Paging mercmad - Cutting a tank open

[helgathe109]

Posting a public message instead of shooting you a PM in the hope that somebody else may find your response useful in the future.

I got your reply on FB, and I've also found another post of yours on this exact topic on the peachparts forums...

I'm at the point now where I need to cut a hole in the top of the fuel tank on my MFI W109 (I'm guessing this will apply to W108 owners also).
The largest holesaw I can find is a 6" saw from bunnings.. will this be large enough to get at the swirlpot? If so, is there a specific location on the top of the tank that I should aim for that will give me the best chance at cleaning the swirlpot properly?

Secondly, I'm assuming the swirlpot will need to come out before I can coat the inside of the tank with a rust preventing sealer. Will it fit through the 6" hole?

Thanks in advance for your help on this one Ron.. and for your help over the last few days, much appreciated !

[Bartman4800]

Be absolutely sure that you removed any residue of petrol or the gaseous form thereof (much more dangerous). One little spark and boooooooooom!!!

Wash out the tank with water several times before you start cutting.

I think Ron just uses an angle grinder, but once he comes online he can tell you himself. Use a thin disk as this makes the later weld gap smaller; reuse the original piece if you can.
Make the hole large enough for you hand to get inside and then some.

Take the fuel filter first out of the bottom, you can make up an internal hex from a bolt welded to a nut.

Regards, Bart

[helgathe109]

Be absolutely sure that you removed any residue of petrol or the gaseous form thereof (much more dangerous). One little spark and boooooooooom!!!

Wash out the tank with water several times before you start cutting.

I think Ron just uses an angle grinder, but once he comes online he can tell you himself. Use a thin disk as this makes the later weld gap smaller; reuse the original piece if you can.
Make the hole large enough for you hand to get inside and then some.

Take the fuel filter first out of the bottom, you can make up an internal hex from a bolt welded to a nut.

Regards, Bart

Thanks Bart, I was thinking the exact same thing re the grinder (was actually thinking of cutting a large rectangle out of the top and almost taking the "lid" off), however Ron's post on the peachparts forum specifically states not to use a grinder, so here I am with my questions! haha

[helgathe109]

PS.. where can I find more pics of the car in your avatar Bart? I absolutely love that colour.

[konrad]

Far be it for me to give anyone advice on anything but........I was always taught that you only cut a fuel tank when it is FULL of water and therefore no fuel/oxygen mix to ignite. Yes/No

[Bartman4800]

Far be it for me to give anyone advice on anything but........I was always taught that you only cut a fuel tank when it is FULL of water and therefore no fuel/oxygen mix to ignite. Yes/No

That is the rule for farmers, normal people can flush the tank

Another option (seriously now) is to fill the tank with an inert gas: Helium, Argon, Co2, or for farmers: Hydrogen

[konrad]

That's what I said.
Fill it with hydrogen (2 molecules) and oxygen (1 molecule)

[Bartman4800]

This is a link to an older discussion where Ron suggested what to do:

viewtopic.php?f=9&t=15001&p=105840&hili ... NK#p105276

Regards, Bart

[Tony From West Oz]

Carbon monoxide is relatively inert and will not support combustion.
Just get a petrol fueled car and poke the exhaust into the tank filler pipe before using the angle grinder. Do not use Oxy acetylene to make your cuts, as CO will combust with excess O2, as will any remaining petrol vapours....BANG!!!

Good luck,
Tony

[konrad]

Or.........just fill it with WATER.
Easy, Safe, Clean, Freely Available.
Why would one eff around with inert gasses, cleaning, de-gassing, petrol motors etc, etc?
Just fill it with H2O
.

[Mercmad]

i use a hole saw, about 6" dia. It's easier to weld it back together then and can leak free. filling with water is the easiest although you can stick weld diesel tanks while they are still full of diesel.
It's when you have air in the tank that trouble strikes. So make sure you flush the tank out first with engine degreaser ,then fill it completely with water. When finished ,without leaks, pour a liter of methylated spirits into the tabk and slosh it around .
leave the tank in the hot sun to dry it completely.