Volvo: coolant in radiator?, heater control valve, heater core

Question
I have a 1980 240 wagon.  When I drive it (and I don't at all right now), after about 5 minutes, a big poof of mist comes out the vent on the passenger side, coating the windows with fog.  My friend told me it was a hose leaking coolant into the radiator and that fixing it would cost something like 1000 dollars--but that if I routed the hose so it never went into the radiator (or something like that--the effect would be that I wouldn't have heat for the car), it would fix the problem.  I've basically been putting off doing anything about it and not driving.  I need advice.

Answer
Dan,
You mean you have a leak in the heater core or the heater control valve. The heater core is the more costly one to replace. If the valve is leaking or a hose to it that is easier. Yes if you make a bypass under the hood so no coolant goes inside the car to the valve or core you have temporally stopped the leak.