Since I have my gas tank on the ground (I'm replacing the sending unit), I probably should go ahead and clean it out before putting it back on the frame. What should I flush the tank with to clean it?

I did a fair amount of research before doing my own tank last summer. Start with water and dish detergent and a half-gallon of cracked gravel or old nuts and bolts, something that will slosh around and loosen any crud that's sticking to the inside. I used the lid from a soup can with the old gasket to cover the sending unit hole, and a rubber cap for PVC from the hardware store to cover the filler opening. Put the tank on a stable surface (I used saw horses) and roll it over and over to slosh things around really good. 15-30 minutes of sloshing to get all sides cleaned up should do it. Then drain the water and gravel out, making sure to get ALL of the gravel or hardware out of it. Rinse well, then slosh using mineral spirits to displace any residual water. If the tank was in relatively good shape to begin with that may be enough to keep it happy for a while. That's all I had to do with mine. If you still have surface rust, you might consider treating the tank with acid, but learn all you can about that before proceeding, or find someone who has done this before. It can be very dangerous working with acid...I decided I'd rather not go there, but it sounds like phosphoric acid is the best type. Do a web search under derusting and you'll find some good information on working with acids, just pay particular attention to the hazards and protective equipment, acid burns are not pretty! Finally, some people have mentioned coating their tanks to keep them from rusting inside in the future, but I talked to a local motorcycle shop owner who said he's seen a number of bikes come back after a few years with the coating plugging up the carbs...seems to me if the tank is that bad, a new tank might be the best bet. I priced out tanks and found the prices ranged from $250-$750. Hope this helps.

MTSteve

well, the water/detergent sounds good, but I don't know about putting in gravel. It would be tough going trying to get all of it back out, because my sending unit hole is in the middle of the tank. It would be like trying to get a pick out of a guitar hole. I'd have to toss the tank around, hoping the gravel ends up in the middle to fall out.

My tank is poly-something (plastic) so I don't have the rust concern. I think I'll just spalsh around the soapy water and be done with it.

Thanks for the info.

I'd throw a hand full of iron nuts in there and swish them around and use one of those telescoping magnets to fish out the ones that won't 'drop out'.
You can also use alcohol after the detergent since it has an affinity for water, and if there's still a cupful left in the tank it won't hurt anything after filling it back up with gas...

-D.Idiot

great idea!

Would a rusty gas tank be a good candidate for electrolysis rust removal? I guess once you pulled it out you'd have to seal it with something right away to make sure it doesn't start again.

_________________
Grip it and rip it

As an alternative to putting loose nuts and bolts in the tank for agitation, I use a length of clean chain. This way, you don't have to fish out seperate loose items. I recently installed a junk-yard tank in my 64 dart. After cleaning the tank similar to the descriptions above, I installed a transparent fuel filter with changeable filter elements. This way, I was able to visually monitor the condition of the tank. After the first couple of tanks fulls, the filter turned an expected rusty-orange. I changed the filter element and it has run pretty clean since. Good Luck -shane

chains are what i used in mine along with some gas, i heard of some using diesel but havent tried that....