Hi
2001 PSD with 100,000 miles, MN 80 degrees. I took it in for a new oil pan install.
Now it is over heating, It will run normal for aprox. 30 miles then the temp will start to climb rapidly "30 seconds" from normal temp to red.
If I turn the heater and fan wide open it will go right back to normal in about 60 seconds, it will run normal for a few miles than it will do the same thing. I changed the thermostate but it made no difference. Any ideas?

 

Have you talked to the shop that did it? I wonder if they got the oil cooler plugged up during the swap? Of course it could also just be a bad sensor. I assume you have verified the coolant level is good.

 

I test drove it and it overheated, they changed the thermostat but it still over heated and they said it must be a bad head, but don't believe that. Could there be some kind of sensor they forgot to reconnect?

 

Check the wire from the coolant sender to make sure it isn't pinched somewhere and grounding out. And as mentioned your gauge could be lying, you need to verify if you are really overheating.

 

Seems like when you turn the heater on now it gets more cooling capacity like a radiator. I use to do this in a 62 facon rancho. I bet your radiator isn't flowing correctly and mitt need to rod out or replace. I don't believe it would be a sensor if it cools down with the heater on. Could be wrong but doesn't make since to me.

 

its been mentioned that the parts store thermostats dont work good with these trucks,do you know which one was used?

 

Is it possible the block could be air bound? Hot air won't open a thermostat. Maybe pull a heater hose and see if it'll take more coolant? Make sure the serpentine belt is routed properly. If the water pump is spinning backwards it's useless.

 

1. Is this the dash gauge or from a scan tool? If it's from a scan tool, ignore it and focus on the dash gauge instead... there is no coolant temp on the OBDII port and the reading lies.
2. If it's the gauge, verify reading by aiming a laser thermometer at the sensor (near the thermostat). I bought a laser thermometer at Radio Shack for a very reasonable price and it proved to be accurate.
3. Check your degas bottle. Is soot (or anything other than coolant) in the bottle?

 

Im assuming the motor was removed for the swap. I would go back to the shop and demand they fix it, the problem wasn't there until they touched it right? I suspect a clogged oil cooler or a very large air bubble trapped in the system. Make sure they use only the OEM Motorcraft T-stat, some cheap auto parts stores don't have the little air check valve built in.

 

I second that, they did something to it, they should fix it.
That being said, fan clutch maybe?

 

I am gonna go with air in the lines. Is the degas bottle full?

 

My first thought is to lean towards something the shop did as well. Generally the engine has to come out for a new oil pan, so a lot could have happened during the process.

IIRC, the dash gauge is a "dummy gauge". That means it slowly climbs to the center position, then stays there until it gets to a certain threshold, at which time it quickly climbs to redline. When it cools below that threshold, it quickly reverts back to the center position. If it is hovering at the threshold, it could only change by a few degrees one way or the other, but the gauge changes from "normal" to "redline" giving the impression of rapid heating and cooling. Someone correct me if I'm wrong on that...

 

Where in MN are you? Maybe one of us locals could help.

 

Ditto! Be gald to help if we can.

 

As best as I can tell from observing the dash gauge on trucks that also have an aftermarket coolant temp gauge and also experienced overheating....

The factory '99-'01 temp gauge has 4 positions. Cold, normal, hot and red.
The gauge appears to remain in the cold range until coolant gets around the 130-140 degree mark then it start it's trek to the normal position. It remains rock steady in the normal position from about 150-230 degrees. The fan clutch can cycle on and off and that factory gauge wont budge one bit.
Around 230-250 range moves the gauge to the third position, which is at the very upper limit of the 'normal range' region on the gauge....just a needle's width below the hash mark next to the red region.
The fourth position is the red region. Needle will be straight up at 12 o'clock. When in this position, a light illuminates on the dash asking you to 'check gauges' (or something to that effect).

If you ever run your truck in that red area....then you have shot your first bullet as far as the plastic tanks are concerned. The radiator shop recommends replacing the tanks if the system ever gets that hot. The guy I spoke with said those plastic tanks have one or two heat cycles in them before they warp and fail. I got two cycles out of mine and then I was waiting on the side of the road near the AZ/CA border waiting for another radiator to be delivered.