Some 2006-2009 Mercury Mariner Hybrid vehicles may exhibit a leak from the power transfer unit (PTU) vent tube bolt. This may be misdiagnosed as a PTU link shaft seal leak.
Verify and tighten the PTU vent tube bolt before replacing parts. Remove the PTU fill plug and check fluid level per workshop manual section 308-07B. The fluid level must be even with the bottom of the filler hole with the vehicle on a flat surface.
If the PTU vent tube bolt is leaking, clean bolt contact surfaces and torque the bolt to 120 in.-lbs. If the PTU vent tube bolt is not leaking, continue with normal diagnosis. NOTE: The vent tube bolt does not require a washer.