Okay, DDS60 (1996 model) in FLD120 with 702k. First driver said it lost about 9 gallon all together on about a 2000 mile run in the southeast. Changed radiator cap - old one looked bad - and now driver says truck is loosing about 1-2 gallon over about 2500 miles or so. We took it into the local Freightliner shop and they "couldn't see a problem" - they let the truck idle for a while and no leaking, put the overflow hose in a jug and drove it around for a 30min test run and no water leaked into the jug. The tech said he felt for sure the head gasket was not an issue and mentioned that the valve for the bunk heat could have been "sticking" and pumping some air into the coolant system and pushing some water out - but "must have fixed itself?" cause he couldn't reproduce the issue.
Driver says the truck never gets over about 180-190, but is still leaking water. Any ideas where to look next? I am also thinking of having a more capable shop / tech take a look at it as well.
Just as a side note incase it is relavent - recent oil samples showed 1.5 to 2% fuel in oil, had local Freightliner shop check injectors with dye test and found nothing - chalked it up to excessive idle. Haven't had the next oil sample done yet.