Nissan Repair: 240sx overheating, temperature gauge, headgasket

Question
A week or so ago I noticed that it was taking longer and longer for the heater in my 240sx to get get to blowing out hot air.  Then, when I last drove my car, I noticed that the temperature gauge had maxxed out while driving, and when I was pulling over to stop, the heater finally started warming up a bit.  So I turned around and drove home, and the car started cooling a bit, but the heater never got to full heating temperature, and the car never got back down to normal operating temperature.  Since then, I have replaced both my thermostat and water pump.  When I started up the car again after that, the car again began to overheat, and the heater never did start putting out any hot air.  Any idea what the problem is, and how to fix it?

Answer
Devin,

I have done a few of these.  First, check to see if the headgasket has not blown as it probably has.  And, check to see if the converter is plugged as that is probably what took out the headgasket.  The headgasket can be checked by using a kit from the parts store that detects exhaust gas in the coolant.  If this is the case replace the headgasket and the converter.