My truck is getting hot. 1994 Ford F-150XLT, 4.9L. Started overheating last July; replaced the thermostat. That didn't help. Then the radiator had to be replaced because I had never changed the coolant (learn from your mistakes). It started getting hot again recently, especially when the air conditioning is on, so I flushed the radiator and changed the coolant. Still overheating. The radiator is full with 1/2 coolant, 1/2 water. No leaks. The Ford dealership said if the fan turned freely, the fan clutch was bad. The fan turned with a healthy amount of resistance, so I believe I can rule that out. They also said the water pump was probably ok, based on what I told them. I guess I am leaning toward a thermostat. Do the brands differ a lot? If there is a holy grail of thermostats out there, let me know, that's probably the one I'll buy. If I am missing something else, I would greatly appreciate any help. Thanks.

 

do you think maybe a radiator hose or the water jacket is clogged with debris, or maybe your temperature sender is inacurate? thats about all i can figure would be it, after the things you said you checked.

 

also, is the motor running lean? this will also cause overheating.

 

Do you check the time? it can also can make your engine get hotter...

 

How would I check the time? I believe that the lines are clear of debris. What exactly would "running lean" be? What is a temperature sender? Bear with me, I am no mechanic. Thanks.

 

the temperature sender, is on the thermostat housing,by the upper radiator hose, it sends the temperature of the water, to that little gauge on the instument panel, that shows the water temperature, as for the motor running lean that means there is less fuel than air in the air/fuel ratio, vise-versa, running rich means there is too much fuel in the air/fuel ratio.
as the other guy said timming can effect this, if you timming is over advanced, this will cause the engine to run lean,it will also spark- knock,you can check your timming if it is off a bit, retard it to the proper degree,i belive for your inline six the timming should be at 10 degrees btdc, there is many sensors on the engine that could cause it to run lean as well, like the MAP sensor,the throttle positon sensor, and so on.
if you cant do any thing else take the truck to a mechanic.

 

When my thermostat went out, I tried THREE different ones. All bad. I finally got pissed and went to FORD and bought one. Works great, has a bigger opening for coolant to flow through also, and has a vavle to prevent airlock in the system.
(To check a thermostat, put it in a pot of boiling water. If it doesn;t open soon, its no good.)

 

Will ,
The fan clutches are often an overlooked cause of engines running hot . You cant go by the resistance it takes to turn it. The fan engages when the bimetal spring mounted in the center of the clutch senses the heat from the radiator . It begins to coil up as the temp increases , Usually about 200 F . These springs over time become less resistant to heat and thus you get little or no engagement . I have a 300 as well and when mine engages it sounds like a DC3 taking off . I replaced mine with a Hayden last summer when mine died , it was about $40 . If you find yours has failed , you will need a special tool to remove the fan and clutch assembly from the water pump . It is right hand thread , because the fan is a reverse rotation . The tool will run you about $60
Paul

 

well i dont need no special tool to remove my fan clutch, i have a nice big pair of channel locks i put on that clutch then i grip the pulley with my hand and that sucker breaks loose, by the way dont forget to loosen it the way the fan turns.

 

by the way gas milage is no concern to me, as far as the fan clutch is concerned, my fan clutch is starting to get ill, it also isnt that old, im thinking of get a spacer and letting the fan run full time, i may also get a flex fan as well.

 

Since the coolant was neglected to the point of needing a new radiator, I'm wondering if perhaps the heater core may be plugged up causing a restriction. Try disconnecting both heater hoses at the water pump connection and thermostat housing connection. Lay the hose which was connected to the water pump over the fender (out of the engine compartment) and hold a garden hose against the end of the other hose. This will back-flush the heater core of any scale and debris and you will determine if the core is plugged. Another suggestion is to remove the water pump and inspect the condition of the impeller inside the pump housing. Anti-freeze contains corrosion inhibitors and if the original coolant was bad it may have damaged the impeller. If the pump is still good then re-install it and your only out the cost of a new gasket and a couple of hours of your time.
As for the factory fan clutch, if it's working properly it is more than adequate for your truck. I drive and tow with my '91 4.9L in the desert southwest and have never had an over-heating problem.
Good Luck, Vern

 

Just like Motorcraftsman said, Use a socket and ratchet on the tensioner pully to apply more belt tension to hold the water pump pully in place and use a large pair of channel locks to unscrew the fan clutch nut.

 

I cant believe nobody mentioned cleaning the radiator and condensor out.
Alot of debris gets packed in between the radiator and condensor. You should be able to loosen up the top mounts on your truck and look down beteen the radiator and condensor and check for yourself. Take a garden hose and a sprayer and clean it out. Start with the back side of the radiator and spray through the radiator move throughout the radiator cleaning out the fins when done spray from the condensor side keep repeating until it flushes klean.
This is a great habbit to start periodically.
If your turck has over a 100,000 miles on it it more than likely needs a fan cluth.
This is a good place to start - fush then change thermostat and finaly fan clutch.
Also check the fins on your condensor and make sure there straight and not bent over blocking air form coming thrugh.
Good luck.

 

The radiator is less than a year old, and the work was done by a shop that the big Ford dealer here takes all of their radiator work to. Also the fan clutch seems ok to me; the fan turns with a good amount of resistance and doesn't really spin freely, which is what the Ford dealer said it should do.

 

Will ,
I understand the fan spins with some resistance , but is the fan engaging when it needs to such as in stop and go driving , running the A/c ? Does the engine run hot at highway speeds ? If the rest of the cooling system is ok , engine isnt running too lean , timing is ok , radiator and A/C condensor are relatively free of bugs and debris ,the shroud is in place ...the only thing left is the fan clutch . Trust me ...you cannot go by the amount of resistance it takes to turn the fan by hand and tell whether or not it is engaging when it should and at the speed it needs to be turning .
Paul