A brick manufacturing yard reported that a Linde H25D forklift (Cummins QSB4.5 engine) emitted thick, sweet-smelling white smoke from the exhaust, especially under load. The coolant reservoir was consistently dropping, requiring a top-up of 2 liters per shift. The engine oil level and condition were completely normal, ruling out an internal cylinder leak or blown head gasket.
The technician first performed a cylinder leak-down test, which showed 100% sealing across all cylinders. He then performed a cooling system pressure test. When he pumped the radiator cap tester to 15 psi, the pressure immediately bled down to zero, but no external leaks were visible on the ground or hoses.
He removed the intake manifold and intercooler piping. He noticed the inside of the rubber intake hose was wet with a green fluid-the engine coolant. This forklift uses an "Air-to-Air Aftercooler" (intercooler) that is liquid-cooled by the engine's coolant circuit to chill the turbocharged intake air. He pressurized the coolant system again and watched the aftercooler core. A stream of coolant was spraying out of a pinhole in the aluminum core, directly into the intake air stream.
Because the turbocharger pressurizes the intake manifold to 2.5 bar, the engine was literally inhaling atomized coolant with every intake stroke. This water vapor passed through the combustion chamber unburnt, exiting the exhaust as thick white steam (the sweet smell was the ethylene glycol). Because it vaporized completely, it never condensed into the crankcase oil, which is why the oil level remained normal. The constant coolant pressure loss was the fluid being burned off through the exhaust.
The repair involved removing the aftercooler assembly and replacing the internal core (the aluminum had suffered pinhole corrosion from poor coolant maintenance over the years). The intake manifold and cylinder head ports were cleaned of coolant residue. The cooling system was flushed, refilled with fresh OAT (Organic Acid Technology) coolant, and bled. After reassembly, the white smoke disappeared entirely, and the coolant level remained stable under full load.
