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twin tank breather pipes
https://www.ausmini.com/forums/viewtopic.php?f=2&t=45853		 Page 1 of 1
Author:  Bubbacluby [ Wed Sep 17, 2008 10:32 am ]
Post subject:  twin tank breather pipes
Dad just installed twin tanks in his mini and i told him he needed two breather pipes. I just cant find any photos of when i dismantled my GT of where the pipes go.

I know there are two and they attach at the top of the tanks and go across to the other tank along the parcel shelf and down the side next to the tank and then out the boot floor. I just dont know where they go from here??

what do you do with the pipe hanging out the floor on each side??

Thanks Brenton
Author:  Mick [ Wed Sep 17, 2008 10:36 am ]
Post subject: 
That's it, they just swing in the breeze down there...
Author:  66S [ Wed Sep 17, 2008 12:22 pm ]
Post subject: 
Hi Brenton,
If your car is a Aussie one, the pipes do cross, the right vents through the floor via a special hole and gromment, adjacent to the battery cable grommet and the left one vents through the fuel gauge sender cable grommet. They protrude through the floor by about 3 or 4".

I believe from around mid '66, English S vent pipes didn't cross, left vented left and right to right.

Regards
Al
Author:  Panthersteve [ Wed Sep 17, 2008 12:27 pm ]
Post subject: 
66S wrote:
Hi Brenton,
If your car is a Aussie one, the pipes do cross, the right vents through the floor via a special hole and gromment, adjacent to the battery cable grommet and the left one vents through the fuel gauge sender cable grommet. They protrude through the floor by about 3 or 4".

I believe from around mid '66, English S vent pipes didn't cross, left vented left and right to right.

Regards
Al


Hi

I don't know if I have misread this but the 2 options above seem to be the same :?

It says the pipes cross but also says the right vents on the right (near battery) and the left vents on left (through sender cable grommet), how do the cross but still vent on the same side as they originated :?:

Cheers
Steve
Author:  sitnlo62 [ Wed Sep 17, 2008 12:56 pm ]
Post subject: 
66S wrote:

I believe from around mid '66, English S vent pipes didn't cross, left vented left and right to right.

Regards
Al


The reason these vent pipes cross is to prevent fuel syphoning out onto the ground through the vent pipes when the car is parked on a slope with one tank higher than the other :idea:
I doubt that the factory would have made a mistake like that.
Dave
Author:  66S [ Wed Sep 17, 2008 1:07 pm ]
Post subject: 
Panthersteve wrote:
Hi

I don't know if I have misread this but the 2 options above seem to be the same :?

It says the pipes cross but also says the right vents on the right (near battery) and the left vents on left (through sender cable grommet), how do the cross but still vent on the same side as they originated :?:

Cheers
Steve


Yeah, I'm a confusing bastard! What I was referring to above is the vent pipes, right being the one from the left tank etc. So, to clear it up, the right tank vents to the left, through the sender cable grommet and the left tank vents to the right, through a special hole and grommet.

English cars from around mid '66 vented left to left, right to right.

Regards and sorry!

Al
Author:  66S [ Wed Sep 17, 2008 1:10 pm ]
Post subject: 
sitnlo62 wrote:

The reason these vent pipes cross is to prevent fuel syphoning out onto the ground through the vent pipes when the car is parked on a slope with one tank higher than the other :idea:
I doubt that the factory would have made a mistake like that.
Dave


Hi Dave,
They obviously had a theory but changed their minds in '66. Think about this too, single tank cars vented on the tank side and never crossed.

Al
Author:  winabbey [ Wed Sep 17, 2008 1:53 pm ]
Post subject: 
66S wrote:
sitnlo62 wrote:

The reason these vent pipes cross is to prevent fuel syphoning out onto the ground through the vent pipes when the car is parked on a slope with one tank higher than the other :idea:
I doubt that the factory would have made a mistake like that.
Dave


Hi Dave,
They obviously had a theory but changed their minds in '66. Think about this too, single tank cars vented on the tank side and never crossed.

Al


Of course venting is not a problem with a single tank because the car would have to be laying on its side (!) for the fuel to reach the vent in that tank.
Author:  sitnlo62 [ Wed Sep 17, 2008 2:05 pm ]
Post subject: 
66S wrote:
sitnlo62 wrote:

The reason these vent pipes cross is to prevent fuel syphoning out onto the ground through the vent pipes when the car is parked on a slope with one tank higher than the other :idea:
I doubt that the factory would have made a mistake like that.
Dave


Hi Dave,
They obviously had a theory but changed their minds in '66. Think about this too, single tank cars vented on the tank side and never crossed.

Al

Al, sorry to contridict you but I would suggest it is more than a theory.
Physics is Physics and liquid flows down hill. It always has before and after 1966.

Think about what we are talking about, Two fuel tanks with a crossover tube which will equalise the amount of fuel in the two when they are on level ground.
The moment the car is sitting on uneven ground one tank fills into the other until the fuel finds its own level. In extreme circumstances the low tank can fill to overflowing from the vent pipe. the vent pipe must be routed across to above the top of the opposing tank to prevent the fuel from syphoning onto the ground.

Your argument about a single tank vent not crossing, I am afraid is totally without merrit.

Dave
Author:  66S [ Wed Sep 17, 2008 2:07 pm ]
Post subject: 
So, you think extending the vent pipe would make a difference?

I can see your point Dave but for some reason, it was dropped in England and that detail can be checked in the parts book. It seems the clips, spot welded to the underside of the parcel tray on English cars from early '66 were dropped around then too and I am guessing that is why Aussie cars stayed with the bolted clips, they wanted to stick with the cross-over venting.
Al
Author:  peterw [ Wed Sep 17, 2008 2:17 pm ]
Post subject: 
Quote:
The reason these vent pipes cross is to prevent fuel syphoning out onto the ground through the vent pipes when the car is parked on a slope with one tank higher than the other Idea
I doubt that the factory would have made a mistake like that.
Dave


I made that mistake with my first Mini in the 70's. After fitting a RH tank ($15 in those days) and parking on a road that caused the car to tilt down on the LHS, I came back to find a small river of petrol going down the gutter and half full tanks. The tanks always want to equalise due to the law of gravity, fuel flowed from the RH tank to the LH via the fuel line, filled the LH tank and sent it out the overflow.

They definitely need to cross over.

Pete
Author:  776vde [ Thu Sep 18, 2008 3:25 am ]
Post subject: 
UK built cars vented to the opposite side when twin tanks were fitted right up to the end of Mk 3 S production in 1971 - there was no change to this in 1966.

BMC were well aware of the problem if they vented to the same side and issued a service bulletin about it.
Author:  66S [ Thu Sep 18, 2008 6:03 am ]
Post subject: 
Hi guys,
I guess we need proof here, anyone got it?

Regards
Al
Author:  Convertible Mini [ Thu Sep 18, 2008 7:20 am ]
Post subject:  Interestin issue
This is a very interestin issue. Many times one walks close to a Mini with twin tanks and you can smell fuel fumes. especially if it has just had both thanks filled up. Perhaps this is an issue that everyone overlooks and we need to get some correct theories to correct the problem as it is a quite a hazardous one.
Author:  miniron [ Thu Sep 18, 2008 8:34 am ]
Post subject: 
The fuel smell can also be caused by faulty or incorrect tank cap seals. Especially if parked on an angle. Best not to use the rubber type cap seals as they can tear and/or bunch up when the cap is twisted on. The originals were a type of hard fibre material with IIRC some sort of graphite material impregnated into it.

RonR
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