need help

[calipowerstroke]

this past weekend my friend drove his car off of a clif trying to impress his gf with his driveing skills well i helpd him recover the car off of the side of the mountain well i left the truck idleing while we were setting up the recovery straps and what not adn i noticed when i went to hit the gas to ppull him back up the cliff my truck started dumping white smoke so i turned it off after we get the car back on the road and get it loaded on the trailer i turn it back on and it runs fine didnt do it again then the other day after letting it idle for 10 minutes at the liquor store i went to leave and it did it again seems to only be ater it sits and idles for 10+ minutes after its warmed up dosent do it in the morning. i pulled the intake and checked the turbo their was slight oil residue on the intake walls of the turbo but no shaft play im new to diesels its never over heated so i know its not a blown head gasket but dose anyone have anyideas of what it might be the truck has 170,000 miles any help is greatly appriciated