Cylinder Head Inspection
Clean the cylinder head before inspecting for cracks and damage. Remove old gasket material with spray-on gasket remover and a plastic scraper. Clean cast iron heads in a hot tank with a caustic solution. Aluminum heads are more delicate and are best cleaned with an appropriate degreaser and a small brush.
Cylinder heads tend to bow in the middle when overheated. Use a feeler gauge and a straight edge to check for warpage. Always check the manufacturer’s specifications for allowable clearances.
Cylinder Head Crack Detection
Iron cylinder heads: Magnetic particle inspection or Magnafluxing® is the process used with ferrous or iron cylinder heads. A magnetic field is created using a permanent magnet, cables, or probes. At the same time, fine magnetic particles are applied to the surface. A flux is created in any flaws or cracks in the head; the fine particles gather, revealing any cracks missed during a visual inspection.
Aluminum heads are checked using a dye that penetrates inside any cracks in the cylinder head. Clean the heads surface, and then spray the dye on and let it sit for about 5 minutes. Wipe the surface with clean shop rags and apply the developer. Any cracks show up as red lines.
Pressure testing is done in a tank of water. All ports and passages are covered with plates and inserts. About 3 times coolant system pressure (30 psi.) is applied. Any cracks appear as tiny bubbles in the water.