Nissan Repair: 300zx overheating help!, chilton book, steam cleaner

Question
I have an 87 300zx non turbo. one day it started over heating and smoke was coming through vents on the top of the dash and the floorboards.when this happens it appears i have no water flow so i add water the engine cools and stops. but i drive for 5 min on the highway overheating and smoke. i look under the car doesnt look like its leaking. my floorboard is soaked i think its the heater core but im not sure.
my question is do you think the heater core is the problem and if it is, is there a way to bypass it? i started taking the dash apart but i have old useless chilton book that shows almost no pics so im having trouble finding it. any suggestions ?

Answer
Mario,

You need to replace the heater core as it is leaking.  You could loop the hose with the engine for now.  But, the heater core needs to be replaced before winter.  Basically, get a hose the same size as the ones that go to the firewall.  Take off the hoses at the engine side and then connect the new hose to one pipe and loop it to the other pipe.  Now, clamp it down and you should be good after you fill the car with a 50/50 mix of antifreeze.  The best way to get to the heater core is a factory service manual as I cannot begin to describe the process here.  But, you already know that it is on the passenger side under the dash.  Also, get a steam cleaner and get the antifreeze off the carpets before it messes them up.  Leave the floor mat out for a couple of days to allow the carpet to dry afterwards.