Water in Fuel Tanks

[4129R]

It would be great if you could isolate it to one tank, by disconnecting the second one.  It could be a step toward figuring it out.  Is there any way to see the water in the tank?  You could just isolate them and have a look after a big rain storm (conceivably).  I don't know if you could try to run it on only one if you wanted.  Probably.

I can easily isolate 1 tank at the T piece which is a copper/brass compression gas T.

There is no way of knowing if there is any water in the tank until you drain it, then in a see-through container, you can clearly see the two liquids with a line where they meet.

[SilverBeast]

It would be great if you could isolate it to one tank, by disconnecting the second one.  It could be a step toward figuring it out.  Is there any way to see the water in the tank?  You could just isolate them and have a look after a big rain storm (conceivably).  I don't know if you could try to run it on only one if you wanted.  Probably.

I can easily isolate 1 tank at the T piece which is a copper/brass compression gas T.

There is no way of knowing if there is any water in the tank until you drain it, then in a see-through container, you can clearly see the two liquids with a line where they meet.

Can you poke a tube down to the bottom of the tank and draw some fluid from the bottom, which will be mainly water without having to drain the tanks? That way you could try isolating both tanks. You could possibly leave them empty and hose down the car and see if any water gets into one of the tanks?

Could the water be going round the seal round the filler neck in the bodywork, and getting inside the rubber hose from the filler neck to the tank from the top?

[4129R]

Can you poke a tube down to the bottom of the tank and draw some fluid from the bottom, which will be mainly water without having to drain the tanks?

A. Much easier to drain the tanks through the drain plug, just jack the back up, which gets all the water to run to the front where the drain plug is located. That way, all the water comes out.

 That way you could try isolating both tanks. You could possibly leave them empty and hose down the car and see if any water gets into one of the tanks?

A. I will remove the filler tops and the rubber hose connector to the tanks, and introduce resin to fill the tops of the tanks completely, through the 3" hole in the bodywork. 

Could the water be going round the seal round the filler neck in the bodywork, and getting inside the rubber hose from the filler neck to the tank from the top?

A. The hose connector is new and a tight fit, so no water can be getting into the tanks through the filler necks and caps. It must be getting in through the tank tops

[4129R]

I have been giving this a lot of thought.

If only one tank is leaking, there will be more water in that tank, water from the bottom of that tank up to the outlet pipe, and half the amount greater than fills up to that outlet pipe, with the other half flowing through the connecting pipe to the other tank.

If both tanks are leaking, and one is leaking greater than the other, I will only find this out after I seal the top of the leaking tank, or the tank that leaks more.

The right hand tank had more of the 1 pint in it, (there was very little in the left tank) so I will start by sealing the top of the right hand tank.

I further deduce that to fill an empty tank up to the outlet pipe needs just over 1 pint, which seems about right.

[Kendo]

You might consider mixing in micro balloons to make the patch lighter and stiffer and less runny, if that would help with application.

[Fotog]

If you haven't done so, how about just draining the tanks dry, isolating them, and see what happens when it rains?  You don't need to drive the car, right?  I would imagine only one is a problem.  Then take it out.  inspect it carefully, then if necessary test it with compressed air (not much, like from the exhaust of a vacuum cleaner) and a bubble solution to find leaks.  Need to plug that little breather nipple on the inlet, of course.

[GavinT]

If only one tank is leaking, there will be more water in that tank, water from the bottom of that tank up to the outlet pipe, and half the amount greater than fills up to that outlet pipe, with the other half flowing through the connecting pipe to the other tank.

Unlikely that both tanks would present as leaking at the same time IMHO.
If I've understood this correctly, yes, but I'm not sure what you mean by "fills up to that outlet pipe".

But interconnected tanks will certainly syphon both ways.
F'rinstance, assume there's, say, one pint of water accumulated in the left tank while the car has been parked over night.
(OK, technically, it'll start to syphon immediately the rain water starts to get in.)

If you now park the car on the right side of the road, you'll find the water has syphoned itself to the right tank. This assumes there's a reasonably steep crest in the road.
Similarly, if you then move the car to the left hand side of the road (facing the same way) you'll find the water has moved back to the left hand tank.

I recall going to a BBQ somewhere and parking on a slope. When I later stepped into the car to go home, I noticed the fuel was low but rose back to normal along the way.

There's also "Water Finding Paste". Our guys used this stuff to keep track of water ingress to an underground fuel storage tank we had, back in a past life.
Here's a link to an Oz product (and demo) but it must be fairly common.

https://www.fuelequipmentspecialists.com.au/water-finding-paste/

[4129R]

Water lies in the bottom. The outlet pipe is about 15-20mm above the bottom, so only water above 20mm will possibly pass through the pipe to the other  tank, but there is already petrol in the pipe so the water has to fight the petrol to pass through a pipe which is about say 4mm internal diameter.

So the leaking tank will have 20mm more water in it than the other tank.

[Fotog]

Maybe!   

[GavinT]

Oh, OK . . . 20mm off the deck.
I think my S2 has the pipes pretty close to the bottom of the tank.

Anyway, I reckon Fotog's idea has merit and should be easy enough to do without taking the tanks out.
What about making a wooden (MDF) bung for the filler neck and silicone it into place. Seal off any vent tubes and apply a little compressed air to the existing fuel line with your BA spraying the bubble solution.

Probably don't even need to drain the tanks, either.

[berni29]

Hi

A good way to find air leaks is with a smoke generator. No need to take anything apart, just seal off the entry point. Works great on modern induction systems with 101 pipes and connectors etc. A petrol tank should be easy!

There are quite a few youtube videos on making them. I have done that before, but now have a "cheap" Chinese made one. Was bought from Ebay or Amazon, cannot remember.

All the best

Berni

[4129R]

I decided to seal the top of the RH tank.

I removed the filler cap and the rubber tube to the tank top hole, covered the opening with the bottom 1" of a plastic cup (exactly the right size) and made a funnel from an empty orange juice bottle which was long and round, so when I cut it up, I was able to make it into a funnel shape.

500mm of resin was just a little too much to cover the whole top. It flowed evenly over the whole tank top without any need to spread it out using a long wooden spatula.

I surrounded the hole in the bodywork with masking tape in case of drips.

Time will tell whether the LH tank needs the same.

You can just see the bottom 1" of the plastic cup covering the big hole, above the Banks engine cover support bracket. The crescent to the left of it is the bottom of the plastic funnel I made up. 

[TurboFource]

On my one good tank, I primed, painted and undercoated the top of the tank while it was out of the car.
When I repair the other tank (in the future….) I think I will make the top flush with the sides to prevent this issue!