First post. First time Ford owner. I purchased a used 2012 Ford Transit Connect with 122k miles from a tow yard (was one of their fleet vehicles) a few weeks back and when I drove it home on a dead battery it was fine for 35 miles and the temp gauge would slightly go above the halfway mark. So I get it home and change the battery, thermostat, waterpump, oil, spark plugs, coolant resivor cap and add fresh coolant. I burped the cooling system to best of my knowledge. The Transit would heat up normal while idling but as soon as I start driving it the temp gauge goes up to 250° F. When I come back from driving it the temp gauge will go from 220°F to 250°F just sitting there. I took it to Ford and they told me the coolant was at 140°F and the cylinder head was at 250°F and they recommended a new CHT sensor and pigtail which I had replaced as well. So I bought a coolant vacuum filler thinking there is an airlock somewhere in the head. I drained and flushed the cooling system and vacuum filled the cooling system and its still doing the same thing but now idles at 195°F and I can drive it around but once I come to a stop again the temp gauge jumps to 230°F then all the way up to 250°F. I've taken it to Ford and had several people look at it and they are stumped just as much as I am.
I have also checked the cooling fans for operation and both low speed and high speed fans turn on. The previous owner changed the radiator and cooling fans.
CEL pops up P1299 CHT over heating.
I'm not ruling out a blown head gasket or cracked head. I also did a compression test and all cylinders were at or around 170 psi.
Thanks in advance for any suggestions.

 

I am not much of a mechanic, but I'm always hopeful. I would be tempted to try another thermostat. The problem sounds thermostatic and parts today tend to be iffy. Also, did you change the radiator hoses?


In any event, good luck with this problem and I hope it turns out to be something easy.

 

The engine + dash harness (Ford part# 12A-581) at the PCM plug has a short. I moved the wires around to see if that's where a short is and the temp gauge went right up to 253°F and would jump all over the place while moving the harness. Ford makes this and stocks it at my local Ford dealer for $118. If anyone else had this problem maybe this post will help.

 

That's good news. Thank you for taking the time to work it out and share the information. Your diagnosis could save someone a great deal of money.