. I'll let everyone know.

 

[bobzbeemer95]

I still haven't found the charcoal caniser and vent pipe yet. It's not on the passenger side of the car under the fender well---the same place the expansion tank and I couldn't find it under the hood anywhere. It doesn't show where it is my Bently Manual. I guess I'm going to have to take of the left rear wheel and mud guard and see if it is there. Just had too much to do this morning.
Thanks Marti for your input--I use that OEM Beemer site a lot.
I did drive the car today several miles and when I stopped--I opened the gas cap and--"no pressure in the tank". Of course, it's not that hot today.
So--will check for the canister this evening.

 

[bobzbeemer95]

I finally found the charcol canister. It's in the engine compartment just behind the driver's side headlight.
I also found that the symptoms of a bad canister is--"too much pressure in the gas tank and gas smell on hot days". Go figure.
I'm going to order the part from Bararian Autosport for $80.00. Hope that's what the problem is.
The following link is the only other reference I found that resembles my problem.

Charcoal Canister Location/Replacement [Archive] - bimmerfest - BMW Forums

When I get the part and get it on and it works I will let everyone know.

 

[bobzbeemer95]

Hey guys--& girls too if any--
Thanks for your input.
I still haven't fixed my problem. I did find the charcoal canister finally but didn't have the time to do anything about it. It's buried behind the left front headlight and under the power steering reservoir. I finally got it off today. I wish BMW manual would say how you can tell if the canister is bad or not. I can blow through either one of the tubes on top and nothing is plugged. As far as I can tell, there is no way this could be causing the back pressure in my gas tank.
The other day—I had to drive about 70 miles to Tucson again—on a hot day—and when I got there I could smell gas again. I got out and opened the gas cap a little and “nothing”. However, when I pushed my finger inside an opened that little metal door inside the fill spout—gas came blasting out of the tank and wouldn’t stop. I had to quickly put the main cap back on to get it to stop. I waited a few minutes and opened the gas cap just a little this time and the pressure vented for 5 minutes—and still didn’t stop. I finally gave up and drove home, hoping I didn’t blow up.
I’m going to bypass the canister today with a copper loop and drive for a while and see what happens.
The only other thing I found as part of this venting system is—on the outlet side of the canister—the hose goes to some kind of check valve with an electric wire attached. But I can’t find anything online or in my Beemer Manual as to what it is or how to check if it’s bad. When I blow through that hose going to the check valve-- it’s letting air through and if I suck on the hose the valve is closed.
Does anyone have any other suggestions? If I ever find what has gone wrong I’ll let everyone know.
Bob.

 

[bobzbeemer95]

Well—I finally figured it out my excessive gas tank pressure problem.
I took the right rear tire off. I removed the stone chip plastic guard from the fender well and exposed the fuel expansion tank. I traced the line from the charcoal canister up by the left front fender-- back to the top of the fuel expansion tank so I was sure I had the right hose. I then removed that hose from the expansion tank and put the end of it in a jar with a white paper towel. Then I removed the same line from the charcoal canister in the front of the car. Next I used my air compressor and blew air from the front to the back and into my makeup jar with the paper towel. I couldn't believe the crap that came out of the line, plus what looked like a small rock. “Where did that come from”? The line was plugged but its clear now!! Anyway—that fixed the gas tank pressure problem. I don’t have the gas tank pressure problem or bad gas odor anymore.

1995 BMW 525I