running hot 280zx 83'
 

my 83' 280zx na is running about 2/3's of the was up my temp gauge??? why?

Mebbe there's no coolant in the radiator... :D

Coolant is full goes up to 3/4 s then back down to half

The gauge can be faulty or off. Get the FSM and make sure your temp sensor is reading correctly. If it goes to 3/4 then back down to half is that your thermostat opening?

Infrared thermometer will tell you right away what's going on. Measure temp at thermostat housing, and again at the bottom radiator outlet. Should see a 20* to 30*F drop.

I would personally just pick up a new thermostat. It doesn't take too long for those to go bad.

Marc the IR thermometer gave me a reading of 245 degrees fainthearted in the general vicinity of the thermostat housing. Thoughts? also is this on par with the gauge reading of 2/3's to 3/4's. the car was raised to that temperature at an idle, but according to my gauge it is also the same temp as when im driving.

thanks for all the help

245*F is hella-nuts-hot! You sure you weren't getting a reading from the exhaust manifold???

It shouldn't be any hotter than the thermostat rating (usually 170* to 190*). Time for a complete coolant flush, replace the thermostat, and yank the radiator and do a full flush too.

Pay attention to what the coolant looks like when you drain it.

I have the same problem its on 3/4 of the gauge. No more no less unless I'm on the freeway. Update on the fix?

Like I said up above get the FSM and measure it. The meter will tell you if it's the gauge or the sender or something in the harness. Starting to sound like the gauge from your other thread...