Crankcase Pressure Test: Purpose

WARNING: This page is about a different car, the 2008 Ford Pickup, 2008 Ford F550 Super Duty, 2008 Ford F450 Super Duty, and 2008 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The purpose of this test is to measure the crankcase pressure. Crankcase pressure is a measure of how well the cylinders are sealing.

Crankcase Pressure Test

Measure the pressure at the oil fill tube with Adapter, Crankcase Pressure Test 303-758, with the engine at 70°C (158°F) minimum.
Block the breather tube.
Measure with no load at 3,000 RPM.

Instrument	Specification	Measurement
0-60 in-H₂ O Magnehelic® gauge	Less than 10 in-H₂ O

If greater than 10 in-H₂ O, refer to ENGINE SYSTEM - GENERAL INFORMATION -- F-250-550 (SUPER DUTY PICKUPS) Component Test compression test-compression gauge check to continue diagnosis.

Fig 1: Measuring Pressure At Oil Fill Tube With Adapter, Crankcase Pressure Test 303-758, With Engine At 70°C (158°F) Minimum

Courtesy of FORD MOTOR CO.