shoust---
I've made my fuel day tanks and cooling tanks from propane containers. Here's how *I* do it and I'm still typing with both eyes and hands....
Open the valve outside and leave it open for several days...the cool/hot cycles are important. Then pull the main valve. It's easier to do if you break or cut the guard off first.
Squirt compressed air in the valve hole for about twenty minutes...do ALL this outside. I thread a piece of plastic tubing on the air chuck so the air works from the back of the tank outward, but it probably doesn't make any difference.
Once the tank is flushed with air I've cut, drilled, sawed, welded, brazed and torch-cut on them without harm. They still SMELL dangerous, though!!
All of them can use a complete washing with dilute phosphoric acid (Naval Jelley) and warm water to remove the rust and crust that forms in them.
WATCH for leaks in the future if they're attached to an engine. They aren't too heavy duty. Brazing is better than welding because they have some carbon that makes them subject to stress cracks from vibration. I mounted mine with rubber shock absorbers but still developed stress cracks and seeps along properly pre-heated welds with stretchy stainless steel filler rod.
The easiest cooling tank or fuel tank can be made with three pieces of angle iron brazed to the tank so that it's a verticle tank with three legs of what ever length you want as long as they're braced or attached to a base to keep the top-heavy problem solved.
Invest in a hole saw the proper size and braze bronze pipe sections or fittings in the tank for taps or drains. A forest green tank with bronze fittings is plumb PRETTY!!
The next time I'm in town with a trailer I'll call on my buddy at the propane place. I need a couple of bigger ones for projects. i think I'll extend the 'flush' time to match the larger volume.
Re: Mufflers-- I ran the exhaust pipe into the top of a section of concrete sewer pipe through an old spare tire. It's pretty well sealed and kills the noise without having to dig a hole.
