Abstract: A cooling manifold for large diesel engine systems, disposed between a lubrication oil cooler and the engine system coolant pumps. The manifold system provides an increased coolant flow area at the oil cooler outlet housing, with associated improvement in both the total coolant flow rate and the distribution of that flow in the oil cooler heat exchange tubes. The increased flow is provided by additional inlet ports, which also enhances the flow distribution. High velocity flow tubes direct a localized stream of high velocity coolant, obtained directly from the discharge of the engine coolant pumps via a recirculation line, to assure proper Net Positive Suction Head and prevent vortex void formation in the coolant pump suction during peak operating conditions. The manifold can be retrofitted on existing diesel engines, or installed in the engine system during manufacture.