1984 F250, 300 cud 4 on the floor. Took the truck to emissions yesterday and it overheated. This is the first time I have run it that long. Truck has not run in a lot of years. I have a new 4 row radiator, new 160 thermostat, all new hoses, engine is in time.
Does anyone have any ideas? The water pump is not leaking so I am assuming that it is good.

 

Were you sitting still / moving very slowly at the time? Or moving at a good clip, say above 30 MPH? Airflow through the radiator is a huge factor for cooling. If cooling is okay above 30 MPH (lots of ram airflow), suspect insufficient airflow from the fan when moving slowly or stopped.

Does your radiator have a shroud? That's another huge factor for adequate airflow at lower vehicle speeds.

 

I have to ask, how do you know it's overheating? What were the symptoms? We have had some interesting answers to this question before.

 

I like what Karl posted of the speed & over heating.

Question, when you replaced the lower hose did it have a spring inside and if not (most if not all new hoses do not) did you take the spring from the old hose and install it in the new one?
If missing this can show up as over heating at speed / higher RPM as the water pump sucks the lower hose closed and not coolant will flow.

What was the coolant level?
And how did you know it over heated? Did it puke coolant on the ground or the factory gauge said it was?

If the truck has / had AC or think HD cooling it should have a shroud other wise it was just a cover over the top of the fan to keep fingers out of it.
Dave ----

 

Truck was sitting still. It is not registered so cant really drive it on the street. Temperature gauge was all the way at the top when shut off and blew a lot of the antifreeze out

 

Truck does not have a shroud just a little thing on top to keep you from putting your fingers into the fan. Coolant was full.. Does not have A/C

 

The original radiator had only two rows and the new has 4. I did not put the spring back in,

 

Radiator cap not holding pressure? No pressure drops the boiling point. Good cap and good 50/50 mix of coolant and you'd be good to 250°F.

 

Dave mentioned non-AC trucks didn't have a shroud. I have NO idea why Ford omitted the shroud on those models, as cooling airflow through the radiator is still very important.

Note I said "through" the radiator, as opposed to air swirling around next to the radiator. A fan without a shroud will pull some air through the radiator, but not much. To test for adequate airflow, briefly run the engine at idle and hold a rag or sheet of paper in front of the radiator. It should be held tightly in place. Only do this test with the engine cold to reduce the risk of overheating.

One possibility is your new 4-row radiator is too thick compared to stock. The original was probably some skinny little thing and the unshrouded fan was able to draw enough air through it. But now you've changed the equation with a thick radiator that creates more restriction to airflow through the core. If that is the case, I'm not sure what the fix would be. Maybe go back to a skinny stock radiator or add a shroud.

Another possibility is your new thermostat is bad from stock and staying closed. I have had several bad thermostats in the last few years, different brands on different vehicles. It's so frustrating, and I have learned the hard way to test a new thermostat before installation (Submerge in a pot of water on the stove). You can test your present thermostat with one of those infrared thermometer guns. Measure the temperature where the upper radiator hose leaves the engine block, just downstream of the thermostat. If stuck closed, you will see the temperature there significantly cooler than the rated 160F.

 

Oh, there you go. That could be at least part of the equation.

 

At idle I cant see this as the cause because the RPM is not up that high to close the hose off but I would install one so it would not happen.

I do like the new stat being bad as the cause.
Could pull it and test as Karl said. If you have the old one I would test it also just for S&G.
Before installing a tested good stat I drill a 1/8" hole in the flat part and when installing it put the hole to the top.
This will let air through to help in burping the system.
Could it have been that air was trapped before the stat so hot water never hit the stat to open it?
The drilled hole will help in that case.
When I refill a system I keep the cap off and let the stat open a few times, show some temp on the gauge if it has one before topping off and putting the cap back on.

As for to thick of a core well I guess it could be and more so with out a shroud so do the test as Karl posted and see what happens.
Now being you dont have AC you would have a smaller core radiator and I dont think Ford used a shroud on that size radiator.
The AC radiator has a larger core so its shroud I dont think will work.

Measure your core and I can measure mine and see if the shroud I am using would work.
I will let you know there are 2 different shrouds used for our trucks and LMC needs the number off the shroud to order the right one.
I did not have a shroud for this number so I did a lot of searching and measuring and found one this was the right size for the core and cheap so if I had to "mod it" and did not work I was not out a lot of money. Turned out I just needed to trim a 1/4" off the front side to the radiator for it to sit flush and it bolted right up and works great.
Dave ----

 

Oh as for running with out a stat this could also lead to over heating.
I was told when back in school that the coolant can flow to fast through the system to:
1= not spend time to pick up heat from the motor
2= not spend time in the radiator to get rid of the heat.
So not running a stat is not the answer either.

For racing they make large washers with different size center holes to replace the stat.
You try different ones till you find the right size hole to keep the coolant temp you want.
Dave ----

 

You mentioned you just did some work replacing the radiator and thermostat. Did you burp the system after all this work and got all the air out? It will normally overlflow and run hot till the air gets out of the system. That is why someone mentioned drilling the hole, though taking one of the heater core hoses off while filling will not get all the air out, but most of it.

Now that is did it's thing, and overheated, with it cool take the cap off, it should be lacking a lot of coolant. Fill it just to the top of the radiator core, and leave the cap off. Start it and run it, let it sit till the coolant starts flowing through the radiator, and the upper radiator hose is hot. If it still has air in it, it might overlfow again some. It should finally stop doing that, and once the upper radiator hose is hot, you can top off the radiator level and take it for a drive.

 

This is not likely, but I've seen it happen.......

Fans, fan clutches & water pumps for earlier engines (pre-serpentine belt) rotated clockwise when viewed from the front of the truck & were designed accordingly. On serpentine-belt engines, these parts revolve in the opposite direction & are made to suit. Mixed or incorrect parts will cause an overheat.

If for instance, the wrong fan is installed it will be trying to push air forwards through the radiator, against natural airflow when you are driving. Or the wrong pump won't circulate water properly, & the wrong clutch won't drive/release the fan properly.

 

UPDATE
I topped off the radiator, put the right amount of coolant on the reservoir. started the motor and ran it until it got warm. Put a sheet of 8 1/2 x 11 paper in front of radiator and it stuck there. Truck is running with out the cap on the rad. I looked in the filler neck and can see coolant running through the top set of tubs. Put cap on and continued to run at a accelerated amount of rpms. The temp gauge continues to rise. At the top of the operating range I let off accelerator and checked the bottom rad hose and it is NOT collapsed. The over flow bottle is being emptied. I refiled the reservoir to the low line and used a hose to cool down the radiator. with the temp gauge on the middle of the operating zone I turned off the truck.
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