over heating issues

[Readyforduty24]

i have a 90 3/4 ton 4x4 with a 350 standard tranny in it. thing is over heating but i'm not losing coolant any where............. i'm confused as to how this is happening. the only thing i can think of that would be causing my gauge to read as over heating is the coolant temp sensor. has anyone else had this issue? if so where should i start my search for the issue?

[Eyegore]

This happened to me, it turned out my radiator was restricted, higher rpm should cooled it but made it overheat. Check radiator adn thermostat.

[Readyforduty24]

ok thanks man, i live in the panhandle of nebraska and its been hotter then normal around here. over 110 some days yesterday was the hottest day and thats when it started to do this.

[Mr_Rich]

Take a hose and rinse your radiator through from the backside. You'll be amazed at all the garbage that collects in the cooling fins. I rinsed my rad. and when I finally removed it for my engine install I still washed a LOT of crud from the cooling fins. This should be a summertime maintenance routine.

[ChevLoRay]

In the same way that crud builds up on the radiator, it will have built up on the AC condensor. Even if the AC doesn't work, that will also block the movement of air thru the condensor and the radiator.

[Boog]

The fan clutch may be getting weak. Also is the fan shroud in place?

[Readyforduty24]

yea the fan shroud is in place, clutch felt like it always has it moves but does not spin freely, i did rinse out the rad but did not do it from the back side so i'll try that today. i replaced the thermostat it still over heats just not as fast now hahaha. thanks for all the help! gives me a few places to start looking.

[Kim57]

When mine started over heating I changed the thermostat and the radiator cap.
That cured my problem. Seems the cap wouldn't hold pressure any longer.
Kim

[Readyforduty24]

i changed the thermostat, and the cap as they are the cheapest to replace and its still over heating. the only time i can get it to cool off is if i pop the hood and run the heater full blast then it'll cool off to normal temp. if i don't do these it'll over heat to the point of the gauge pegging out. it doesn't boil over either. i've sprayed out the radiator and condenser several times today. still no change.

[gregory5000]

Does it appear to be overheating in the engine compartment? It sounds like you may have a gauge issue. If the gauge is going to the max that is like 260 degrees. I may be off base not having all the info, just an observation. Hope it is just a gauge issue.

[Readyforduty24]

yea thats what i'm hoping, tomm. when i get to work i'm goin to test the ohms on the sensor and see what it reads...... hopefully its just that.......... ugh.

[Readyforduty24]

so i used a thermotemp gun on it to get a reading on the water temp. when the gauge was saying the engine was over heating. well either the sensor is bad or the gauge is bad, because the temp of the coolant at the thermostat housing was 191 degrees and at the lower hose it was 141. so now i know its not the engine lol.

[ChevLoRay]

Now that you know the temps, I gotta ask...have you done a pressure test on the system? Even if it isn't leaking, at least you'd know if there was a weakness.

But, at least you know more than your guage is telling you. I just use my guage for a reference point. My radiator started leaking and I replaced it a couple of weeks ago. Pressure test showed me where the weakness was.

[Readyforduty24]

no i haven't done a pressure test as of yet........... i'm thinkin i should though.