90 NA is constantly running hot. I'd like to replace the thermostat but don't have the manual - can anyone tell me where the thermostat is located?

 

I just had the thermostat replaced in my 1993 300ZX. To narrow the search, it is by the timing belt and is one of the recommended parts to be replaced when you change the timing belt. It is hard to get to. Believe me! I would recommend taking it to the dealership as I had a hard time replacing mine.

 

The thermostat is on the front of the motor, you will have to take out your radiator to get to it though. follow the return hose(return hose is the top radiator hose) and follow it to the motor you will have to take off 2 or 3 bolts off of a piece of hard tubing and it will be right there

make sure that you clean both surfaces very well, use grinder to polish the "hard hose" and the side that is on the head or it might leak
hope this helps ya

 

instead of spending all that money for the dealership to do it, buy a service manual, and do it yourself. you can also put an upgraded pulley while your at it. it's not hard to do. i did mine and had no problems at all. just take your time. you have to replace the timing belt, auto tensioner, thermostat