Please help Losing water freightliner with cat 3306 fld 112

Hello , first of all thanks for taking time to help out with your collective knowledge , have a dump truck original freightliner fld 112 , year 1995 with a cat 3306 , 8ll tranny and 456 rears , we bought the truck about 4 months ago its been doing great however we are loosing a lot of water on a weeks time about 4 to 5 gallons of water ( that's a lot of water ) facts : truck runs 300 to 400 miles a day sometime more , starts in the morning perfectly no white smoke , no engine misses hot...

Please help Losing water freightliner with cat 3306 fld 112

Please help Losing water freightliner with cat 3306 fld 112