I just bought a 90 240 and the windows continue to fog and smoke is coming out of the vents occasionally. Anyone have any ideas. Thanks

 

Smoke or steam? Smoke is bad, steam under some conditions, (humid, A/C on) is normal.
Windows fogging is normal too--does your window defogger work? Doubt it's smoke...
All this may be due to a leaking heater core. Do you smell antifreeze inside the car? Do you have an unexplained antifreeze loss?

 

I think it is a heater core, I have the smell and it's steam. No leaking yet. What would be the best course of action? Should I pull the dash and replace? Everything else on the car is perfect so it's a real bummer.

 

Well, heater core replacement then... Or bypassing it, not having heat/defrost, probably not an option outside an emergency...
If the car's nice, replace that core!

 

if you can't replace it ASAP, disconnect the heater hoses between the engine and the firewall and loop them to each other with a short stub (which is the bypass lev mentions).

yes, replacing the heater core on a 240 is a pain, the whole dashboard has to come out. easiest to remove the front seats, gives you more room to work. work slowly, carefully, take lots of pictures or draw diagrams of how things are connected, where stuff goes, as no 2 240's are quite the same inside. while you're in there, you might just replace the heater fan motor too, those go with age and it will be lot easier to do it all at once.

 

Thanks everyone for the good advice. Will let you know how it goes.