Hrmmm...interesting. That sort of implies that it's not a sensor issue at all. How well has the system been maintained? From the factory your truck came with antifreeze that needs to be replaced every 30,000 miles. Do you know if it was maintained?

The fact that the temperature came down when you turned the heat on implies that your radiator isn't working very effectively. I'm thinking you may have a blockage of some flavor.

 

Does it hold pressure for 24 hours+? Did you buy a cap?

 

Tom,

I think you are right. I've had the truck for 4 years, but as a secondary vehicle (and because it is mighty thirsty) I have only put the last 15k of the 185k miles on it. I haven't flushed the cooling system. Just checked the radiator for bugs and leaves.

So most descriptions on flushing are to drain current liquid, fill with radiator flush, run until normal temperature, then 10 more minutes, drain again, and fill with coolant. Is that sufficient? If there is a blockage, wouldn't it be better to disconnect both radiator hoses and press water through the radiator in the opposite direction?
How much coolant will it take?

Brent, I ave not yet purchased another radiator cap. If flushing doesn't help, that will be the next step. I mean, flushing needs to be done anyway, so I'll do that first.

Thank you all for your patience and sharing your experiences with me.

Berrie

 

I assumed that was already done but do my flushing technique, it works very well.
https://www.ford-trucks.com/forums/1...al+clear+water

and read this:
https://www.ford-trucks.com/forums/1...al+clear+water

 

The exchange quoted above has me wondering how many people have a system like Brent does, a system that will hold pressure for 20+ hours after an engine has been shut off after it has reached operating temp.

I just got back from towing my travel-trailer back from Yosemite. We pulled into town around 4pm yesterday, unloaded the trailer, and I then went and filled the tank with diesel. After fueling the rig, I towed the trailer back to the storage place and came home. My son then borrowed it to go to work as a bouncer at a sports bar 30 minutes away. He gets home around 3am in the morning, about 8hrs ago.

I'm gonna go out and check my system and see if it hisses.

Stewart

 

I've opened my radiator caps and degas bottle caps many times over the years on my non-Ford products and I can't remember a hiss 24hrs later, but in checking the Ex just now, there was a small, quiet hiss.

So I then checked my F250, which has been sitting overnight longer (since around 8pm last night) and it had a bit louder of a hiss when the system released pressure.

Stewart

 

OP, my symptoms were similar to yours. If I drove slow it wouldn't overheat and peg but if I drove too fast it would peg. I already posted a thread above about what I went through. But, like you, I thought it was things other than the CHT.

Mine pointed to a coolant flow issue. But after replacing every part of the cooling system - which I did as a preventative maintenance issues figuring ONE of these items would work. If it's a partially clogged radiator, a weak hose that is collapsing or whatever, I didn't want to deal with chasing any of that down now or in the near future. I replaced it all.

The problem did NOT go away. It was only when I replaced the CHT that the issues stopped. Now...could one argue that it was the CHT in conjunction with another issues? Sure... But I noticed no difference after changing all of that out - it performed exactly the same.

I won't speak about what the issue was for others - I only know what worked on my truck. As I stated before the CHT can be removed after pulling out the alternator. It's easy to find but not easy to reach. So, you will need to sacrifice a wrench by heating it up and smacking it to bend it (or put in a vice or whatever). I think i bent mine back after I was done.

I believe it's a 3/4" or 19mm and I think I used a box end wrench. Good luck, I know how frustrating it can be!

 

But wasn't one of those changes done at or near the same time you changed the head temperature sensor? (cht)

 

Brent,

Please stop. I made it perfectly clear in an early post (#48 to be exact) the sequence I went through. Thermo first, it didn't work. Next was radiator, hoses, water pump, clutch fan, etc. Still did not work. I finally gave in and changed the CHT. Voila.

Btw, OP, I did leave out one detail. I put aftermarket gauges (Phantom II's) in the truck after I changed the thermostat b/c I'd read how the factory gauges are glorified dummy lights. This let me know that the truck was running "warm" but no where near overheating (210-215 degrees max). This was the item that let me know the gauge in the dash was just plain wrong - that it was getting bad information from somewhere.

In my case - it was the CHT.

I also installed a double-capacity radiator when I did the change - best upgrade I could have done to the cooling system!! Highly recommend! Truck ran at 190 all day after that - no matter the temp, what I was hauling, how steep the hills I was climbing. 190 awesome degrees, LOL!!

Let us know what you find!

 

Could be a lot of things, I'm surprised he hasn't changed the cap by now though........and where is he?

 

OK Guys,

I did the extended radiator flush, and then refilled it with fresh coolant (all 4 gallons), and I drove it for two days to work. Each way 20 miles, most of it at 60+mph. No overheating!

Now, to be fair, it was 10 degrees cooler than usual on both days, but I did drive it pretty hard in the afternoon, and it didn't overheat.

As I was removed the radiator cap 14 hours after running it, there was a hiss, so the radiator cap is good.

I will run it again after next weekend when we will have temperatures in the high 90's/low 100's again. Once I know it is fixed, I will report back in, and bring my other Ford (Crown Vic) to the shop to have the transmission rebuild.... (ouch)

Thank you all for your insights!
Berrie

 

Waiting to hear the verdict.

 

I too had "False overheating", Gauge would suddenly peg, limp in mode would be activated. No boil over, temp laser reading around 220 top of heads, 190 into rad, 120 coming out. Messed around with sending units, nada. bought a motocraft tstat just to try it, ended up pulling the water pump just for giggles. ALL THE VANES WERE GONE!

 

Was it from foreign material or lack of antifreeze over the years?

 

That was a while back, he lost his pump vanes somehow.