Friggin truck.

Has it got a manual thermostat? That is, an aftermarket one?

That is, be SURE of the temp, before trying to solve this one.

I have seen BAD and sticking thermostats, do pretty close to this.

N

Had a plymouth that had a bad oxygen sensor that would fail after the engine got good and hot, It would start running rough and then quit altogether, wait till it cooled down, and do the same thing all over.

The thing is, once it is running bad we cannot get the computer to communicate with the reader.
Once it cools off it will then communicate with the reader.

Nate, the thermostat is good to go.

Sounds like a leaking head gasket. I had a similar problem once and by the time I figured it out the engine was shot from the coolant getting into the cylinders. might be worth getting that checked at the shop.

Does your truck have a DuraSpark II system? You might have a break in the 'resistor' wire that opens when it gets hot.

D7AZ-12250-A Resistor, Ignition Coil-49" length (Motorcraft DY-213)

DDSM
(Is not a mechanic)

You didn't state the obvious? Did the truck really overheat the last time it broke down? It shouldn't run rough or boil over until you are above 240F.

210 degrees wouldn't be running hot. I'm going to assume you've looked at things like plug wires, spark plugs, and all the other wiring that might be related to the computer or ignition. Open the hood up at night and see if you can see any arcing. There are so many things it could be, its all a matter of guessing at this point.

Even after it cools down, the computer should have stored a code if there was anything it had complained about.

Vapor lock?

Irritating when old reliable stops working.

Maybe your temperature gauge or sending unit is broke.

A big question is how many miles on your engine.

Some will make hundreds of thousands and still run fine and others will not.

No matter how good you like the vehicle you have, at some time you must decide if you want to continue to fix a lot of small problems or just start over and go with all new under the hood or all new including the hood.

A few years ago I put in a new engine and accessories in an 89 F150 and rebuilt everything else in the drive trane, mounts, bushings, brakes and bearings.

Now it's still my old favorite truck and it works and drives like new, but cost less.

good luck

If the coil is good, I would check the fuel pump next.

> So far I have replaced the radiator, fan clutch, thermostat, ignition control module, distributor and I am about to replace the computer.

> Really starting to get tired of this.

This is why I have a good, reliable mechanic.

I am a good surveyor, but a lousy mechanic.

I used to think I could save some money by doing it all myself. Always drove late model trucks because I thought they were easy to work on. I'd change every part I could think of, bust bolts and knuckles, and waste hours of my time and money, getting greasy dirty, lying under my truck in the cold rain in the driveway.....

Good luck my friend 😉

Dugger

I bet a 25 pound Blue Crab crawled up your muffler.;-)

Blown headgasket will make the engine run hot. One or both of two things should be happening with that scenario:

1) Steam coming out of the exhaust.
2) Bubbles in the coolant recovery tank when you rev the engine and a smell of unburnt fuel in the coolant recovery tank. Simply put if a headgasket is leaking water into a cylinder it is also getting unburnt fuel mixture in the coolant when that cylinder goes on the compression stroke hence the smell and bubbles in the coolant recovery tank.

Other things:

Rocky laying down on the job and mice/rats munching on your wiring harness creating a short.

Remove and clean all the ground wires you can find.

Good Luck.

It is not running hot anymore and the only time it runs bad is when the air temperature outside gets above 93.
I got on the interstate yesterday morning and got it to 80mph with no problems, temperature never got above 195.

Load a burlap oyster sack with ice and put it near the engine air intake when it approaches 93F air temp. That might rule out the electronics in that area?

Knock out the freeze plugs and give the block a good flushing before replacing them. Also take the thermostat out and stick it on the stove in a pan of water, use a cooking thermometer and see if it opens and closes when it should. New ones have been known to stick.
jud

Sounds like you need a mechanic. That is where they pay off.

Simply replacing parts and hoping it fixes the problem usually costs much more. Hopefully the radiator was rotten and leaking, the clutch fan was slipping when it was hot or froze up, the thermostat was stuck open or not opening at the proper temperature, and the entire distributor was completely shot. Been there done that.

I know it's computer controlled, which adds to the problem. I always look at it in a simplistic view like a lawn mower. When it shuts down and will not run, are you lacking A:Fuel or B:ignition? It's usually one or the other with truly older trucks, however with a computer controlled engine, it may be shutting off both the fuel & ignition. Why would it do this?

When throwing parts at a problem like you describe, I have replaced the O2 sensor and the anti-knock sensor. Each time I was simply throwing money away.

JRL

A truck I had, about 20 years ago, did that exact same thing. The "computer" had gone bad. Replaced it and no more problem.

He could also upgrade to a 67 model, new is not always better. After the big boom and radiation burst, with that 67 he could still drive around, might need to build a producer gas system and burn wood scraps. Kind of like making charcoal, that is what is left after all of the volatiles are cooked off.
jud