Steps for Repairing a Cracked Exhaust Manifold

When you have cracked exhaust manifold, it might be possible to repair it rather than spend money on a new one. Taking it to a repair shop could cost you quite a considerable amount of money for labor and parts, so look at ways that you might be able to do the project yourself. Most exhaust manifolds are made from cast iron, so there are limited ways to mend such items.

Step 1 – Assessing the Damage

If the crack in the manifold is a narrow crack, as opposed to a large enough crack that you can get a finer inside it, it may be possible that you can solder it. First, remove the cracked manifold by removing the holding bolts from that section. Normally, depending on the make and model of your vehicle there will be either 2 or 3 holding bolts. Take the damaged manifold off. These repairs can only be undertaken if the crack in the exhaust manifold is not too large.

Step 2 – Preparing the Crack

Scrape off any older and worn down gasket parts and clean the surface. Bevel the crack edges to no more than 1/16 of an inch, but make sure to use a clean lint free cloth to remove any iron filings from the inside of the manifold before you replace it back in the vehicle.

Step 3 – Removing Excess Filings

Once you have cleaned any damaged edges and removed the excess irons filings and dust, take the manifold to a worktop.

Step 4 – Using the Torch

If you have never used a welding torch or solder iron before, do not attempt to make this repair. Set the Oxy-acetylene torch to its lowest level of heat and take the silver solder. Place the tip of the silver solder against the crack of the damaged exhaust manifold. Use a size 1 tip solder and place the torch very near to the solder to melt it onto and into the cracked exhaust manifold. Hold the torch evenly and use gentle strokes over the area so that you do not burn too much heat into one spot.

Step 5 - Soldering

Continue to run the solder into the crack of the exhaust manifold until you have filled the crack completely. Use a compound like JB Weld to fill any tiny holes left over. The solder solution will have a semi-permanent lifespan, but do be aware that it is strongly advised that you replace the manifold with a new or replacement part. Never cool iron artificially. Once the exhaust manifold has been finished, let the iron cool down naturally. Do not put it in cold water. The properties of cast iron are different to those of other metals and it will crack irreparably if you do this.

Step 6 – Check for Obstructions

Once you have completed filling in the crack of the exhaust manifold check the underside or inside and make sure there are no holes or obstructions. Hopefully, having completed this, your exhaust manifold will have a solid finish and be secure enough to replace onto yours.