Cleaning fuel tank

[WheelieKing]

I just bought a 69 d100. I siphoned the old gas out of the tank and there is some reddish gunk in there. I'm also getting it in my fuel filter. I tried draining the tank from under the truck until it seemed empty. I put a gallon of clean gas in to flush out crud but nothing came out the bottom. I'm trying to avoid removing the tank for cleaning. I'm planning to add a couple gallons and siphon it out a few times. Is there a better way to clean the tank without removing it?

[my5thmopar]

Welcome This is one of those jobs that you don't cut corners. It will take you longer messing around than to do it correctly. the reddish stuff might be Red-Kote but, it shouldn't come out unless it wasn't coated correctly. Remove tank and sender unit then drain and flush it. If that doesn't help and the reddish stuff.." IS NOT Red-Kote" then....Put a chain or rocks or something inside. Lay it on the ground then do the shake shake shake. Rinse out with gas or acetone. If it looks ok put it back in if not, buy another one or get some Red-Kote. Make sure you follow the directions and let the stuff dry. I've used it a few times without issue. Have fun!

[PwrWgnDrvr]

After all of the above and its dry, blow air thru it and most of the last debris will come out.