Fuel Tank Liner

By: Steve “Brewdude” Garn – www.brewracingframes.com

Originally Published In The August 2016 Issue Of Cycle Source Magazine


Over the years I have seen many gas tanks. The inside of these tanks have varied from being in great condition, or in need of much work. The worst of these are the tanks that someone has applied a tank liner coating to that has failed; over time they crack or can flake off. In these cases, most blame the tank liner brand, but in all reality it was actually caused by improper prep or improper application of the tank liner. In this tank the liner has been flaking off.


When I flushed the tank out with some fresh gas this is what came out.


The first thing to do is add some water with a degreaser. Some add nuts and bolts to slush around inside to help loosen the old liner, but as you can see I just use some gravel. Be sure to remove the fuel petcock and plug up the openings. If you leave in the petcock, it can damage the internal fuel filter it has. What works best for a plug is an old petcock. After slushing the tank around in all directions, drain it out. As you can see, this tank was so dirty that you can’t even see the tank liner pieces that came out with the flush.


Repeat this degreaser gravel mixture until it comes out pretty clean. Don’t use tape as a plug for the next procedure, acetone will melt any tape over the petcock opening. Fill the tank with acetone. The acetone will soften/dissolve the remaining old tank liner still left in the tank. The acetone for this circumstance took an overnight soak before all the old liner came out. Be sure not to let the acetone get on the outside painted surface of your tank, or your paint finish may become damaged. Repeat again the water/degreaser mixture with gravel to get all the old liner debris out. Repeat until it comes out clear, and then flush with water. Drain all the water out the best that you can. Use a metal prep that will leave a zinc phosphate coating. I use the POR-15 Prep & Ready; this will neutralize any remaining rust in the tank. Follow the directions on their product! It is easy, fast and does a great job. Don’t let the Prep & Ready dry or you will get a light film on the tanks inside. Be sure to flush out well with water, and don’t leave any residue of the Prep & Ready inside the tank. Add a little acetone and slush around. This will remove all the moisture still in the tank.


Remove the old petcock and mask off opening. This way you can be sure when liner application is done that the opening for the petcock is fully open.


Mask off the outside of your tank with tape so when you pour liner in any spillage will not hit your tank’s paint. Waxing before you mask off will ease in removing the tape after the liner application is done.


For this tank I will be using the Caswell 2-part epoxy liner. Over many years, I have used many brands of tank liner and I have never had a failure with any of them. No matter what brand you use, be sure to follow their instructions exactly! Some liners, if applied to thick, will crack over time, and some you can even apply a second coat. Just be sure to follow what their instructions say. If you have a question, call the company that manufactures it. After the liner is poured into the tank, rotate it to be sure the entire inside of the tank is coated.


Pour the liner out and let dry per the tank liner instructions. The Caswell dries as a clear liner. It comes out slick and shiny and ethanol or other additives do not harm it.


Take your time, follow the instructions on the product you buy, and this will be a long lasting liner for the interior of your gasoline tank.

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