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Discussion Starter #1
Stats: 02 BLACK Crew Cab Fronty, V6, 255/70/R16 tires if that helps.

OK, so down here in Texas...where as we all know...it's 110 ish degrees during most of the day.... My truck seems to CONSISTENTLY overheat.

I could be sitting in the shade, I could be driving through town, or I could be driving on the highway...I turn the AC on, and BAM! within 30 seconds the temp. gauge goes from 1/3rd of the way to almost striaght up and down, and then the AC gets hot.

From there, If I turn the AC off, it'll slowly go back down, but most of the time it stays constantly very hot.

All of the fluid levels are fine, I've had a recent oil change, and once again it's freakin hott here!...

Any ideas?
 

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Sounds like a plugged thermostat. Did you check it?
 

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I am not familiar with 1st gens but the Thermostat is usually on the engine where the top radiator hose goes in. You would need to drain the coolant below the top hose level and pull the thermostat. You will know right away if it is plugged. It should be clean and move freely.

90% of the time that I have seen, repeated overheating is caused by a bad thermo. Usually it just doesn't open when it should and the engine will overheat because coolant isn't flowing through it.

I used to live in the California Desert and even on 116 degree days I was fine with A/C on and towing a boat. You should be too.
 

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Discussion Starter #5
Thanks. I'll check that and then post tomorrow to see if it works. If you have any other sudden impulses on what you think it might be, post it please.
 

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Will do. Google yourself a service manual to make sure you know exactly where the thermo is, since I am not familiar with 1st gens but in my history, changing it out is one of the simpler things to do.

I would recommend getting a replacement thermo to have on hand so you can swap it out. They aren't expensive and you can always return it if it isn't it.

An undercharged A/C can also cause overheating but since you said it is always running hot then it probably has nothing to do with the A/C.
 

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How many miles on the truck? Sounds like you might have a bad fan clutch.
^x2. Check to make sure your fan is running when you notice the overheating. I had a Jeep that ran into an issue of a bad fan relay (which caused the fan to sometimes not come on) which in turn would cause it to overheat pretty quickly when I was sitting at a stop light or something. Does the overheating only seem to occur when your standing still (or else barely moving)? Or does the temp start to drop if you start driving fast enough to move air through the radiator? If so, a fan issue is likely.

I should note that I am not familar with 1st gens, so I won't be of much help beyond this point, but thought the problem sounded familar.
 

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Mine does that, but only on a really hot day, sitting in traffic, w/the a/c on. My guess would be the radiator cap, but I haven't confirmed that.
I've done the a/c-defrost mod, so when I start to overheat I can turn off the a/c, put the selector in defrost, and turn on the heater. Cools down the engine pretty quick. Heats me up a bit, but it's a dry heat. :)
The t-stat is on the lower radiator hose, at the engine block. A real pain to change. If your not overheating any time other than when you're running your a/c, then I wouldn't think the t-stat is at fault. Again, replace the cap and go from there.

Whitewolf mentioned an undercharged a/c might cause this. Hmm, could that be the problem? My a/c's not the best, so it might be undercharged. I was thinking the thermo amplifier was my problem w/that, but undercharging could also be a possibility.
Anybody w/professional a-c knowledge wanna jump in here and confirm this?

Meantime, change the radiator cap. Cheap enough. I'll do mine this afternoon, since I'm goofing off from work and need something to do.
 

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Mine does that, but only on a really hot day, sitting in traffic, w/the a/c on. My guess would be the radiator cap, but I haven't confirmed that.
I've done the a/c-defrost mod, so when I start to overheat I can turn off the a/c, put the selector in defrost, and turn on the heater. Cools down the engine pretty quick. Heats me up a bit, but it's a dry heat. :)
The t-stat is on the lower radiator hose, at the engine block. A real pain to change. If your not overheating any time other than when you're running your a/c, then I wouldn't think the t-stat is at fault. Again, replace the cap and go from there.

Whitewolf mentioned an undercharged a/c might cause this. Hmm, could that be the problem? My a/c's not the best, so it might be undercharged. I was thinking the thermo amplifier was my problem w/that, but undercharging could also be a possibility.
Anybody w/professional a-c knowledge wanna jump in here and confirm this?

