[Unit227]

Alright so while driving my 04 f350 last night I noticed the fan kick on and I looked at my water temp on the a pillar and it was still bottomed out at 100f. Then about 2 minuets later the check gauge light came on. I was able to pull over and shut it off about 3 seconds after the light came on so I don't think anything is damaged, although a small amount of coolant did spray from the reservoir. Then I switched the key to the on position and after the gauges did their full sweep it went right to 260. I waited for it to hit 200 and restarted it. It started and ran just fine for the rest of my drive that night. I didnt even hear the fan go on once during my drive either. (Although I was being very careful.) One thing I did notice on my drive home was the gauge would jump to about 198 then slowly fall down to 160 then jump back again. Any ideas on what could've happened? It starts and runs fine and didnt throw any codes so I have no idea.

 

[bismic]

Thermostat maybe?

You might also check to verify that your degas bottle (coolant system) has a level and will hold 10-15 psi of pressure.

 

[Unit227]

Thermostat maybe?

You might also check to verify that your degas bottle (coolant system) will hold 10-15 psi of pressure.

Ill see if I can pressure test it today, I did notice that the gauge on the pillar is for the water outside the block as my scan tool was at 210 while that was still at 100 this morning.

 

[bismic]

The temperature "outside the block" is probably the inlet air temperature

 

[Unit227]

The temperature "outside the block" is probably the inlet air temperature

No it says water temp on the gauge

 

[bismic]

That pillar gauge can read anything - doesn't mean it is right. Maybe it is *C.

There isn't any water in the truck that will be 100*F, once it is heated up.

 

[JUGERNAUT]

If your pushing water out the degas and temps are all over the place most likely you have bad head gaskets also when a Ford thermostat on diesels go bad they revert to open status! This means when your stopped the temp will raise not so when going down road it will cool down. The only time temps with fluctuate is when exhaust gasses enter cooling system and puddle by ect sensor.

 

[Hydro]

From your description, coolant is not touching the temperature sender part of the time -- either low coolant or an air pocket at the sender.

air pockets can be caused from head gasket leaks -- or from lack of coolant flow (broken water pump) causing the coolant to boil from hot spots
the two air vent lines connecting to the degas bottle need to be checked for obstruction as well -- their purpose is to help with trapped air in the engine

 

[bismic]

I have a hard time believing that even if the probe/sender were in a vapor bubble inside the coolant system that it would read 100 *F when the liquid inside that same system is 200+ (assuming the gauge is working properly), but I guess anything can happen. I can definitely see it causing fluctuations though. The 100 degrees (seemingly stable) just doesn't sound right.
Knowing the location of that probe would help - if it is in the degas bottle and the degas bottle were totally empty might explain it.

 

[Hydro]

I agree, that the aftermarket gauge should be verified, and the sender replaced -- Is the factory gauge still working at all? Assuming that this truck had a factory gauge.

Hmm, where is the pillar gauge sender located on the engine?

 

[Unit227]

Temps aren't all over the place, it just steadily keeps rising until I shut it off, then the gauge will work correctly and the truck stays in normal range

 

[bismic]

Personally, I don't like pillar gauges, but I always assumed that people tied into (electrically) the factory sending unit for those parameters that had them (eg coolant temp), but that wouldn't be considered outside the engine.

 

[Unit227]

Temps aren't all over the place, it just steadily keeps rising until I shut it off, then the gauge will work correctly and the truck stays in normal range

In fact it would actually cool down by a couple degrees when idling

 

[Hydro]

In fact it would actually cool down by a couple degrees when idling

Possible a slipping water pump impeller in this case

 

[bismic]

Is this the 04 you just bought?

 

[Unit227]

Is this the 04 you just bought?

Yes, was fine the whole hour drive home and the whole week prior

 

[Unit227]

UPDATE: thermostat and upper radiator hose were leaking, its fixed and running great now.