On my 93 the thermostat is behind the water pump. If you remove the waterpump you will see the thermostat.
To install a thermostat on a 1987 Nissan 300ZX, remove the two nuts and one bolt on the lower water neck. Slip off the old thermostat and use a gasket sealant to secure the new thermostat.
In the thermostat housing on the front of the engine were the radiator hose attaches
water pump
When changing the thermostat on a Nissan 300zx first drain the coolant from the engine. Then find the lower coolant hose on the radiator. Trace the hose to the thermostat housing. Remove the housing to uncover the thermostat and replace the unit with a new thermostat.
http://www.300zx-twinturbo.com/cgi-bin/manual.cgi
You'll have to take off the water pump because that is where the thermostat is.
should eather be at the top in to engine or on bottom hose coming from engine
the main hose coming off the top of the radiator were it goes int0 the engine.
There were 3,000 Nissan 300zx convertibles made
VG30DETT is in the 90-95 Nissan 300zx. It is a v6
Low coolant? Control cable not adjusted properly Bad thermostat?
Yes it will