1986 F150 Lariat, 302. All the cooling system is new including the clutch fan. I washed the radiator out real good while I had it out. New thermostat. The truck does fine with the ac off. Any ideals

 

Is the shroud behind your radiator still there? Have you tried driving out on the open road at say 40 MPH or faster with the AC on to see how it acts then?

 

First things first. Beg, borrow, or steal an infrared thermometer. Take a temperature reading at the thermostat housing. Determine if you have an actual overheating issue, or if the indication is acting up.

This thread was never fully resolved, but on the subject vehicle the temperature gauge would climb when the AC was on:

https://www.ford-trucks.com/forums/1...-is-going.html

 

The shroud is all there. I drove it on the interstate and side road at 45 and faster to try to get it cooled down. When I got home I open the hood and it was hot. It was filling the over flow can. I am thinking the air compressor could be going out and putting too much drag on the engine. It looks like it was replaced before I got the truck. It did sit for 10 years in a garage

 

So, what did the temperature gauge show when you were driving 45 and faster? It would not be unusual for the level of the overflow tank to rise after you shut the engine off. In the days before overflow tanks, you had to leave the level of the radiator quite a ways below full or you would end up with a lot of coolant on the ground the first time the engine was warmed up. I'm not necessarily saying you don't have a problem, just sayin. So what did your temperature gauge read at different times?

 

Let me guess. You are looking at the factory gauge to determine the temperature of the engine? Wrong thing to do. Do what the others suggested and get some other way to measure the temp of the engine. Also if it was getting hot, the fan should lock up and there is no guessing as to when the fan locks up, it sounds like a jet airplane under the hood. New parts do not mean good working parts in this day and age.

 

Hi Dave! I've clocked you in at 3 hours and 13 minutes elapsed time. Not your best effort, usually you're under 2 hours. Everything okay? Feeling under the weather?

 

The overflow may be perfectly normal, with the cap operating as designed. When's the last time you opened the hood under similar conditions? When hot, it's not abnormal for some coolant to vent to the overflow canister. As the engine cools, the coolant gets drawn back in. Unless you were consistently watching, it could be happening every time.

I wouldn't worry about excess drag from the compressor. The belt would slip (and squeal) long before dragging down the engine.

The primary heat-generating issue is the hot condenser in front of the radiator. It preheats any cooling air about to pass through the radiator. This in turn taxes the capacity of the cooling system, much like driving through a hot desert.

Once again, I'd suggest getting an infrared thermometer. Measure the temp at the thermostat housing.

Next, measure the inlet and outlet temps at the radiator. You should see at least a 30F drop. If not, figure out why. Could be scale inside the radiator, limiting heat transfer. Could be inadequate airflow. Could be a weak cap venting early, so pressure can't build to the normal range, which reduces cooling ability.

Next, if the thermometer confirms an actual high temperature and not just an indication issue, do a pressure test of the cooling system. Check the cap, too. I'd even suggest checking the seal between the cap and radiator neck, as detailed here:


https://www.ford-trucks.com/forums/1...lant-leak.html

 

Thank you for all the help. I am going to swap out the cooling fan again. Like you said, could be bad new. I put it on last year when I went through the cooling system and I will put a temp guage under the dash and see what happens then. I know not to trust the old one in the dash that was buried when I pulled into the driveway. I have a hand held temp guage that I can get some readings with

 

Just because you flushed the radiator it could have scale built up the you can't see and flushing can't clean.
A radiator shop can flow test it and see if it has scale build up.
Scale build up will stop heat transfer.
Dave ----

 

Do you ever hear the fan clutch kick in? On my truck (351W), it unmistakable. It sounds like a hovercraft under the hood and will rapidly bring down the coolant temperature. It's possible the new one is bad, but there's an important caveat to consider. The rest of the cooling system has to be in good working order. The fan clutch operates by sensing the temperature of airflow leaving the radiator. If not enough heat is transferred to the air (scale inside the radiator acting as an insulator, for one example), the fan clutch never senses it should kick in. So just be aware the poor fan clutch often gets wrongly blamed when the root problem is something else limiting heat transfer.

That's why I've suggested some basic checks of the cooling system, such as measuring the temp drop across the radiator. A system pressure test is important, too. If the system can't hold the design pressure, no amount of parts swapping will fix it. Test the cap's ability to hold pressure, too. If you don't have a pressure tester (we don't judge ), some parts stores have free loaners.



Careful, it sounds like Svengali Dave has you under his sinister stock-gauge-hating spell. The main difference between the factory gauges and the $20 aftermarket gauge set? Numbers painted on the face of the dial. I'm very happy with my stock gauges, and the needle typically rests between the O and R on NORMAL. I don't care what the corresponding number would be, and it doesn't really matter. That spot on the gauge means my cooling system is happy. If I see the needle moving to the right, I know the engine is running hotter than normal and I can take appropriate action.

You may have noticed I love busting Dave's butt about his hatred of the stock gauges. Here at the Stock Gauge Anti-Defamation League (SGADL), we have a team of clinical researchers trying to understand his deep-seated animosity. The prevailing theory involves repressed memories of some kind of childhood trauma about the stock gauges, perhaps involving a trusted family member. Even after years of dedicated research, we must admit the inner workings of the human mind are a mystery.


"Buried"? Huh? As in pegged high? As Ricky Ricardo would say: You've got some 'splaining to do.

Remember, at this point, we still don't know if you're dealing with an actual overheat or simply an indication problem.

 

I put my hand held temp gun on the seat this morning so next time I drive it I can open the hood and aim it at areas and get a reading of the temps and go from there

 

Most of the working clutch fans I have had made a roaring noise every morning during cold start for about 30 seconds or so. Something about the fluid settles out sitting overnight and locks it up till it starts spinning and the fluid gets back to where it belongs.

A radiator guy showed me how to test a radiator to see if it's clogged. You drain the radiator of coolant, take the lower radiator hose off completely, and then get a hose (a bucket will probably require two people) and with the palm of your hand over the lower outlet to plug it off, fill the radiator to the top with water. When it's filled, quickly take your hand off the lower outlet. He said the lower outlet should flow full volume and very smooth and fast. If it struggles and gulps, the radiator is clogged.

 

I ran it until it started getting hot and the laser was going over 200 sitting still. The clutch fan never changed it speed or locked up. swapping it out under warranty in the morning and test again Thanks for the help and I will let you know

 

And why nothing beats a non-clutch fan, nothing to fail
I know my truck with factory AC should have a clutch fan but that I think went with the motor from the parts truck that the HVAC parts came out of.
I did swap over the larger radiator support and had to find a shroud but the direct fan works just fine.

BTW the parts truck AC radiator had white crusty stuff in around the tubes so I used vinegar, cap on and laid down flat, and let it sit a few days and flushed.
Well it did a good job of cleaning it as it had pin holes all over so it got a new radiator.
Dave ----