Meantime, change the radiator cap. Cheap enough. I'll do mine this afternoon, since I'm goofing off from work and need something to do.
For you, I would do the thermo amp mod first man... Im ordering mine today. If that doesn't fix it, then go fwd and try to charge the system... Start with the easiest and cheapest options... If you try to fill it yourself, you run the risk of not having a proper mix of freon and oil and or overcharging...

Stats: 02 BLACK Crew Cab Fronty, V6, 255/70/R16 tires if that helps.

OK, so down here in Texas...where as we all know...it's 110 ish degrees during most of the day.... My truck seems to CONSISTENTLY overheat.

I could be sitting in the shade, I could be driving through town, or I could be driving on the highway...I turn the AC on, and BAM! within 30 seconds the temp. gauge goes from 1/3rd of the way to almost striaght up and down, and then the AC gets hot.

From there, If I turn the AC off, it'll slowly go back down, but most of the time it stays constantly very hot.

All of the fluid levels are fine, I've had a recent oil change, and once again it's freakin hott here!...

Any ideas?
The thermostat is a PITA man... but its doable.... How many miles do you have on your truck? If your getting close to 100k, I would just do a water pump/Timing belt/thermostat change... all of these things need to be done before 115k and should be done closer to 100k.
 

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I agree w/XE King about doing the belt, etc., if it's time. If you go this route I'd also remove the t'stat housing, where it bolts to the block, and reseal this. I had a major leak develop there, a couple of years after I did my belt. It's more work to seal that, from scratch, than it was to do the timing belt. Plus, you can't see the rust that forms there until you remove the housing.

XE, the reason I think I've got a bad thermo is because I had my a/c charged, at a shop, after I did my heater core (had to pull an a/c line to get it out). No change after the recharge. It's been p*** poor since day 1.

Gonna get me a new cap this afternoon. Keeping my engine cool trumps keeping my butt cool.
 

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How many miles on the truck? Sounds like you might have a bad fan clutch.
This thread got me looking a little closer at my '01 sc w/160k (only overheats when I'm sitting in traffic, on a hot day, with the ac on). Spent $18 on a radiator cap (dealer bent me over, again). Needed it, but that didn't address the problem.
Checked my clutch fan, after a long run in heated traffic, and found that it was freewheeling. I think that thing should've been locked up. Those things aren't cheap, so maybe it's time for an electric. I'm hesitant because because I've read a few negitive things on here. Couple of extra horses wouldn't hurt, tho.
 

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Discussion Starter #14
I just broke 100K, and no I still have not got it fixed. I've flushed the cooling system, had it recharged, checked to make sure the fan is running when i'm just sitting there, and it still doesn't seem to keep it from overheating.

I'll probably try the radiator cap exchange, but I doubt that will work.
 

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I just broke 100K, and no I still have not got it fixed. I've flushed the cooling system, had it recharged, checked to make sure the fan is running when i'm just sitting there, and it still doesn't seem to keep it from overheating.

I'll probably try the radiator cap exchange, but I doubt that will work.
Did you ever get the thermostat checked, or replaced? In Texas, i think I would opt for a cooler tstat. How are the hoses? I know you've had the system flushed, but when you pull the cap and look down into the radiator, do the coils have a lot of deposits on them? Not sure if anyone asked, but do you have an electric fan in front of the AC condenser and is it working when you turn on the AC? It's an unlikely scenario, but are you sure the temp sending unit and gauge are working correctly? If you can, double check the temp with a temp gun. Just some thoughts.
 

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it may be that there is nothing wrong with your truck.

the cooling system in these trucks absolutely sucks.
 

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Just a heads up... just because the fan is spinning doesn't mean it's working properly. When it's cold it should spin pretty easily but once the engine warms up you should notice a little more resistance. The fan clutch is designed to allow the engine to warm up and as heat transfers into the clutch it starts to stiffen up and increase the rpm of the fan i.e. less slippage in the clutch.
 
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