DIY Engine Repair Part 1 - Salvaging Engine Components with 2-Part Epoxy

As a followup to my previous post, I decided to dive a little deeper and give a full overview of the process behind repairing engine components with epoxy.

Either your best friend or worst nightmare, depending on the mechanical aptitude of the previous owner.

2-part epoxies, such as MarineTex and J-B Weld, are commonly used to repair damaged engine cases when a weld repair is not economical or practical. I will use the subject of my last post, smoothing a rough gasket surface, as the example. The first step is to fully (FULLY!) clean the surface that will be epoxied. Any oils or paint left behind will cause a bonding failure, and sooner or later the entire repair will fall off and you will be back to square one.

Fully cleaned with acetone and a stiff brush.

This step is especially important when using the epoxy to repair a crack that oil is seeping though. In addition to cleaning the surface, you must try to clean the oil out of the crack itself, so that any oily residue in the crack does not prevent an internal patch of epoxy from fully setting. I usually do this with a can of carb cleaner, an aiming straw to inject solvent into the crack, and a comprehensive list of creative swear words for when the spray ricochets back and hits me square in the eye.

Mixing the Epoxy

 Epoxy dries better when everything is warm, so either keep a heater near the parts you are working on, or move everything indoors. Once everything is up to temperature, mix the epoxy on a clean dry surface with a wooden paddle. I prefer to use MarineTex epoxy.

In this case, I used the epoxy to build up a rough surface so that I could smooth it down. For the first step, I spread a thick layer onto the metal, on the area to be sanded.

Next, I used a razor to scrape off the excess, only leaving behind a small amount in the cracks. This is just the first application to fill in the worst cracks, so it doesn't have to be perfect. You should use multiple small applications of epoxy to build up the surface, because one thick layer may not set correctly or harden thoroughly.

I allowed the epoxy to dry for 24 hours next to a heat source, and then mixed a second batch.

The second layer of epoxy was applied and smoothed with the razor, but not scraped flat like before. I once again allowed it to dry for 24 hours, and then  used a sanding block and 600 grit sandpaper to smooth the surface down.

In progress

Finished! All the missing metal has been replaced with epoxy and sanded smooth.