My S13 never seems to heat up

[dareo]

Ever since cold weather hit here my S13 seems to not warm up. Temp gauge stays solid cold. Heater blows fairly warm, but not hot air and the engine generally seems warm, but the radiator is always just cold.

So i figure, the thermostat is stuck open, and buy a new one. I put that in (real nice placement on the t-stat nissan thx a lot..) But my car never warms up still. I dont think its the gauge cause my radiator is never warm itself. Gas mileage is now around 200 a tank with the MTBE or whatever they put it in it now combined with the cool engine. I used to get 250+

Is this going to be the utter destruction of my motor if i just dont care for a few months till i swap? I dont care if the motor dies just as long as it lasts till i get a swap ready.

[NISTECH]

you really need to take care when bleeding air from system during refill. if you have air trapped in the system and that air pocket is near the coolant temp sensor it will read full cold even if the car over heats and your heater will not blow hot. when the car is at what you think is operating temp try grabbing the upper and lower radiator hoses. they should be hot to the touch but you will still be able to grab them with out scalding heat. compare the 2 do they feel to be about the same heat? if they are so hot you cant even grab them without yanking your hand back for fear of being burned I would say you still have a large airpocket in the system.