Hello everyone,
Im new here. My dad picked up a 1984 F250 5.8L that only had 35,000 original miles. The truck sat for at least 2 years, he replaced the clutch fan, thermostat, water heater, radiator cap, new spark plugs and wires along with some other regular maintenance items. The truck overheats when driven over 65 mph and in hot weather. When it was cloudy and my dad was driving the truck from Denver to Nebraska he had no issues, but on his way back it was sunny and hot and it overheated. My dad is a mechanic but does not know what else this could be. He does not think its the head gaskets as it does not overheat when drives under 65mph. Anyone have any ideas???
Paul

 

Check that the lower radiator hose has a metal spring inside the hose. If that is there, then open the radiator cap and look in the radiator. If you see a bunch of white stuff, the radiator may be clogged.

Overheating on the highway is generally a coolant flow problem. Overheating in town is generally a air flow problem through the radiator.

 

Hey Franklin,
Thanks for the response. Dad said he has the spring in the bottom hose. He also said that he didn't see any white stuff..
He did ask however, if the top radiator hose should be empty, because it seems as though his is. Also, is there an overflow reservoir? He said that his truck does not have one.

P

 

I had a blown head gasket and the thing would do fine in town or on a cool day, but above 45 or 50 it would overheat on hot days.

The overflow bottle was dual purpose and held the windshield washer fluid as well. You can substitute any kind of container for it.

 

How do you know it was over heating? Did it boil over or are you just going by the gauge?

On my '87 E350 the gauges run off an instrument cluster voltage regulator (ICVR) and they can be pretty screwy. On mine if I ran the headlights and blower motor for the heating and AC the temp gauge would read much higher. I tried another ICVR and it's a little better but still not right. On my list is installing an aftermarket temp gauge...

Taking a reading at the thermostat housing with a point and shoot infrared thermometer will at least give you some accurate data and tell you if you are indeed overheating or if its just the gauge.

 

I had similar thoughts, but assumed a mechanic would know. However, I thought another of mine was overheating and it was the gauge. I, too, installed aftermarket gauges.

Brnfree - Go to my album on How To Make An ICVR Replacement for a cheap and accurate ICVR.

 

Its definitely overheating. He said that the radiator cap is spitting coolant. So does anyone know if that top radiator hose should be empty?

 

It should not be empty. With most of the air out of the system, which may be the problem, the top hose should have water in it, even if the engine is cold. However, it won't be hard at that point as there is always a bit of air in the system. It will be hard when the engine is up to temp as the system will be under pressure.

So, he has to get all of the air out, which may require bleeding it out at the temp sending unit. Then he should monitor it for coolant loss and if it is losing coolant, as I suspect, he has to find out where it is going.

But, it is possible the radiator is so plugged up that it won't cool the engine on a warm day. If that is the case he may be able to clean it some by backflushing it.

 

Also, it is possible to get a bad radiator cap NIB. I would try another one for the price. I had a bad one and it kept pushing coolant out no matter what I did. A good new one fixed it.

 

I was going to say, just because it's spitting out fluid from the cap doesn't mean it's overheating. You really need a good aftermarket guage on it to be sure what's going on.

Take the cap off when it's cold, and pull the rubber back with a small screwdriver(the rubber near the top of the cap) and see if the brass piece up in there has any cracks. That will cause it to spit coolant for no reason.

Also, what lb cap is he running on this truck? With no overflow bottle hooked up, you can't fill the radiator to the top. If it has a 13 lb cap or higher, then you can run the coolant up to a 1 inch or so from the top, but you have to leave a air space, or it will create it's own by puking the coolant out. If you have a 7 lb cap, you need to leave a lot of air space in the top of the radiator.

Other signs that it really is overheating; It's pinging and knocking when it's hot, you can smell oil on the engine getting hot, and it idles rough from the fuel in the carb boiling.

 

The water flows from the top of the engine, into the radiator (at the top), through the radiator and back into the engine at the bottom.

I wonder if your thermostat is stuck or sumthin'....

 

I thought I would let everyone know that it was indeed a clogged radiator. My dad replaced the radiator and the truck runs great.
Thanks to everyone for your input.

 

Glad you got it sorted. Those problems aren't fun.