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Discussion Starter #1
My 90 has been having issues with the getting hot sitting in traffic or when I run the ac. I just replaced the fan clutch and recored the radiator and added a 4th core. A few times sitting in traffic the needle went almost in the red without the ac on. Even at highway speed with the ac on the car will still go to about 3/4 the way to the red on the gauge. Any idea what this could be?
 

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Water pump.
x2 on the water pump. I suggested this in another post but others seemed disagree. My issue was only when climbing this one particular mtn pass. But as soon as I replaced it the problem never repeated itself. Guess I was lucky.

I think others had had issue with cores being too big and not effective. You might search for this issue here to see if that sounds like what you've got going.
 

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Some say the 4 core hurts as the last row doesn't cool sufficiently. I went with a 3.5 rad, new viscous, and external oil cooler, and have gotten back to center. And I have a fairly spicy 4.6- still will move to 3/4 under hard use, but cools right down, and no issues when stopped/sitting. Working for me.
 

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Have you checked your thermostat? It might be stuck. Since you just did the rad work, I'm assuming your coolant level is good.
 

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Sorry nothing to add to help this case but I am interested to hear about water pumps.

It seems to be a very simple design with a pulley, a bearing and an impeller that moved the water.

My only experience with failed water pumps is when the bearing dies (and the "pump" makes noise/coolant leaks out).
How would a water pump lose its capabilities over time? I would not think coolant is abrasive enough to eat up the impeller.
What's the difference between OEM and other lesser part in term of the impeller (yes bearing could be lesser and die prematurely).
 

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You've got a '97 which should be OBDII. For the love of God just get a Bluetooth plugin and phone app so you can see the real temperature. $30 should get you both and you don't have to wonder just how hot your truck really is.
 

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Make sure you wanter pump and thermostat work as should. Check coolant flow. If you still have coolant flow issues then you have a clogged heater core. Disconnect both heater core hoses and run a garden hose through either one and notice the flow. If you see crud come out keep running water untill it clears. If you cant unclog it find a shop to rod it out or replace it.

20 minutes after it reaches operating temp in stop and go traffic pull over and look at tye upper radiator hose. If its swollen and hard its a sure sign you have a cracked block or blown head gasket in one of the heads!
 

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Second what Brett says. Have the GoPoint Bluetooth dongle; extremely precise.
Extremely precise assuming the sensor is providing the right information.
 

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Discussion Starter #17
I'll look into the Bluetooth thing.. This morning I had the issue again. Didn't have time to jump out and check the top rad hose. Truck gets hot and you can hear the engine get louder. also I noticed I'm getting a ticking noise that sounds like it's coming from the passenger side footwell. Even when I shut the ac the temp didn't start to drop after.
 

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Water Wetter might help until you make necessary repairs
The misconception that water wetter is better than coolant comes from racers using it in bikes and cars on several tracks. They use it because coolant containing propylene glycol is very slippery, is akin to black ice on a track and is banned at most tracks! You may see, and its a big maybe to get a 5-10degree reduction in temps in extreme racing conditions. Most people experience no dicference in temps with water watter and some have even reported lower temps with just plain H2O compared to water wetter. Your milage may vary.
 
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