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| Cylinder Head Inspection |
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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. The important thing is
not to change the original surface. Plastic scrappers and gasket softeners
are used to remove 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.
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