I will start at the beginning. I bought a 77 F250 about a year ago. Initially it had a valid overheating problem. Understandable, as the fan clutch and thermostat were bad and it was missing the radiator shroud. I also had the radiator cleaned which it did not need, and checked the water pump. I thought I still had an overheating problem as the temp gauge would head rapidly to the right shortly after reaching normal temp. At this point I discovered it was no longer actually overheating.

I went to an electric fan and a mechanical temp gauge so I would have a better idea if what the temp actually was. The new gauge does the same thing. The funny thing is, it usually exhibits this behavior when starting up from cold, although it sometimes occurs when temp is stable and driving down a level road. I have towed a 5k load up a steep hill with no issues. I have taken the temp probe out and refilled coolant until it started to come out the port hoping to eliminate any air pockets. The problem remains. Any ideas?

 

My title went whacky also- I am jinxed!

 

Your work and trouble shooting sure is in the right direction. Getting everything "up to snuff", making sure the air is out and installing the mechanical gauge really helps. ... But the problem persists. OK most of the time even under load but temperature spikes from time to time.

One thing to check is any stress or binding in the T stat. Is the "groove" clean? Water neck in good serviceable condition? T stat installed first then gasket (most models)? The T stat itself could be bad also. I seem to have the best luck with the better parts store brands.

Which engine? 351m/400 need a specific T stat. Make, year, model, engine will get a good one at NAPA. 351m/400 is usually special order in a few days.

Other things to check. Its a long shot but sometimes a lower hose without spring installed can get sucked shut and cause overheating. Newer hoses don't usually have or need a spring. To add one for trouble shooting, buy a corrugated universal hose with spring, pull the spring and install in your hose. Or just get a new lower hose.

Also, there is some chance there is still air in the system. Most T stats have a little bleed valve. If yours doesn't a 1/8" (max) hole in the T stat flange will help with bleeding.

Good luck!

 

Thanks blue and white - I am running a 180 tstat from NAPA, I had a 195 previously, the problem seemed to be a bit worse. Indications seem to point in that direction. Ironically I was in NAPA yesterday when a customer was looking for a hose with wire (not available). It did not occur to me that I should check mine closer than I have.

I'll also check the temp at the housing again and at the manifold by the temp bulb. I will report back.

 

Rather late in reporting back, just wanted to be sure the problem was gone. Have driven the truck extensively, and the temp issue got better and better, and is now gone. I had similar problem with another truck whereby the thermostat was slow in responding, but eventually got "broken in"and the temp stabilized.

I will put this issue to the test when I tow a 10,000# load from NY to TN this coming week. Wish me luck.

 

We made it to TN with no issues other than vapor lock after sitting at a traffic light too long several times. Most of the time it resulted in a stumble, but it died completely in traffic once, blocking two lanes (there were three). A very understanding cop helped me out and was willing to give me a few mins to let it cool off, which worked. My load ended up being closer to 9000# than 10000. I love my truck and the 460 under the hood!

 

Sounds great. Mine has stumbled after hot stops also when towing. Time for an auxiliary electric fuel pump? Or EFI?