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Discussion Starter #1
I have a suspicion that my temp gauge is not reporting accurately. How close to coolant temp would the thermostat housing or heads be if I measured them with an infrared themo?
 

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The intake manifold near the temp sensor would be the best place to gauge the meter's accuracy. If the coolant is low enough for the temp sensor to no longer be immersed (or trapped air), the gauge will also read lower than the coolant temperature.
 

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Discussion Starter #4
My temp gauge will often touch 220-240 and I find it hard to believe. Water pump, radiator, hoses, and shroud are all new, stumped as to the problem but suspect the gauge is inaccurate. I'll check the intake manifold near the t-stat this evening.
 

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Back up a minute and tell us what conditions it is overheating under: in traffic, at highway speed. A guy I work with had a 68 Cougar with a 302 that would overheat on the highway. He changed the pump, thermostat, radiator, even the torque converter. He took it to a speed shop where they tuned it on a chassis dyno. Still overheated on the highway. He changed the fan blade and the problem went away. Which seems counter intuitive since I always thought the fan was just parasitic drag above 40 MPH. I still can't believe it was just the fan.

Have you checked the thermostat?
 

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Discussion Starter #7
The car has "overheated" (on gauge) on the highway and on sidestreets though has only boiled the coolant when I push the motor hard for about 10 miles or drive it more than about 20 miles. I know there is a problem but I do want to have an accurate reading to help the diagnosis. As far as the motor goes. the only things I can think of would be a blockage in the block or a problem with the heads or gaskets.
 

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The car has "overheated" (on gauge) on the highway and on sidestreets though has only boiled the coolant when I push the motor hard for about 10 miles or drive it more than about 20 miles. I know there is a problem but I do want to have an accurate reading to help the diagnosis. As far as the motor goes. the only things I can think of would be a blockage in the block or a problem with the heads or gaskets.
the engines is ? what stock/high mile to full blown street racer

when did over heating start ?
 

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Discussion Starter #9
Sorry the motor is a stock '66 289 with 16x,xxx miles. I believe it was overhauled about 20,000 miles ago (before I got it). It has been indicating a hot temperature since I installed the temp gauge in April. When I checked the temp at the intake manifold with my infrared it shows about 20-25 degrees cooler than the gauge is indicating.
 

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I would try venting the cooling system you may have some traped air. What temp is your stat? Lower hose could be colapsing. Do you have a fan shroud? How old is the radiator?
 

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Discussion Starter #11
I would try venting the cooling system you may have some traped air. What temp is your stat? Lower hose could be colapsing. Do you have a fan shroud? How old is the radiator?
The t-stat has been pulled (after trying two and testing both), the lower hose is new and does have a spring in it to prevent collapsing. The radiator is a year old and does have a shroud on it.
 

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Sorry the motor is a stock '66 289 with 16x,xxx miles. I believe it was overhauled about 20,000 miles ago (before I got it). It has been indicating a hot temperature since I installed the temp gauge in April. When I checked the temp at the intake manifold with my infrared it shows about 20-25 degrees cooler than the gauge is indicating.
get a high quality mechanical gage
25 degrees difference , one of the instruments is off
 

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Discussion Starter #13
get a high quality mechanical gage
25 degrees difference , one of the instruments is off
I checked the gun on a glass of ice water and it read 32.6 degrees. That's how we make sure our thermometers are accurate at the restaurant so I don't think it would be any different with this device. Looks like I'm going to get a new gauge.
 
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