I've got a mildly built 390 in a '68 F250 Highboy. I do a lot of low speed driving in the summer and was having problems with overheating so I replaced the radiator with a Be Cool radiator and I installed an electric fan - a flex-a-lite high flow "S" type fan.

Now, instead of running 180 degrees on the freeway I'm running at 190 degrees - is that because the fan is limiting air flow? Is this OK - do I need to make an adjustment?

Also, even with the fan I'm still getting to 210 degrees on my worst low speed climb. Is that reasonable? It's a very steep gravel road with a top speed of about 10 miles an hour that's about a mile long. Before the fan I boiled over at the top a couple of times. With the electric fan I don't boil over, but I get pretty close.

I rigged the fan to the battery instead of the ignition so it can run after the truck is turned off - does it make any difference?

Peter

 

Down shift it and keep the engine revs up.

 

how old is your thermostat? Might be failing on you, how about your hoses? they new? The fans probably are limiting some air going down the road, but in slow motion, or stopped they should move enough air to keep the truck around the thermostat temp. what cfm fan did you use ?

 

Thermostat and fan are new. Revving the motor does not seem to help a lot. It's a 2,500 cfm fan.

Peter

 

Is that radiator large enough for your size and hp motor?
Like trans coolsers, rated for how many pounds trailer weight, that's a bunch of crap as you want how many BTU's it will remove.
Bears on the right track but only with a water pump mounted fan, I run a stainless flex fan with a shroud. In stop and go traffic, heat with a tail wind the temp goes up until a 1,500 rpm idle for the fan to pull more air then the temp drops to a solid 185 degrees. This is with a 180 stat.
Stainless flex fans will flatten out restricting flow at highway speeds but this is only a small amount.
.....=o&o>.....

 

Not just the fan, but circulating the coolant thru the engine and radiator. Lugging an engine under heavy load is a no-no as it builds excessive heat and does not move coolant at a rate to remove that heat. Besides it alway better to tow with a few extra revs. The lugging thing is shown with the recommendation of the newer overdrive units that say "Do not tow in Overdrive". I am alway manually down shifting my autos when towing (I only tow with autos anymore), for better preformance and to prevent overheating.

 

Isn't there something about the vac advance inside the distributor not working that can cause an engine to run hot ? I don't recall if the bad vac advance sticks totally retarded or totally advanced but that condition can cause your cooling problems.

Can someone with a better memory confirm which condition it is ? too much advance all the time or zero advance all the time ?

 

Make sure your thermostat is also a good quality one; I've had a couple of offshore units that were bunk, out of the box. Motorcraft is always a good choice.

A lot of vehicles with electric fans are set up that way. Also, if the cooling system is getting ready to let the steam out, (most likely to happen immediately after shutting down a hot engine) letting it idle for a minute or two (or until the fan stops) after the work has stopped will reduce likelihood of that happening.

 

Sticking at full vacuum advance will cause overheating. Not working at all shouldn't unless you have too much total mechanical and initial cranked in, like 38°, which will be fine for short drag races but can kill you when towing. I don't run more than 34° total and usually 32° when towing or carrying the camper. A total of 36° to 38° seems to push the temp above 200 and I don't like that, even if it is technically a safe temp.

 

For those finding this thread in the archive looking for overheating and electric fans here's what I figured out.

Once you install an electric fan with integral shroud like the flex-a-lite 180 normal air flow through the radiator will no longer cool the engine effectively. That is, where on a car with an engine mounted fan you get get on the freeway to cool off if your engine gets hot that won't work with an electic fan with shroud. The fan is too much of an impediment to air flow.

So, you can't set the electric fan to come on as a "backup" at a higher temp. Your truck is now going to run at the temp setting on the electric fan.

And that seems simple enough, but it took me about a week to get it right. The temp gauge in the cab shows manifold temperature and the fan is sensing radiator temperature and apparently they are not as close to eachother as you might think. I kept thinking I was setting the fan to abou 185 degrees only to figure out on the road that it is really set over 200 degrees. So I went to the braile method. I set it completely cold and then raised it a step at a time between trips until I had it right were I wanted it and now it's working great.

The setup I ended up with is a Be Cool aluminum radiator (which turned out not to be square which was a bit of an installation issue), Flex-a-lite 180 3,300 CFM fan with controller (which installed very easily) and a new Milodon high flow thermostat (which looks and performs exactly the same as the stock thermostat from my FLAP).