Fuel smell, vent tanks and valves

[itchyfeet]

the poptop has had a fuel smell since I had it, it's much worse in summer, in winter it's ok, I have replaced the filler neck and the hoses to the tanks but what I didn't realise until recently is there is a float valve in the top of each tank.

I took the tanks off today and found that I can blow and suck through the pipe to the valve so it's venting ( I assume if there was liquid in the tank it would close), there should be a valve on the end of the pipe too part number 321201890 but they are both missing, one can be seen split and sitting on the tank on the last picture.
These are described as gravity valves so I assume they stop venting normally.

I ordered some replacements but does anybody know if this is enough to cause a fuel smell?

thanks

P1080973 by Paul_Barr, on Flickr

P1080995 by Paul_Barr, on Flickr

[tonytech]

The tanks in the wheel arches are "expansion tanks" designed to cope with the U shaped main fuel tank. I believe the valve on the top seal if the van turns over,
The ears on the end of the pipes often get lost, their main task is to stop dirt getting into the system. I dont think they are valves. (on USA models with stricter emmissions, they vent into the intake system)
The usual reason for fuel smells is degraded fuel lines (modern fuel rots old rubber lines) or a rusted tank... dirt and water get trapped on the top...

[937carrera]

I assume you've read this

https://club8090.co.uk/forum/viewtopic.php?f=37&t=162534

If you want to check the operation of the float valve I think you might need to remove it from the overflow tank and move it manually I'm thinking the valve should be normally closed, and only open when the float opens the valve. (otherwise there would be permanent fuel evaporation)

[itchyfeet]

I assume you've read this

https://club8090.co.uk/forum/viewtopic.php?f=37&t=162534

If you want to check the operation of the float valve I think you might need to remove it from the overflow tank and move it manually I'm thinking the valve should be normally closed, and only open when the float opens the valve. (otherwise there would be permanent fuel evaporation)

thanks
thats my question, are you sure of the answer?

[937carrera]

Not certain of the answer, sorry, but if it was the other way round then fuel would vent to atmosphere when parked up and the only purpose of the valve then would be to stop fuel exiting down the pipe when cornering.

The reason I looked at my pipes was because a) I couldn't fill the tank without leaking, b) I parked the van up on the right hand side of the reserve line, when I next went to start it the level was almost down to the left side of reserve. Missing / deteriorated /disconnected pipes being the cause.

You have two to test / corroborate / break as you remove them

[bigherb]

I took the tanks off today and found that I can blow and suck through the pipe to the valve so it's venting ( I assume if there was liquid in the tank it would close), there should be a valve on the end of the pipe too part number 321201890 but they are both missing, one can be seen split and sitting on the tank on the last picture.
These are described as gravity valves so I assume they stop venting normally.

I ordered some replacements but does anybody know if this is enough to cause a fuel smell?

thanks

The valves only close when inverted to stop fuel leaking if you roll over, otherwise they vent both ways to let pressure out when the fuel expands due to ambient temperature changes/hot fuel returning from the engine and to stop a vacuum when the fuel is used. There isn't a valve on the end of the breather it is just a moulding to stop the pipe ends sitting on the top of the tank and getting blocked.

[937carrera]

Good to know - I hadn't considered putting a T25 on its roof

[itchyfeet]

VW T25 rotation by Paul_Barr, on Flickr

what I don't really understand is why a vent pipe cracked or perished should be any worse thatn the fumes coming out of these pipes unless its petrol sloshing around coming out of perished pipes further down.

[Jim San]

There's a certain dodgeyness about the hub cap in the top pic

[937carrera]

Nice picture - should make repairing the sills easier

You're right, of course, except from a design perspective the assumption is that the pipes from the tank to the overflow tank are assumed to be in good condition, so the valve is only needed as a safety feature in an accident when the vehicle is inverted and fuel could flow out of the vents, similar to electric fuel cut off valves on carbs cutting off the supply. I'm actually kicking myself a bit for not thinking about this - I had heard about it before.

I'm not sure that this information helps with your original fuel smell issue, is it worth checking that the 4 pipes to the tank are still connected and the fuel lines are not weeping ?

[937carrera]

There's a certain dodgeyness about the hub cap in the top pic

I see what you mean

In the second pic I can also see the missing trombone, cracked as usual which is why it has fallen off

[itchyfeet]

There's a certain dodgeyness about the hub cap in the top pic

[CovKid]

Brings a whole new meaning to "hanging out in the VW scene"

Mind you, who wouldn't get excited playing with expansion tanks.

[itchyfeet]

Is it possible to change the inner breather rubber pipes without dropping the tank?
the one to the balance pipe looks accessible (16 on link ) but not sure about the one to the rear vent pipe.( 15 on link)

there don't appear to be any clips

http://www.realoem.me/Volkswagen/RDW/T2 ... /201/32000" onclick="window.open(this.href);return false;

[937carrera]

It "is" possible, and by the looks of things many people on here have done it.

When I did it I was on a ramp and dropped the tank completely down as I wanted to inspect the top anyway. You need height to get the supporting bars clear and out of the way. I prefitted hoses "15" to the metal pipe, plastic connector and the hose again (with a little extra length) and similarly "16" to the grommets "6". You should therefore remove the grommets from the tank before dropping it on mine the cross pipe "1" is secured to the underside of the chassis with a P clip type arrangement. That isn't shown on the picture. With everything assembled you then have to force the grommets back into the tank. I used a bit of WD40 to lubricate and it's awkward to get the force at arms length.

If you aren't going to drop the tank then I would say it is certainly possible, but it's fiddly reaching through the chassis even with the wheel removed to get the hoses in position. One of those jobs that is much easier once you have done it. Have a swear box handy if you like