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Discussion Starter #1
Hey guys,

Been looking through threads for a while now and cant seem to get a definitive answer on my problem. I have a 97gt with a pi swap and a bunch of bolt ons..notable underdrive pulleys. Just trying to think of anything that might relate. I also have some reground pi cams which result in an idle of about 700-800 rpms.

I have been overheating at idle for a while now and cant seem to track down the reason. I have replaced the thermostat with the stock one, i replaced the radiator cap (i have the moroso overflow tank from american muscle btw) and replaced the fan with a mishimoto from american muscle as well. In November I had to replace the fan because the stock one wasnt turning on.

I have a digital temp guage that tells me how how the car is running and it will hold around 205-215 while in motion but when i stop (especially in stop and go traffic) it will go as high as 235 and probably higher if i dont start moving again or shut it off.

Could is be that i placed the fan to low on the radiator or is the radiator going bad? Its still the stocker radiator. Any help would be AWESOME! thanks!
 

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Is the fan coming on? 235 is not going to overheat the car, although it is pretty warm. Make sure the fan is kickin on and off, if not it could be a problem with the temp sensor or the relay in the ccrm.
 

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Discussion Starter #4
Yeah the fan comes on at around 210...at what temp should I start worrying...I thought it should stay around 210-215
 

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How about air in the cooling system. The 4.6 is a real PITA when it comes to bleeding the air from the system. They do make a special tool for it but I have had pretty good luck with just raising the front end while filling the cooling system. Also, I would suggest a 180 degree thermostat? I don't think I see more than 195-200 in my car at the worst of times.
 

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I would make sure the fan is working properly and switch to a cooler thermostat.
 

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Make sure your fan is blowing air in the right direction. Sometime after a swap on the fan you can have it blow the opposite way out of the box. When i put an electric fan on the falcon we had to reverse the polarities.
 

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Yeah the fan comes on at around 210...at what temp should I start worrying...I thought it should stay around 210-215
My car will get up to about 235 in the florida heat but come right back down to around 200-210. It has done that for 3 yrs. i have a mechanical temp gauge so Im not sure how accurate it is but i have never overheated.
 

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mine over heated and spun a #6 rod bearing now under rebuild
 

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i don't think anyone has mentioned to check the fan?;);)
 

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You say you have underdrive pulleys, am I the only one here that thinks it is possible that the underdrive pulley on the water pump is causing the waterpump to improperly circulate coolant? It explains why it only does it at idle.
 

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Discussion Starter #12
well i am in florida so it is pretty hot however, there is a distinct change as i slow down the car. At idle or below 35 i will get upwards of 240 on the temp guage and at highway speeds as low as 208.
I will be flushing the system tomorrow to check for rust and blockage. I suspect either the system has air in it or there is a blockage in one of the radiator banks.
I dont believe its the water pump as I had that out when I did the P.I. swap and it looked alright.

The fan however may have been the issue. I checked my wiring today and I had wired it up witht he positive fan wire going to just the orange/blue wire from the car. I suppose this means the fan was only turning on when the computer switched the high fanspeed wire on. I now have both wires spliced together so it should remain constantly on. I drove it around a while after the fix but it still seemed to be getting hot at idle so in any case i will see if a flush helps. Thanks for the replies, let me know if you guys come up with something else.
 

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flush the radiator would be a start if you havent then if it comes down to it replace parts you changed with the stock ones one by one and see which one it may be(last resort)
 

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+1 on the 180 thermostat. I just put on in my 96 and it made a big difference. Still sounds like you have a problem with either the radiator, fan, fan shroud. Under drive pulleys are a moot point since he is ideling at around 700-800 rpm, that is ideling higher than stock and would make up for any underdrive.
 

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Let me know too, i have had a slight issue since i change my tstat. Not over heating, but not running as cool as it should
 

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radiator flush than replace the thermostat. They cheap and fail all the time. I went through a couple on a 455 bb couple yrs ago.
 
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