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 wire brush.
Some sanding pads are too coarse for aluminum and should be avoided. We usually call these pads "Cookies" and they can damage the surface when cleaning gasket off aluminum. There are many softer brushes on the market that are excellent for this application. Always practice care when dealing with aluminum parts.The important thing is not to change the original surface. Plastic scrappers and gasket softeners work great for removing old gasket material.
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 the flaw or crack in the head and 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 and 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.
