Hi,

My F-250 with V10 has developed an overheating problem.
While driving, the temp gauge suddenly shoots to max, and the truck goes into limp mode. Turning off the truck and ignition, waiting a few minutes, and all seems to be well again - sometimes for only a minute, sometimes for several days. No steam leaking, the water in the reservoir seems to be normal temperature, the radiator is not overly hot, and the AC keeps on blowing ice cold.
Me thinks it is not really overheating, it just thinks it is.
So where to start? Change the temp sensor first, or the thermostat? It seems the hoses are fairly firm, I don't believe they are collapsing from suction.
Any advice appreciated!

Berrie

 

It IS overheating even though it might not seem like it. Get a new 190* MOTORCRAFT thermostat and a new cap and your problems should be over.
(You need to put your location in the upper right corner.)....................welcome to F.T.E.

 

"Change the temp sensor first,"

Yes.
Then flow test the radiator.

 

I have a tendency to think it is the temp sensor as well.. The only way that I have seen engines almost instant overheat is when they crack a head or blow a head gasket. These will both pressurize the cooling system to the point of spewing into the overflow. Also engines with this problem don't typically run well..

 

Usually head gasket doing this.. Sure hope not..

 

Nope, bad idea. You're all wrong.

 

Not meaning to be a dick or anything... But what are you basing your opinion on?

 

Ex mechanic plus lot's of automotive schooling and I had this very problem which threw me a curve because it had a brand new cap and thermo which were both defective. All good for a year now. The modular engines have a unique cooling system that requires a proper thermo and not saying all aftermarket ones won't work but the Mtrcrft one will work properly. If it's failsafing/limping it's not worth messing around with aftermarket. Let's just wait on the report from the O.P.

 

We shall see... I'm a certificated Journeyman Mechanic myself although working in the technology sector now. I respect all opinions when solidly based. The OP's issue may well be from a fickle stat that works some of the time but not all the time, but most stats will either work or fail just due to their design.

Electrical sensors, on the other hand, can work intermittently and with poor solder joints or connections can fluctuate wildly as well as instantly.

 

I have seen all these problems so I am not going to call everyone wrong.
If you get out of the truck and lay your hands around the engine compartment you would know if it is overheating and that is what the OP did. I used to get false positives also.

Oh, and I am a recertified Master ASE Auto Technician that used to teach auto shop but I learn everyday that I do not know enough.

 

Agreed je5 - I'm not done learning either...

Will be interesting to see where this one goes.

 

Actually that failsafe system can fluctuate and it only takes about 220* to set it off so just putting your hands on the valve cover is not an option (been there, done that). Luckily the engine doesn't blast heat in your face, boil the rad, and smell like frying parts before it goes off. I don't mean to be rude by saying everyone is wrong but they are wrong for jumping to the harder to fix and less probable things first. That engine has a recirculating pre-heat system to prevent hot spots and and provide stable heating for the heater etc. The thermo is critical and the double valve thermo needs to be made just right and this is one case where you NEED a Mtrcrft one. Also if the cap is bad it will failsafe before it boils over. Also if it does lose water through the cap it will failsafe more before you add water to it and it will just trickle out leading you to believe it is going out through the heads, etc.
I had to pressure test new caps at the parts store to get a good one (2 bad) and compare the aftermarket thermo next to a Mtrcrft. Believe me; it frustrated me for 3 weeks. $12 invested............done.

 

OK guys,

Thank you all for the tips and insight.

Today I had to drive home with the truck, about 140 miles. It ran fine for the first 40 miles, then the temperature went up as soon as I got over 55mph. I stayed at around 53mph, and the temperature stayed fairly consistent; normal when going downhill or level, slightly elevated when going uphill. Another 10 miles, and suddenly the gauge pegged into the red corner. It did NOT go into limp mode. I pulled over, shut off the engine, waited 5 seconds, turned on the ignition, and the temperature gauge indicated normal temperature. I drove off again, and the gauge stayed at normal for the next 10 miles. Then suddenly it pegged into the red corner. I stopped again, turned off the ignition, waited a few seconds, turned it back on, and the gauge indicated hot red again. I started, and the truck was in limp mode. Turned it back off again, waited a few seconds, back to ignition, and the gauge indicated very slightly elevated. Started the truck, engine ran like a top, looked under the hood, nothing felt hotter than it should, so I drove home. After about 5 miles, gauge pegged red again, I pulled over, let the engine run, checked under the hood again, no elevated temps, so I took the gamble and just drove it home with the gauge pegged red for 50 miles. Truck ran fine the whole way. So I'll go and replace the temp sensor this week and let you know.
Berrie

 

Do yourself a favor and find the harness that plugs into that temp sensor - disconnect & reconnect it.. It may be just a bad connection!

 

And not the cap and thermostat ? Don't do them all at the same time do we will know what it is. Again; it might not seem to be too hot but it is and it won't allow itself to get extremely hot. Don't waste your time and money changing the sensor.