I wasn't sure if this is an engine or electrical problem so I'll start here. I have a 82 280zx 2+2. runs and drives great, no problems there. There is only one problem that I have been having lately. With motor running, I have never seen my water temperature gauge go anywhere near the middle where it should be. It only goes up a little bit from the 120 mark. The gauge seems to be accurate, the motor never actually get hot, it only get somewhat warm. My heater just barely gets warm, even after car has been running for hours. Any thoughts on this? I was thinking maybe the thermostat is stuck open or something, this car did sit for a couple of years before I got it. I will post a pic later of water temp gauge with car running so you guys can see where it's at.

Edited January 9, 201213 yr by p_trice

Hello p_trice,

Did it just start doing this, or did you just buy the car? If you just bought it there may be a very cold thermostat in it, or stuck open as you said, or no thermostat at all.

Thermostat would be where I would start, as long as your radiator is full (assuming you checked that already). Cheap and easy to change out yourself.

Bryce

If it is a problem you have been experiencing lately like your post reads then I would assume the thermostat is stuck open. remove the thermostat outlet and check it out. Let us know what you find.

Bob

Before you take apart the thermostat housing (though a stuck open thermostat sounds likely), use a candy thermometer to verify. Idle your car with the radiator cap off (that is to say don't drive around). Let it come up to temperature, and measure with the thermometer. If it matches the gauge, as Bob suggests, look at your thermostat. Your Nissan dealer probably still can get the correct thermostat. It's worth the money to go genuine Nissan with that.

I have had the car for about 5 months. When I got it, it didn't even run or drive. It has been doing this since I got it running. It has only been running and driving for about 2 months.

You could try lightly tapping on the thermo housing, might get lucky and un-stick the thermostat. But plan on changing because this is a classic symptom of a stuck thermostat

As SteveJ said above, measure before you do anything. A candy or meat themometer works fine. Warm the car up with the radiator cap off, then measure water temp. If it's around 160 F, to 180 F, it's good and your gauge is off.

I ended up taking apart the thermostat. It did not appear to be stuck when I took it apart. I tested the thermostat to see if it would open, It opened at 180F just like it should. So now what? it appears I have a different problem on my hands. Either my temperature gauge is off or something else is going on. I was thinking maybe the thermostatic fan clutch was not working right. Maybe the fan is spinning to much when the car is cold. I have seen it happen on different cars. I tried spinning my fan by hand and it is kind of hard to spin. Shouldn't it spin fairly easy? I am going to get new thermostat and gasket tomorrow, then go from there. I don't think my temperature gauge is wrong, I have seen it move up some, but not where it should be. After driving all over, motor wouldn't even be hot enough to burn me, just very warm. I could touch the engine block with my bare hands. Any thoughts?

Go to Xenons130.com and find the FSM from the 82. It should tell you how the fan is supposed to behave. By the way, did you actually measure the water temperature at the radiator when the car is warm?

No, I did not measure water temp with car running, as I already had the motor somewhat taken apart at the time. I plan to measure temp tomorrow after I get new thermostat, and get motor all back together.

after closer inspection, I realized that the old thermostat didn't close all the way and the seal was broken and cracked in spots. Could the problem have been coolant leaking past thermostat when car was cold, which in turn would never let it get up to full temp? I put a new thermostat in today. I saw the temp gauge rise higher then ever before. My heater was actually blowing hot air, not just warm. I did temp test with thermometer, my temp gauge is spot on. I am so relieved, I was starting to think I had much worse problems on my hands.

Edited January 12, 201213 yr by p_trice

Didn't you answer your own question?

When the thermostat didn't close, the coolant system lacks the restriction to flow that it needs to get the engine to the proper operating temperature. If you look at common trouble shooting guides for cooling systems, you should find a description that pretty much matches what you experienced. Here is an example.