Hopefully it is one of the freeze plugs in front of the engine that is leaking, but if it is the head,one of the causes of cracking in cast iron heads is stress created when the valve seats are induction hardened. The concentrated heating process that hardens the valve seats also creates residual stresses in the head that may cause it to crack later - even if the engine has never overheated. The cracks typically form where stresses are highest, which is often between the valve seats.
External coolant leaks due to cracks are not as common because the outside of the head runs considerably cooler than the combustion chamber and exhaust port surfaces. Even so, cracks sometimes form in these areas that leak coolant.
Check for leaking freeze plugg first, you may be lucky.
Oct 17, 2009 at 5:09 PM
