Cylinder Head Inspection
Cylinder heads must be cleaned before any crack detection can be done. Cast iron heads are cleaned 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.
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, probes etc., while fine magnetic particles are applied to the surface. A flux is created in any flaw or crack in the head, and there the fine particles will gather, showing any cracks missed during a visual inspection.
Aluminum heads are checked using a dye that penetrates into any cracks in the cylinder head. The head surface is cleaned and the dye is sprayed on and left for about 5 minutes. The surface is then wiped with clean shop rags and a developer is applied. Any cracks will 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 30 psi. or 3 times coolant system pressure is applied. Any cracks will appear as tiny bubbles in the water. Use a feeler gauge and a straight edge to check for warpage. Cylinder heads will bow in the middle when overheated. Always check manufacturer’s specifications for allowable clearances.