Okay, here it goes. I have a 1999 Ford F250 super duty extended cab utility bed work truck with a V10 motor. It’s always ran cool. But yesterday it overheated when I was on the freeway (the temperature needle was in the red) and the only reason I noticed is the truck lost power. I was able to pull off the freeway and coast though a couple of lights and park near the mall in Bakersfield. It’s harder than hell th turn the steering wheel when the motor’s not running. It was 103 degrees that day. The water had shot out of the plastic radiator cap though the pressure relief. Waited for it to cool and removed the water neck and threw away the thermostat. Filled it up with water and ran it at idle for a while. Drove for about 5 miles in stop and go traffic and all of a sudden the gauge goes from cool to hot (almost in the red again). Pulled over, waited 30 minutes for it to cool a little. Poured the bucket of water I filled up from last time into the reservoir, ran it for a few minutes and took off again. The stupid thing over heated five times that day, usually around my next stop-I’m an AC guy. Here is where I’m at now. I have no leaks, waited for the water to drip from somewhere after driving it home and filling it up. All week end I waited for it to leak, started it every couple of hours and let it run at idle. Water pump is solid and I can see the water running through the clear reservoir connected to the radiator. Fan is always spinning and fan clutch always works. Finally, thinking I blew a head gasket, I did a head gasket leak test expecting fluid to turn from blue to yellow indicating a blown head gasket. And the stupid fluid stayed blue. Oil also looks fine and I pulled the radiator out to see if it looks clogged and it’s not. Almost bummed out because thought for sure the head gasket would be the problem and I could have someone fix it. Is there anything I am missing that’s not so obvious? And thanks for any advice.

 

Sounds like you've done the obvious with thermostat, water pump, radiator, pressure test etc.
Not that it would be the issue if it overheated again after a few minutes but there's lots of comments about the poor coolant reservoir caps not holding appropriate pressure.
Ever used stop leak products? They've been known to obstruct coolant lines if overused.

 

Are you running a motorcraft thermostat? Aftermarket have been known to cause issues.

 

Put a new radiator cap on last night and drove it for about 20 miles and it seemed good, water temperature a little low because I haven’t replaced the thermostat. Drove it all day with no problems then towards the end of the day I drove up a steep grade 3 miles long and the temperature gauge climbed all the way up to the red line. I pulled over and let it idle and it went back to the normal position in about 5 minutes. Also, I’ve never added any stop leak products. Thinking about removing the water pump just to look at the impeller, maybe a piece broke off the impeller and is caught somewhere in the cooling system and causing a blockage.

BTW, thanks for all the replies.

 

can you tell if the fan clutch is engaging?

usually if they are working, you should hear the fan "roar" for the first minute or so after a cold start in the morning regardless of the temperature outside. it should be very noticeable when it releases shortly after taking off from a cold start.

it is also possible that your water pump is working, just not properly.

too, although it is counterintuitive, running with the thermostat removed can also cause an overheat condition. without the restriction in the system that the thermostat provides, water flows too quickly through the system and does not allow the radiator to do its job. that is to say, the water flows across the radiator quicker than the cooling fins can remove the heat.

getting hot while going up hill is a clue for sure, just a matter of figuring out what that is telling you compared to what you already know.

just a couple thoughts.

 

Still having problems and haven't had time to post, air conditioning work until midnight just to get ready for next day - It's pretty hot in Bakersfield right now. Anyway I'm so busy I don't have time to take the truck in to someone and thought I could fix this a night when I am getting ready for next day. As I drive around the truck randomly overheats. It will quickly go from normal temperature, about 3/8 of an inch above the bottom reference mark of the temperature gauge to just below the red in less than a minute. Sometimes once a day and other times 3 times a day. I can drive 10 miles and no problem, other times maybe just a couple of miles than, bam, it's over heating. Changed the fan clutch out today around noon and drove for 8 miles and it started to overheat again. Most of the time I see it start to overheat I pull over and put the truck in park with motor running. It will cool down into normal range in 2 to 5 minutes. I take back off and sometimes it starts to heat up, other times it will be fine for next two to three stops. The over heating is completely random. Sometimes it happens on the freeway and other times on surface streets. Today when it over heated I pulled over to let it idle in park and it would not cool down. Just stayed right below the red reference point on temperature gauge. So, new water pump, fan clutch, thermostat, and radiator cap and same problem. Going to compression test next but thought exhaust gas test in radiator covered that? Time for new truck. Anybody ever drove a dual fuel CNG/gas vehicle? Sort of thinking about it.

 

What about the radiator itself? I've seen the cores restricted with muck that would not allow good flow. A temperature gun reading across the cores may help diagnose. I have also had a delaminating radiator hose running in circles for a while also. Ultimately the only way I found that was when it collapsed altogether.

Good luck!

Regards - Randy

 

I would consider replacing the thermostat and doing a back flush on the cooling system.

 

Have you considered a new water pump at this point?

 

Did this issue ever get resolved? I started to have the same issue.