by Kevin Johnston
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When you accidentally get a hole in the crankcase, your first reaction may be that the engine is ruined. The oil will leak and the engine will not run. If the crankcase is made of cast aluminum, you should be aware that you cannot weld it, because aluminum melts at lower temperatures than other metals. However, you can repair a hole or crack in an aluminum crankcase. Using some special materials and techniques, you can fix your crankcase and make it airtight, or better yet, oil-tight, so your engine can run safely.
Use a degreaser and wire brush to remove grease and dirt from the crankcase. Apply degreaser to both the inside and outside of the crankcase. It comes as a thick liquid that is poured out and spread with a cloth. Scrub all of the surfaces that you’ve applied the degreaser to. Pay particular attention to areas where you will apply heat while repairing the crankcase. Rub the degreaser with a clean cloth and rinse the crankcase well with soap and water.
Cut a piece of scrap aluminum to cover the hole. Do this by using “C” clamps to attach an aluminum sheet to a work table. Use a circular saw with a carbide blade to cut the aluminum so that you end up with a rectangle that covers the hole in the crankcase and extends at least 1 inch beyond the hole on all sides. Rub a candle on the saw blade to help lubricate it, but don’t melt the wax. The heat from sawing will melt it during the cut, lubricating the blade.
Heat the crankcase and the scrap aluminum patch. Use a propane torch to heat the crankcase and scrap aluminum where the scrap touches the edges of the hole in the crankcase. Aluminum solder melts at a lower temperature than aluminum, so do not apply the propane flame directly to the solder as it will melt too quickly. Instead, heat the metal and then touch the solder to the metal where the patch and crankcase meet and form a seam. The solder will melt and enter the seam.
Solder the inside of the patch. Apply aluminum solder to the inside of the crankcase where it has been patched. Place the solder along the seam formed by the edges of the hole and the patch.
Apply liquid sealer. Auto repair sealant comes in a tube that can be applied to metal parts to stop leaks. Although it is often called a liquid, it comes in the form of a paste. After the solder and metal have cooled to room temperature, apply sealant to the inner seam by squeezing the tube while running the tip along the seam to be sealed. It will form a tight seal to the metal seams in your crankcase repair job.
Put water in the crankcase and let it sit overnight. Check for drips the next day. If you find any, apply a second coat of liquid gasket.
- Make sure the solder you use is made specifically for aluminum.
- Automotive repair sealant that is suitable for engine repair is marketed under the brand names Liquid Gasket, Loctite, Permatex, and Durafix.
Articles will need
- Wire brush
- circular saw
- Carbide blade
- Clamps “C”
- Wax candles
- Propane torch
- Aluminum welding
- Joint sealant for car repair