Shadetree

..My sons GC Limited 5.2 w/120K miles keeps losing coolant, but hasn't overheated..He checked last week and saw his coolant level was a couple inches below the add mark..He filled it to the full mark..Next day, same thing..He's done this for 6 days..When he checks it in the morning it 's below the add mark, with no evidence of leakage on the ground or anywhere we can see..We've checked all the hoses..no signs of water in the oil..runs great..He drives 100 mii or so per day, and seems to lose the same amount..Anyone have any idea where the coolant could be going?..

Bustedback

Out the exhaust? Inspect the radiator very closely, the tanks will split and only leak while under pressure. Rent or borrow a cooling system pressure tester, check the radiator cap, and the cooling system.

Shadetree

Thanks Bustedback..We got a loaner cooling system pressure tester from Auto Zone and found a pin hole on lowest part of radiator..driver's side...didn't even show up until under 10 lbs pressure..The kid had to take an emergency trip with no time for radiator repair so he opted to use Alumaseal...The tester showed no leak at 15 lbs so he took a 700 mi trip with no coolant loss below the add mark...except...there must have been some air pockets in the cooling system because he still added another 3 quarts over a period of 4 stops (before his first fuel stop) for coolant check before the level stayed at full mark and has stayed there...Now has 500 miles on the Alumaseal with zero coolant drop....Thanks again..