Thread: Fuel tank breather - did I just stuff up ?

John I will have a look at my tanks tomorrow as I have hoses off.
Cant be to much of an issue I would have thought as breather exits to main filler, probably Land Rover belt and braces design for if your on an exstreme slope or upside down but still can't see reason
Will look at mine and post

Cheers Paul

Thanks Paul, I'd like to know the purpose of the breather, and how it's supposed to work. I originally thought it was to let vapour out if there's a build up of pressure, but I now believe it's to let air in to replace the volume of fuel being used.

Any help appreciated.

Cheers,
John

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My tanks are non standard, aluminium but they have no obstruction in breather and car ran and functioned.


I understand your concerns as I overthink also (first resto) but the more I get into my car I'm amazed at how logically they are designed and sometimes over designed

Cheers Paul

I have two aftermarket fuel tanks on Betsy and they have no obstructions in the breathers either and the 2 standard tanks I also have lying around, dont have any obstructions either.

Cheers Rod

The breather allows the air in the tank out when filling otherwise with the nozel in the filler tube i& the fuel going in it westricts the exit & causes the automatic cut out in the nozle to cut the fuel flow. Also allows the tank to be filled to capasity if the filler tube goese in the side or below the top of the tank.

I think you are overthinking it a bit - automatic cutoff nozzles were unheard of when the Series 2/3 tank was designed. The breather is there simply because without it, particularly when the tank reaches full while refuelling, and especially if leaning a bit that way, the air escaping from the fuel going in has to come out the same hole as fuel is going in, so it is going to spit fuel back at you.

Venting for air to replace fuel as it is used, and with changes in temperature, comes in through the vented cap - except in the case of late model Series 3, where the venting is separate and via a charcoal cannister - but it still allows the air to come out separately from the fuel going in when refuelling.

With out the vent the fuel bubbles back the filler neck as the air tries to escape. This makes filling very slow.