Exhaust manifolds usually become the most unattractive parts in your engine bay, especially after years of use. It's very easy for an exhaust manifold to become covered with rust, soot and grease. Because exhaust manifolds are made from cast iron, certain precautions must be taken when cleaning them.
Locate the exhaust manifold on your vehicle. The exhaust manifold is located at the front of an engine on front-wheel drive models and on the side on rear-wheel drive models. V-6 or V-8 engines have two exhaust manifolds, while four-cylinders have one.
Let your engine cool off for at least 30 minutes before you begin. The exhaust manifold gets extremely hot.
Remove the bolts from the manifold heat shield. The heat shield is usually metallic or silver; most newer vehicles have them. Spray the bolts with solvent like Liquid Wrench or Rust Busters prior to removal.
Remove any vacuum hoses attached to the exhaust manifold, such as the EGR valve hose, and then remove the bolts from the exhaust manifold. Like the heat shield bolts, they are difficult to remove. Using a socket wrench with an extension will help you apply enough force. It will be very difficult to remove them without applying a solvent.
Remove the exhaust manifold from the vehicle and set it on a clean work space. Apply lacquer thinner to it and scrub it vigorously with a scrub brush. Do not attempt to clean it with water. Most manifolds are cast iron, which absorbs water. Water can ruin your exhaust manifold.
Let the manifold sit for a while and begin scrubbing again. The process of cleaning a manifold is not that difficult; it just requires elbow grease and patience. Once you are satisfied with its appearance, wipe the manifold thoroughly.
Apply a dressing or protectant to your manifold. While this is optional, it will protect it from rust in the future. See the Resources for manifold dressings.
Reinstall the manifold with a new gasket. Exhaust manifolds need to be tightened in a specific sequence to a specific torque level. Contact your local dealer or purchase a repair guide for the specifics. Reconnect the vacuum hoses once, and reattach the heat shield when you are finished.
