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Discussion Starter #1
I just finished a complete rebuild on a D16Z6 which included a new oem water pump ,radiator, fan, thermoswitch, temperature sensor, ect sensor and thermostat. While driving, the temp gauge is reading between the quarter to one third mark. When sitting at idle the gauge slowly climbs and the fan does not turn on. I have let it climb to the three quarter mark and no fan. I jumpered the thermoswitch and the fan turned on, so I replaced the new thermoswitch with another and still no fan. I tested the first switch in hot water and continuity was fine. I unplugged the connector from the current switch and plugged in the original switch. I put a lighter under the switch and the fan turned on which tells me there was nothing wrong with the first switch. If I let the temp gauge climb over half-way and then jumper the thermoswitch to kick on the fan, the temperature goes back down. To me this means that thermostat is open, coolant is circulating and the water pump is working. At this point I am lost as to why the fan does not come on and am looking for ideas on what else to try. Thanks.
 

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Sounds like you need to bleed the cooling system.


Jack up the front of the car as high as you possibly can, remove the radiator cap, and let it idle til it is hot. Once it is hot and climbing on the gauge past the 1/2 mark, simply shut the car down and let it cool off. It will get hotter once the engine is off for a short time, since the water pump is no longer pumping and all that heat has to go somewhere.
 

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Discussion Starter #4
When I tested continuity of the thermoswitch the water temperature was between 190 and 200 when it closed.
I'll try and bleed the cooling system over the weekend. Thanks
 

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Bleed it as indicated. I use a steep hill instead of a jack and in Tacoma its easy to find hills that are close to 45 degrees. The higher you can get the front the better. In Ellensburg I pull it head in, up onto the sidewalk over the curb, and then jack it from the sidewalk but if youre lowered that might not be an option.
 

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Discussion Starter #7
Problem Resolved - found a video where someone had the same issue after installing a higher performing radiator. They installed an actual temperature gauge and found the temperature was lower than what the stock gauge was reading. I installed a temperature gauge and at 195 the fan kicked on. The stock gauge was showing past the 3/4 mark. Before installing the gauge I would not let the stock gauge climb that high.
 
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