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Old 01-28-2013, 12:27 AM
green hornet green hornet is offline
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1996 Truck
Join Date: Oct 2010
Posts: 4
Default cooling system does not warm up

The cooling system in my 96 nissan 4cyl. pickup never warms up. Temp guage stays at bottom. Figuring a stuck open thermostat, I changed it for a used one that tested good by itself in a hot water test. When I drove it the first time after the replacement, the temp went to the top within 10 minutes of driving (to work). Parked it, came back a few hours later and started the engine while eating lunch. After about 15 to 20 minutes of idling, the temp reach a little less than half the guage (about 30 degrees downward from horizontal) turned off engine to return to work. 3-4 hours later I drove about 10 - 15 minutes with NO movement of the guage and no heat! It's now acting the same way it did before changing the thermostat. I tested the thermostat which I took out (in a container of heated water) and it also tested ok. Unlike the reported cases of air in the system, my temp guage does not go up. What can cause a thermostat to stick open even when it tests ok? Is it possible that I have installed the thermostat incorrectly (backwards). I installed the thermostat with the 'stem' end, the part with the springs, toward the engine (away from the connector that connects to the hose).
Could I have two thermostats that test ok, but don't work when installed? In the case when the thermostat was first installed, it appeared to be stuck shut, then opened up then stuck open, never to return to closed. What am I missing? I don't want to replace the thermostat again if it is not the problem. I don't believe in diagnosing problems by replacing parts until the problem 'goes away' without knowing why. Help, its cold and I and my engine don't like it.

Last edited by green hornet; 01-28-2013 at 12:30 AM. Reason: spelling
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