Hi y’all

(I’m new here so go easy on me lol)



I seem to be having a cooling issue with my f-250. (’89 7.3idi – ZF5 trans, 4x4) the Coolant temp gauge is pinned and the red “engine” idiot light is on.



A couple weeks ago it was very hot, about 95 degrees. I was driving normal on the highway and the temp gauge was higher than normal but I pressed on. Once I got to pulling a slight grade my rad boiled over and that was basically the end of my trip. Now even when I start it cold the temp gauge is pinned and the light is always on. Not sure what caused my overheating situation or why the lights are still on.

All the cooling system components appear to be in good shape.



I searched the forums but couldn’t find anything that was relevant to what I’m experiencing. If anyone can offer some insight I would really appreciate it.

 

Be skeptical of the OE gauges that came in our trucks. They are notoriously inaccurate. That being said, if your radiator boiled over you definitely have a problem. Check the condition of your coolant. It doesn't have any oil mixed in it, does it? You can also use test strips to ensure your coolant has the proper amount of SCAs. The 7.3l IDIs sometimes suffered from cavitation after a lifetime of abuse without any SCAs in the coolant.

 

I had a similar issue with mine, turns out the warning light sensor was shot. There are two coolant temp sensors on these engines. One is for the gauge, the second is for the dummy light. If the dummy light trips, it pegs the gauge as well to try and really get the attention of the idiot driver before something worse happens.
I can't remember which sensor is where on the engine head, I want to say drivers side front.. Someone has a nicely done picture with them labeled. If you look and disconnect the wires, its should be easy enough to figure out which sensor it is. Cheap and easy to replace, I'm not sure if its a 'feature' or just old age breaks the sensor if it gets too hot, then doesn't reset once cooled down.

Actually I lied, there is a 3rd temp sensor on the passenger side head, but that's just for the cold start and fast idle solenoid and doesn't affect the gauges at all.

 

So I've got an 88 idi f250 with the 7.3, zf manual trans, and when I start it up and drive it for a short while(about 10 minutes or so) it gets pretty hot, according to my temp guage. Around the A or even the L. But if I turn it off after it's gotten that hot, wait 5 minutes, and then restart it, it runs at normal (needle on the O) temp. Can't figure it out.

 

If your truck is overheating then it’s probably your thermostat/water pump.

 

^^^x2^^^

If you replace the thermostat it's best to get a Motorcraft replacement. Our IDIs don't use a standard Stant style thermostat.

When you R/R the water pump one of our member; genescripter, has a website with detailed instructions. It's CRITICAL that you use RTV sealant on the proper bolts.

https://www.nickpisca.com/diesel/

 

start with the above, and add a aftermarket coolant temp gauge. I would also recommend replacing the radiator cap with a napa brand one. it is a rebranded stant radiator cap. they are the best.
also have you ever heard your fan clutch lock? if not definitely time for a new one.

 

my 88 has 496,000 miles on it and i have NEVER heard the fan clutch lock.
the gauge and light sensors in these trucks are basic on/off switches.
put a real temp gauge in it and see what is really happening.
5 minutes sitting is no where near enough time to cool a system.

 

Get an IFR Temp gun to see how hot things are.
Here is a Google search, pick your favorite flavor.

https://www.google.com/search?q=IFR+...ih=536&dpr=1.2

An after market water temp gauge will also tell what is really going on.


Charlie