So ai am having an overheating issue I am chasing. The trucks works as normal until towing heavy. Even then it does ok until pulling grade. It used to heat to about 220 and sit there all day no matter how hard you pushed it.

Earlier this summer it was towing fin and then started to not be able to stay cool. I put in a fan clutch and t stat and thought it had fixed it. Now it takes about 30-45 min to get show up. It gets warm as normal, then towing it will sit like 235(which it never saw ever before) and when you hit grade, it starts to climb. If you are on the flat it can sorta run ok, but at 235..

My next guess is to do a water pump and radiator flush?

 

My suggestion maybe wrong, and most likely will be, but, on all of my vehicles, I change my radiator out every 10 years.I cut one of mine in half a long time ago and was flabbergasted at the amount of corrosion that had built up over the years, even with maintaining the correct fluid.
Thermostat and water pump replacement are always a good maintenance procedure, especially after 20 years of service.

 

I really hope that you missed a zero there……………..

 

Not gonna want to hear this...but when mine did that, it was a blown head gasket, venting hot exhaust gas into the coolant. They did a block check and found it that way (no other symptoms other than overheating and coolant blow-off through the degas bottle (but only a little bit).

Now HOPEFULLY in your case it's just the sensor and not a blown head gasket or similar.

How mine went down...

Towing on a 100+ degree day (on the flats), AC on ('cause, well, it's hot outside)...suddenly motor goes into limp mode and overheat lights/SEL illuminate, temp at 232 via the SCT tuner. Find coolant blow-off under the hood. Fan LOOKED like it was spinning...it was freewheeling - lost the fan clutch. Was able to cool down and restart...drove about 5 miles and overheat lights (no limp mode) again (230). Swapped the trailer to another vehicle in the group, and got it home with more than a few overheat lights. Swapped the t-stat, fan clutch and water pump. Still getting overheat lights, but only at 210-220. Then a pinhole leak in the radiator plastic top bit. Swapped the radiator. Still getting intermittent overheat lights again 210-220. Degas bottle would blow off until about an inch below the min line, then would stop. I noticed when the light came on, if I downshifted (higher RPM) I could get the light to go out. A little research brings up the idea of a 'bubble' of air in the head if you don't vacuum fill after a radiator swap, so I bought a vacuum fill kit and swapped the t-stat down to a 175. Started running temps around 205, with the occasional overheat light.

Took it to a shop to swap the plugs and the back two COPs (chasing down a rough idle)...he sees the plug on #7, does a block check test, confirms a blown head gasket. I put in some of that sealant and nursed it a few days until I could get a new motor delivered.

SIDE NOTE: Up until the motor swap, I could NEVER get the radiator fluid NOT to be milky brown, even after about 4 flushes...so much crud had built up since 2000.

Had the motor swapped out. Took it back from the shop...overheat light on the way home (at 202). I'm livid, take the rig back...per the shop he flushed another 4-5 times and couldn't chase down the issue. I told him look, the gauge pegs and the warning light comes on, but the SCT says the temps are below the line...so to me that says there are two ways the rig senses temps...a sensor that pings the dash to turn on the light and peg the gauge...then another sensor that the computer uses to calculate it's mix and all of the rest. I asked him did he swap out that sensor...he finally agrees. $25 dollar sensor, no more light.

If you are not seeing any coolant blow-off, I would look at that sensor and a quick block check (very quick to do) to rule out a head gasket issue. Maybe you'll get lucky and it will be a bad sensor.

 

Thanks. I sometimes get brain fog and write what is something in between what I really meant.
I edited my post to read every “10 years”, but every 100,000 miles is a good one, also.
Jeez, I got get tested.

 

that way..good chance you will never be stuck with a cracked radiator.. my daughters mustang radiator cracked 1 year after replacing..so no garuantees with chinese stuff ha?

 

If you're willing to drop $62 to know, you can figure out real quick if its a blown head gasket (or cracked block/ head) putting combustion gases in the cooling system.

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