Random Overheating?

[pzy3339]

Twice this year I have had my temp gauge go to the red line and my temp warning light come on. Its an all of the sudden thing. The fan is always roaring when this happens.

Truck is driving fine, make a stop and then the temp starts climbing super fast. Pull over and shut down for maybe 5 minutes, start it up and temps are back to normal and everything is ok.

First time this happened I put my hand into the fan air to feel how hot it was, pretty warm but not blazing hot like I would expect from an overheating engine. Seemed normal temp.

Few things I am thinking about.

1) The AC has been on during or just prior to this both times.
2) The truck has been running for a prolonged period of time and lots of stop and go both times. Never happens during my daily commute to work or a short trip here and there.
3) Coolant loss was a problem when I bought the truck a year and a half ago. Never left any on the ground but I would need to refill the tank every few months. Very slow leak, I believed to be a pinhole somewhere in the radiator so I put liquid aluminum in the radiator. Have not lost a drop of coolant since.

I believe this to be a sensor issue. The temp rises and falls too fast. I do not believe it to be possible for the engine to drop back to normal temp that fast when I shut it down. Seems more like a bad reading.

The truck has 143,x.. miles on it now. Normally runs like a champ.

 

[RJ]

Feel (carefully) the temperature of the air coming out of the radiator when the fan is roaring, this tells you if enough hot coolant is circulating through the rad.

What you may have is a partially stuck thermostat - the computer won't know that, and simply kicks the fan into locked high speed. Barely any hot coolant is flowing through the rad, and you simply end up with a rad full of cold coolant, and an engine full of hot coolant.

When you shut of the engine, some times the thermostat cracks opens a bit, and a rush of cold coolant from the rad pours into the engine to cool it.

So carefully check the air coming out of the fan. An engine only generates so much heat, so if coolant is flowing properly, and the fans is roaring, that's almost impossible - your engine would be cooled down to 150 degrees. So something, somewhere, is blocked...

 

[pzy3339]

I replaced the thermostat. Have never done that before so I don't know what to expect from an old one but I can say the spring rate feels much higher than the new one. Quite a bit harder to press it together.

Also bought a new sensor which I will install if I see this issue happen again.

 

[96743explorer]

did you buy the same exact thermostat (oem) since you are comparing spring tension?

 

[RJ]

I replaced the thermostat. Have never done that before so I don't know what to expect from an old one but I can say the spring rate feels much higher than the new one. Quite a bit harder to press it together.

Also bought a new sensor which I will install if I see this issue happen again.

Spring rate alone won't tell you a whole lot. It's designed to work in tandem with the thermal expansion wax in the cylinder. Perhaps the new cylinder has a larger surface area, or the wax expands more...

Test our old one in a pot of boiling water for fun. Chances are it doesn't open nearly as wide as the new one.

 

[madcanvis]

Similar problem here (2007 EB 90k miles) but the it'll over heat within the 1st 2 miles and not all the time. Random occurrences too. Turn heat on and the needle drops as fast as it climbed. Changed thermostat (NAPA part) and burped coolant lines. Problem returned.
I'm thinking a full flush of heater core and coolant lines (calcium flakes clogging and dislodging).

 

[Boomyal]

Similar problem here (2007 EB 90k miles) but the it'll over heat within the 1st 2 miles and not all the time. Random occurrences too. Turn heat on and the needle drops as fast as it climbed. Changed thermostat (NAPA part) and burped coolant lines. Problem returned.
I'm thinking a full flush of heater core and coolant lines (calcium flakes clogging and dislodging).

Check your overflow reservoir (or radiator cap and neck) for any signs of exhaust smell or residue. I have this problem on a '97 E150 4.6. Turns out there is a crack somewhere letting exhaust gas into the cooling system. From start up the gas would build up behind the thermostat and keep it from opening gradually. Finally with the turbulence of boiling coolant, it would reach the bud (on the thermostat) and open it, allowing coolant to spew out into the hot engine and then blow out the coolant cap. It would never show hot on the gauge until after the thermostat finally opened. I would shut the engine off, wait a couple of minutes, then start it up and go on my way.

My solution was to drill a 1/8th" hole in the top edge of the thermostat. This would let the gas out, the warming coolant in, and it never blew it's top again. During the course of driving I could hear the built up gas whistling out the coolant cap, so to keep the system from pressurizing I just unscrewed the coolant cap, a few turns. I have been running like this now for 3-4 years with no problems. My plastic coolant reservoir, is black and greasy, but hey....

Keep in mind, in my case, this overheating only ever happened a few miles after start up. Once the thermostat was open, it never overheated. Your miles may vary.......

 

[pzy3339]

did you buy the same exact thermostat (oem) since you are comparing spring tension?

Yes, bought it from Ford.

 

[tripplec]

Thermostat is normally the main culprit as already stated above for you. Vapour lock or Air pocket can cause grief in some engines and require burping the air out. Sometimes getting the front up high like on ramps or a steep hill and popping the rad cap will allow air to find its way out. Run it like that with the cap off and see if burps of air come out.

Since you used a Ford thermostat it should have the hole in it. It needed to be installed UP as well.

If its overheating (gauge reading high) the fan should be roaring at a much faster rate (as already stated).

 

[pzy3339]

Just an update. 2 months since I changed the thermostat and the issue is gone. I never bothered to change the sensor.

I did burp the system after reinstallation and I used some generic multipurpose coolant.

 

[Sip]

Similar problem here (2007 EB 90k miles) but the it'll over heat within the 1st 2 miles and not all the time. Random occurrences too. Turn heat on and the needle drops as fast as it climbed. Changed thermostat (NAPA part) and burped coolant lines. Problem returned.
I'm thinking a full flush of heater core and coolant lines (calcium flakes clogging and dislodging).

What’s the problem for you? I’m having the same problem.