You are right Dave... Breather is requirement.

Thanks Paul. No issues yet but I'll keep an eye on it. Might drill a tiny hole in the filler cap.

Mark
you will know if your breather is blocked. It lets air in as the fuel is used so you will possibly get fuel starvation on a run, it also lets the air space expand and contract with temperature so if you hear a rush of air going in or out of the tank when you remove the filler cap then you probably have a blocked (or no) vent.  Have seen tanks expand like baloons when parked in the sun when after market unvented caps have been fitted, alternatively it can push fuel into the carbs flooding the engine and make starting it pretty spectacular.

They can cause problems of their own though, many are just a bit of flexi pipe from the neck of the tank to under the car so can spill fuel as the car is driven with a full tank, raising the pipe above tank level before exiting the bonnet and fitting a decent valve will solve this. Not cheap decent ones, mine is a rally approved valve that lets air in and out but stops fuel in a roll over - Demon Tweeks.

Mark
you will know if your breather is blocked. It lets air in as the fuel is used so you will possibly get fuel starvation on a run, it also lets the air space expand and contract with temperature so if you hear a rush of air going in or out of the tank when you remove the filler cap then you probably have a blocked (or no) vent.  Have seen tanks expand like baloons when parked in the sun when after market unvented caps have been fitted, alternatively it can push fuel into the carbs flooding the engine and make starting it pretty spectacular.

They can cause problems of their own though, many are just a bit of flexi pipe from the neck of the tank to under the car so can spill fuel as the car is driven with a full tank, raising the pipe above tank level before exiting the bonnet and fitting a decent valve will solve this. Not cheap decent ones, mine is a rally approved valve that lets air in and out but stops fuel in a roll over - Demon Tweeks.

Thanks Dave. Think I'll drill that tiny hole in my original Beetle cap - is this a good idea? I've not had any problems so far - furthest I've driven is only 59 miles though.

Yes. Breather is required. I had a 1275 GT years ago and I broke down. Took the cap off and all ok. Replaced the cap broke down. Found the vent became blocked somehow.
There are vent in the VW tank. The only reason I had to make another was the tank I bought had been modified and sealed with POR sealer, and it must have blocked the vent.
DJ

Do you guys think a 3mm hole in the cap will do the trick? It's an original Beetle screw in cap, the type that clicks and spins once it's all the way in.

Don`t make the hole too large, or water will go in.

Flags has a really good arrangement on his cap - cannot find the picture though

If you are going to drill the cap, a hole 3mm diameter is far too big.

1mm diameter (maximum) will do it, as all thats required, is to achieve a balance...

Peter

Was just typing what Peter said. Air is thinner than fuel, just need a pinhole

Thanks guys. 1mm it is

If you are talking about the one on Raspberry Dave I fitted 2 small petrol safe 1 way valves as I had a problem of fuel pressurising the tank if left stood in direct sunlight, you also obviously need air in to prevent fuel starvation.  Tried a 1mm hole but stank whilst driving so drilled 2 holes and fitted the valves inside the cap, 1 each way.
Fuel will not leak as they need pressure to open and can't be seen when the bonnet is open.
Don't think I have any pictures though.

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I actually bought a vented filler cap and have never needed to worry about any additional venting at all. OK mine was a bit special and an expense I wouldn't repeat. But could be worth losing into a vent cap if you can.

If you are talking about the one on Raspberry Dave I fitted 2 small petrol safe 1 way valves as I had a problem of fuel pressurising the tank if left stood in direct sunlight, you also obviously need air in to prevent fuel starvation.  Tried a 1mm hole but stank whilst driving so drilled 2 holes and fitted the valves inside the cap, 1 each way.
Fuel will not leak as they need pressure to open and can't be seen when the bonnet is open.
Don't think I have any pictures though.

Yep - it was Raspberry I was thinking of - take some pictures as it was a brilliant solution 

Will do Dave but the valves were left over spares from an old genny set that had a hand pump primer we had in work but they look the same as windscreen washer pump valves which are made to work with screen wash so may be ok with ethanol.

I'll upload a picture at the weekend Zip Buggy

Thank you. Curious as to what the effect on my buggy would be without one.

The small black pipe (yellow arrow) connects to the pipe connector (yellow arrow) The neck with the red arrow came off an MX5. The 90 degree rubber pipe came off a Peugeot 106