Tech Hint

Oil Entering Intake Manifold During Start-up

This tech hint pertains to the Ford Mustang, Bronco, Econoline, and F-Series pick-ups, l994-95.

When refilling the crankcase, oil can be forced through the engine's PCV closure system into the intake manifold. This usually occurs when using an air-powered delivery system if the nozzle is directed toward the PCV closure port. Oil entering the system may be drawn into the cylinders during start-up creating hydrostatic forces on the pistons, connecting rods and crank shaft. These fluid forces can cause engine damage and a possible lock-up.

To prevent this scenario, disconnect the closure hose from the oil fill pipe and position it away from the oil sources. Cover the hose port with a shop towel to prevent oil from spilling onto the engine during oil fill. After filling the oil to the proper level, reconnect the closure hose. Caution: Take care to direct the oil control nozzle away from the closure hose port into the oil fill tube during oil fill.
(Source: Mitchell On Demand)