The 3.7L V6 and 4.7L V8 in very cold climates (below freezing temperatures) moisture can collect in the Positive Crankcase Ventilation (PCV) system and freeze. This will cause various drivability problems and there are revised PCV system components to repair this concern.
Car Problem Reports
Jeep Liberty Moisture May Collect in PCV System and Freeze in Cold Climates
Jeep Liberty Problem
Exhaust & Emissions Affected: 3.7L V6
Average Mileage: 79,666 mi (73,000 mi - 90,000 mi)
Visitor, 2006 Jeep Liberty, 90,000 mi
My PCV lines froze and blew both my valve cover gaskets - twice so far. Live in alaska and temps were 25-40 below at the time. After first repair, started parking indoors at work (no garage at home) and letting engine idle for 25 minutes after running short trips to and from work (17miles) and covering hood with a blanket at night while plugged in at home.
Visitor, 2004 Jeep Liberty, 76,000 mi
moisture on the filler cap and in engine