Walneck's Classic Cycle Trader - February 2008 - (Page 41)

SPECIAL FEATURE STORIES Once the tank is lightly pressurized, we need to make the air leaks visible. Some guys like to place the tank into a vat of water, but an old plumbers trick, using a 50-50 mix of detergent and water, is a very easy way to test. Simply pass the mixture over the tank with a paintbrush and look for bubbles. Carefully test all welded seams and then the entire surface of the tank. Even the tiniest of pinhole leaks will be easy to spot as soap bubbles will become quickly apparent. Mark each place where leaks are found. If the tank isn’t completely bare already, the leak area at least will have to be stripped to bare metal. Next we want to more precisely locate the leak. Here a magnifying glass can be most helpful while a tiny artist’s brush is employed to again introduce our soap and water mixture. Some pinholes are so tiny they are almost invisible even magnified, but the pressure bubbles will reveal these minute but troublesome critters. Once the holes are precisely located, we need to mend them, and there are numerous ways to do it. Welding is the strongest, but the hole can also be brazed or soldered too. A super easy low buck alternative commonly employed is epoxy, and while this should be avoided if other options are available, I’ve seen epoxy patches that are 10 years old and still going strong, so don’t discount the practice outright. After hole plugging, it’s time to pressure check again around each repair. If all’s well, it’s time to coat the tank, and any tank that has enough rust in it to cause a leak needs to be coated. First of all, there’s a lot of talk about coating failures, but 999 times out of a 1,000 that failure isn’t in the coating, it was in a poor job of rust removal. Not only do you have to remove loose rust, the remaining surface must be treated to convert the rust into a proper surface for the coating to adhere to. The rust can be converted through electrolysis, chemically with a neutralizing solution, or through both processes. No matter what, one must kill the rust or expect coating failure and another leak sooner or later. Of course, a tank can be coated when the paint’s still good, but one has to be extremely careful as it’s all too easy to foul up a paint job during the coating process. TIP OF THE MONTH ? Dang! This is what a pinhole leak looks like under pressure. Bucket blaster is a simple tool to strip paint and will be used to reveal bare metal around leak area. It’s even better to strip the tank completely before testing. Magnifying glass is useful to detect tiny holes and cracks. OK, now we can attend to the outer surface of the tank. Frequently, it’s highly advisable to let a pro handle the job, but no matter what course is taken, one can generally expect the inside of the tank to last as long as the paint job, meaning many years of trouble free service. WALNECKS.COM While it’s old school to use acetylene welding to fix a tank considering modern options, it’s a permanent fix if you know what you’re doing. If you don’t, take it to a pro. Regardless, never, ever weld or heat an old tank without carefully flushing it first. This one hasn’t seen gas since Jimmy Carter was president. Another benefit of pressure testing is that a combustible like gasoline isn’t needed to detect leaks. Be advised, though, that a tank can hold water but leak gas, a much thinner fluid. I WALNECK’S CLASSIC CYCLE TRADER® I FEBRUARY 2008 41 http://WALNECKS.COM

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Walneck's Classic Cycle Trader - February 2008

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