Nothing is more agravating than working on a vehicle and having a bolt that you are removing or installing break off due to rust or a little too vigorous pulling on the wrench. It is doubly frustrating when the bolt that breaks does so on a heavy part that is located in a difficult area to reach. The exhaust manifold is just one such example. The exhaust manifold is located on the block of the engine where the air flow containing the carbon monoxide is expelled from the engine. There are two main methods to remove broken exhaust manifold bolts.
Allow the vehicle engine to cool off before attempting to begin this process. Put on your goggles and dust mask for safety. The success of the method depends on the reason the bolt has broken. If due to extreme rust or stripped threads on the bolt, the cold method may not work, but it is a good starting point.
Soak each bolt front and back with PB Blaster spray. It is a penetrating lubricant that works down into the threads and makes removal easier. Tap the bolt firmly, but not enough to deform it with a hammer or box wrench. If the bolt is not easier to remove within an hour, soak the bolts again with the PB Blaster. Allow them to soak for a full day or two if you are able. If you do not have PB Blaster, WD-40 is a good alternative. Do not spray a hot exhaust manifold with any kind of lubricant as it could ignite a fire.
Pull on the bolts with a stud puller and twist in a counter-clockwise direction. If the threads have been stripped, try to pull the bolt straight out. If the bolt will not budge, you will have to use the next method.
Drill a hole down the center of the bolt. Insert the bit into the hole of the bolt you just created and use the screw-back extractor to remove the bolt. These specialty tools can remove even the toughest bolts, but require a steady hand and drilling into the exact center of the bolt. Set the drill on reverse insert with the screw-back extractor attached and the bolt should come out. If it doesn't, the cold methods have not worked and you will have to use the hot methods.
Remove the manifold from the engine block. The exhaust manifold, including the bolts, is held to the engine block with studs and nuts. Remove these studs with a crescent wrench and lift the manifold off. If you cannot remove the manifold, you must use extreme caution with the hot method as it involves using an acetylene torch.
If you have steady hands and experience with a torch, you can try the following step with the exhaust manifold still attached on the engine. Do not attempt if you have no experience doing this. Make sure none of the penetrating spray is present before using a torch on this area. It takes a few hours for the spray to evaporate.
Put on the welding mask and gloves. Goggles will not protect your eyesight. To remove the exhaust manifold, depending on the model of F-150 you own and the year it was made, you may have to remove the engine head to get access to the manifold bolts. You may need an engine crane with chains to support it's weight and unbolt it from the block with ratchets or crescent wrenches.
Locate a nut that is roughly the same size as the head of the bolt. Weld that nut onto the head of the bolt and let the weld cool. Use a box wrench or ratchet that fits that nut and twist it out. Use the welding tools to secure the nut to the broken bolt head. This method can be used with the manifold removed or attached.
