Cylinder Head Distortion

WARNING: This page is about a different car, the 2006 Lincoln Navigator and 2006 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Make sure all cylinder head surfaces are clear of any gasket material, RTV, oil and coolant. The cylinder head surface must be clean and dry before running a flatness check.
Use a straightedge that is calibrated by the manufacturer to be flat with 0.0002 in (0.005 mm) per running foot length. For example, if the straightedge is 24 inches (61 cm) long, the machined edge must be flat with 0.0004 in (0.010 mm) from end to end.

Fig 1: Inspecting Cylinder Head For Flatness

Courtesy of FORD MOTOR CO.

Using a straightedge and a feeler gauge, inspect the cylinder head for flatness in the sequence shown in Fig 1. If the cylinder head is distorted, install a new cylinder head.