My upper radiator hose connector broke and I drained the system, replaced the radiator and refilled the system. It kept overflowing through the overflow tank after stopping and turning the car off but the Nissan mechanic told me the system needed to be bled or "burped". you need to park the 300zx at an extremely upwards angle with the nose up and fill it to remove the air from the system. Mine stopped doing this once I did that. HOWEVER (!) I have found that my car is CONSUMING water in one way or another and I have to top the sucker off every morning or eventually it consumes too much, and starts to overheat. I don't know if this is related but my vacuum pressure (tested at plenum where it goes to clutch booster) is rapidly oscillating. I'm not sure the cause of either one of these. I'm thinking a blown head gasket. The car runs a bit rough. At idle it occasionally drops about 100-200 rpm. I think it's called loping. It still runs but sounds poopish. Any diagnose, advice, or input is extremely welcomed.

91 300ZX TT