1999 Volvo Penta "WT" Models Workshop Manual, Page 350Get this manual
Cylinder Block Water PassagesCorrosion, slag, blocked passages, or leaking core plugs
Cylinder HeadCorrosion, slag, blocked passages or leaking gasketsimproperly installed; corrosion, sand, or slag in manifold and elbows; hoses collapsed, burned through, or leaking
l Exhaust Manifold, Elbows, Gaskets, and HosesGaskets