vmac2

Hi there. Has your vehicle been updated with the new cooling system package that Mack has come out with? They updated the thermostat housing along with the thermostats and coolant piping. The thermostats are 180 and 185 degf. They also went with a one peice 16lbs coolant revovery bottle made of aluminium. Back in 2004 they had alot of issues with the plastic then steel tanks leaking. Also you may have a water pump causing this issue. The static seal behind the weep hole may be drawing in air. Take off the water pump and put it inside a pail of water so its completely submerged. Get a rubber tipped blower and blow a small amount of air into the weep hole. If you see air bubbles in the pail of water, then you have a bad water pump. An internal crack in the egr cooler can cause the coolant to be presurized. Also if your engine has overheated for any reason there lies a possibility that you may have damaged the egr cooler. As long as the egr cooler has good coolant flow the cooler should be o/k. A cooler blocked with soot should only give you egr fault codes. Hopefully a simple rad cap may be your problem. Regards vmac2