2.5 - Exhaust Manifold ( Paul Stow,  December 1, 2001 )

cracked exhaust manifold

Undo the six bolts securing the heatshield and remove it. On US models, remove the EGR.

Inspect the manifold for cracks. These are usually obvious, and may also have caused a dark line of soot on the manifold and heat shield underside. They cause increased noise and can affect ECU inputs from the Oxy sensor in the downpipe. Use a dentists mirror or similar to check the underside of the manifold.

A reasonable cure may often be made with a wet solution of exhaust putty pushed into the cracks, or a heat resistant epoxy, but a long term fix requires welding or replacement. Specialist welding is required, as a simple furnace weld is likely to warp the manifold and cause more problems.

Undo the exhaust downpipe to manifold bolts and lower the exhaust. This will be much easier if the bolts have been soaked in penetrating oil for a few hours beforehand.

Undo the manifold nuts and gently rock the manifold to release it.

Clean the manifold and head surfaces thoroughly before replacing the manifold, and use a new gasket. Otherwise, refitting is the reversal of removal.

If removing the lambda sensors from the downpipes, take care to mark them and reinstall each in it's original location. If they are reversed, the ECU cannot understandwhat is happening in the engine and will set a check engine error code.