Gas smell/spilling?

[hsheeran]

Hi y'all, so I've been getting a strong gas smell in the cabin after 1. turning hard on the twisties or 2. filling up the tank past 3/4 full. If the tank is half or below and I don't rip around, there is no smell.

I replaced the o rings on the fuel tank sending unit, which another "gas smell" thread told me to do. I'm glad I did it, but it didn't fix the problem.

What do we think it could be, and/or what do you recommend I start pulling off to look for the culprit?

Thanks!

[mxl556]

First, I'd check for obvious leaks underneath the car (check tanks carefully as they may leak from that welded ridge connecting upper and lower half. Most likely it is vent hoses on top of both tanks that are leaking. To check for vent hoses, I'd follow the diagram from realoem. Start by removing the back seat and that hatch so you can easily see some of these hoses. In order to replace them you'd need to drop or at least lower both tanks. I'd use BMW 8x13 hose (if I remember it is the size, but double check before ordering).

[sonomaGTLN2]

I 2nd the comment about vent hoses. I had a persistent leak at the top of my tank and it turned out to be the tank itself had a stress crack at the vent hose fitting. Dropping the tanks really is not too difficult. Two nuts on the front of each side and the back mounts are slotted and the tanks slide right out.

[hsheeran]

Thanks, I'll investigate the hoses!

[gsumzzz]

Also double check the sending unit o ring sealing. A new o ring will swell after installation and with subsequent gas/fumes exposure. Do not reuse an old seal if u can help it. The metal seat can be warped if someone with meat hands worked on it in the past. This is a bit of a finesse job. Good way to check is to fill with gas til topped off and then get the rear bouncing to some effect. See if that o ring is really sealed. U may get some pooling around the seal area. Same effect as taking a curve on a full tank. Be very careful of the potential fire hazard. Disconnect the battery. Good luck.

- - - Updated - - -

Two seals to check. Sending unit itself and internal fuel pump mount assembly.

[hsheeran]

Also double check the sending unit o ring sealing. A new o ring will swell after installation and with subsequent gas/fumes exposure. Do not reuse an old seal if u can help it. The metal seat can be warped if someone with meat hands worked on it in the past. This is a bit of a finesse job. Good way to check is to fill with gas til topped off and then get the rear bouncing to some effect. See if that o ring is really sealed. U may get some pooling around the seal area. Same effect as taking a curve on a full tank. Be very careful of the potential fire hazard. Disconnect the battery. Good luck.

- - - Updated - - -

Two seals to check. Sending unit itself and internal fuel pump mount assembly.

Aha. When I ordered the O rings, it came with 2 of them of same or similar size, and I was like WTF is this second one for? Perhaps it is the pump O ring. I only last year replaced the sending unit O ring. Is it easily accessible with the sending unit removed?

What I did today is drained the tanks and lowered them halfway. I confirmed that the smell is coming from the sending unit area--it doesn't smell like fuel underneath the car at all. I looked at all the hoses and what I can see of them looks really nice, like maybe they had been replaced in the past ten years or so. No cracks or holes. What I can't see of the hoses, well... not sure how to see those! That braided one goes into a place I have no idea how to check... Is there a particular hose to look for? Or other tests I can do with the tanks lowered?

Thanks!

IMG_9459.jpg

[mxl556]

Hoses do look good. 2 o rings are: the larger one is for the pump unit that goes into the tank and the smaller o ring is for the sender unit (fuel gauge) that fits into the fuel pump housing.
I think one the braided hoses you can't see goes to a driver's side tank, on top. That one can leak enough to smell but is not pressurized, so it won't be obviously leaking from under the car. The only way to see its condition is to lower the tank. May as well replace it then. And if i remember correctly, another braided hose is going to the trunk and connects to the expansion tank on the passenger side.

[Brob]

I would probably drop the tanks and change out the hoses. I didn't find it too difficult or expensive when I did mine. The only hose that could cause you trouble is the threaded hose that might be difficult to remove and will need a new slip ring and nut to tighten it down properly. I had to do this to pass smog in Calif. My hoses were also 40 years old and not in great shape. Good luck

[hsheeran]

I would probably drop the tanks and change out the hoses. I didn't find it too difficult or expensive when I did mine. The only hose that could cause you trouble is the threaded hose that might be difficult to remove and will need a new slip ring and nut to tighten it down properly. I had to do this to pass smog in Calif. My hoses were also 40 years old and not in great shape. Good luck

I'll do the O Rings again. Are these the hoses I need? https://www.realoem.com/bmw/enUS/sho...diagId=16_0070

[Brob]

Yes, these are the hoses. #4 is sold by the meter and one meter isn't enough. I also bought new#5 and #6 connectors Also if you have the tanks out you might consider replacing the hose that connects the tanks together. It's a pretty heavy duty hose but one you don't want going bad.

[mxl556]

There is also a hose for the filler pipe, I'd replace it as well.