e30 - what is this hose?

[EastCoastErik]

Mine has rotted. I can't figure out what it is. Does anyone know the part number? Hose Diameter? Anything?

[Vincenze]

It's a fuel tank ventilation hose.

https://www.realoem.com/bmw/enUS/showparts?id=1113-USA-02-1991-E30-BMW-325i&diagId=16_0107

I believe <1987 cars had fuel pumps with 2 outlets.

[aryahmmr]

yup, it's the fuel tank ventilation hose. Connects to the expansion tank, which connects to the charcoal canister, which removes unburned fumes from the intake manifold

[Panici]

See attached diagram for fuel tank vent routing. (Euro model).
Number 7 goes to the charcoal/evap canister on the north american models.

Bonus diagram of how I deleted the expansion tank in 2018.

[aryahmmr]

See attached diagram for fuel tank vent routing. (Euro model).
Number 7 goes to the charcoal/evap canister on the north american models.

Bonus diagram of how I deleted the expansion tank in 2018.

nice delete of the expansion tank. I'm thinking of doing it, but what are the repercussions? How has your car been running since the delete?
Also, there's a line between the feed hose (9) and the return hose (10) that is unlabeled. It's the one you've connected to the discharge hose (7) to in your bonus diagram. Where does this line go?

[Panici]

nice delete of the expansion tank. I'm thinking of doing it, but what are the repercussions? How has your car been running since the delete?
Also, there's a line between the feed hose (9) and the return hose (10) that is unlabeled. It's the one you've connected to the discharge hose (7) to in your bonus diagram. Where does this line go?

That's the main tank vent line.


Downside of the mod is reduced fuel tank capacity. I haven't measured the change, but it can't be a lot.
Gas tank still fills up to ~an inch of the top, as I found out when I worked on my fuel pump with a full tank.

Not a big deal for me, I'd rather not have liquid fuel just sitting in a plastic tank above my rear wheel anyways. No difference in running that I've seen.


Technically there is a risk of raw fuel backing up the vent line and contaminating the charcoal canister. I've never had this happen even with a full tank that is sitting in the sun. But I also make sure to not cheat the pump shutoff to squeeze extra fuel in the tank.

[aryahmmr]

That's the main tank vent line.


Downside of the mod is reduced fuel tank capacity. I haven't measured the change, but it can't be a lot.
Gas tank still fills up to ~an inch of the top, as I found out when I worked on my fuel pump with a full tank.

Not a big deal for me, I'd rather not have liquid fuel just sitting in a plastic tank above my rear wheel anyways. No difference in running that I've seen.


Technically there is a risk of raw fuel backing up the vent line and contaminating the charcoal canister. I've never had this happen even with a full tank that is sitting in the sun. But I also make sure to not cheat the pump shutoff to squeeze extra fuel in the tank.

awesome man, thanks for the reply! I, too, wouldn't want liquid fuel sitting in a tank above my rear wheel, but the engineers designed it like so. Anyways, I'm going to delete the expansion tank and see how it goes. Thanks for the diagram and the info