Hi,
Hope someone can help with this.

I have a 1994 F150 two wheel drive with a 5.0L motor.

It also has a towing package upgrade with a larger four row radiator.
The standard was a two row radiator.


I recently changed the timing chain, cover, and water pump so the current water pump is under a year old.


I was overheating last fall on warm days so I changed out the thermostat (went from a 180 to a 160 degree) and a new radiator cap. that seemed to do the trick but no more hot weather until last week.


As soon as the temp got over 90 degrees ( I live in the Southern California desert climate) I started running hot, not bad enough to cause damage but real close. When I stopped the vehicle water was overfilling the overflow bottle and out on to the ground.


I am the original owner since day one and have never skimped on the proper maintenance and this is a new problem.


I have checked the fan clutch It seems to be working properly but this seems to be subjective depending on who you ask. It is not frozen or binding, it does turn smoothly.
I have tested for a blown head gasket, no problems their.
I have also verified their is a spring in the lower radiator hose.
I have not done a flow test on the radiator as it shows no signs of corrosion and I have always run proper coolant.
The heater core is five years old and working fine.
A month ago I did a complete tune up, plugs wires, cap, rotor etc.
The truck has 200,000 miles and runs as strong as ever (except for the slight loss of power when the engine is running very hot).


What am I missing?
Can someone please suggest any other causes I have missed?
Any advice is greatly appreciated.
Thank you.

 

Could it be air in the cooling system? I changed my radiator and heater core out a couple of years ago and I had air in the system that was not allowing the antifreeze to flow properly and causing the temp gauge to go all the way to "L" on normal. I ended up taking the thermostat out and filled the system through the upper radiator hose with the cap off to vent the air. Once I got the block filled with antifreeze, I put the thermostat back in and filled the rest of the system through the radiator.

It may be a goofy way to do it, but I was frustrated and couldn't think of any other way to ensure that the block was filled with fluid, and not air and it has worked perfectly ever since. The temp gauge rarely gets above the "N" now.

 

What brand of thermostat are you running?

Store brand is JUNK! I only opt for Motorcraft t-stats.

Also, if your driving down the interstate, and the vehicle is over heating, that is either a stuck/sticking t-stats or clogged radiator. There is sufficient airflow driving to keep the engine cool, the exception is towing.

I always test the t-stats before installing and never buy Stant or any other except for Motorcraft.

 

Hey guys thanks for the advice


Store band thermostat, however I tested both the 180 I removed and the 160 I installed so I think I'm OK their.


I never gave any thought to air in the cooling system.
Can air in the cooling system cause a problem after several months?
I would have assumed after that amount of time any air would have either caused a problem right away or worked its way out of the system by now.


But I will give your recommendation a try and fill through the upper radiator hose and I will let you know.


Thanks again for the insight.

 

Didn't realize you had problems a long time with this. My bad.

 

I would think after all this time your system has purged all the air...I'm going to bet you have a bad T-stat. My son just went through this with his truck...told him to get one from the dealer. He didn't have anymore problems until he snapped a blade off of radiator fan. That's another thing to look at...he gad always been running on the warm side but since installing the new fan he runs cold. If the fans wore out the blades could be flattening out.

 

Had a similar issue with my 94 f150 5.8. Timing cover leak. Temps would fluctuate erratically for me. Checked everything like you did. Finally took it in to a mechanic who found a small leak on timing cover. heat from motor would always cook off the fluid so I never saw it.

 

If the fan clutch turns smooth that is your problem. Ford has had a history of fan clutch issues from my experience. Rebuilt no good, store brands junk. Buy Motorcraft.
Your fan clutch when cold should be stiff hard to turn. You should be able hear it engage when it comes on. With a 5.0 you should feel it also. I have a 5.0 in a 95 F150 4x4 5 speed.

 

Are you sure your engine is over heating? What does the "i temp gauge say?

Make sure you have the correct radiator cap PSI rating. I once got a 13psi cap and had the overflow tank running over and though the engine was over heating too. Put in a 16PSI cap and no more issues.

By the way, running a 160 t-stat in a EFI engine will cause issues of rich running engine and codes/CEL light light up as the engine doesn't get to the ECU defined operating temp.

 

Kaduh you are the man!!!
I drained the coolant and filled as you advised and for a week of 97 degree weather the truck runs at normal, never overheating. So it seems it was air in the system.
Thanks to everyone for all the good advice.

 

Per what Eddiec1564 says. Also, you need to install a 190 or 195 degree thermostat. Our trucks are designed for them and will not run OK if running too cool such as in short trips. With a 160, as strange as it seems, the thermostat will open at 160 and then remain open and you will overheat eventually. The reason for overheating with an always open thermostat is the coolant doesn't have enough time to dump it's heat as it flows through the rad.

 

Glad I found this thread, my F150 5.0 has been running very hot when I get on the freeway, ever since I blew a hose a few months back.
I replaced the hose and refilled the coolant figuring any air would eventually work itself out of the system through the overflow tank...
but looking into it further, I gather this is not the case.
Does the F150 5.0 V8 not have any air bleeders anywhere along the system?
Many You-tube tutorial videos show these on other makes.
As well as an extremely over-priced funnel system ($50 !) for this precise job of ridding air from cooling systems...
any advice in addition to Kaduh's straightforward brilliance appreciated,
Thanks.

 

Welcome to the jungle kid! I always figured that it was easiest to drain and fill from the top down. That's why I did it that way. I still think it's bass ackwards, but it works, so I'm not going to question it.

I am king of the idiots! I did light up the tires tonight like I was sixteen again!

There is a petcock on the passenger side of the radiator at the bottom so you can drain the cooling system. Make sure you let your truck sit and cool down before you open it!

You're going to learn a lot from these guys, they know what they're doing.