Hi guys, I need some advice. I have a 2003 f150 4.6 triton. I had to make a long trip recently and my truck started having problems. I had traveled about 6 miles when the Engine needs service light came on, the temp gage on the dash went to hot and the oil light came on. After I managed to get the truck to a dealership, they found the water pump was bad. Changed water pump and after I left, I drove about 2 miles when it looked like it over heated again. I managed to drive it back to the dealership. Before I took off driving again , I checked to see if I was losing water anywhere and I didn't see any of that. When I started the engine again , temp gage was back down mid way between hot and cold. They changed the thermostat. I drove it again and had the same thing happen. I'm from Georgia and this happened in Tennessee. Seems like when I first drive the truck in the morning, the gage goes to hot, I pull over to check things out, and the gage will drop back down to normal, or at least half way between hot and cold. So my question is where would the temp sensor be located and how difficult is it to change. Thanks for any help.

 

CHT sensor is in the driver side head under the intake manifold, which you have to remove to replace the sensor. Hate to say it, but it could also be a head gasket issue.

 

What we are not hearing about is the loss of coolant in the reserve tank?
Is the hoses indicating there is overheating?
Is the radiator blocked in it's lower area reducing cooling capacity?
Is there exhaust in the coolant by testing?
Is the fan clutch working properly?
Is the cap still holding pressure?
Some one needs to do some work to establish the cause instead of guessing.
Good luck.

 

When this first happened, I had a auto repair shop check it out for since I was on the road. I did lose coolant first time around. Those guys found all hoses good so they said it was one of two things, thermostat or blown head gasket. They changed the thermostat, and it did the same thing. Got the truck to ford, they told me it looked like the water pump. They did the testing for blown headgasket and even showed me how they did the test. They told me the head gasket was not blown. The test they did was the exhaust in the coolant test. Fan clutch looks to be working, pressure holding in reserve tank, no water coming from hoses. I drove the truck back to Ga from Tn with no over heating. Today I let it run for a good 20 minutes with the ac on. It didn't try to overheat, but I thought I would check out the heater. Turned it on and the air never got hot but the engine started to overheat. So I'm still scratching my head. Any suggestions.

 

It sounds like that stealership owes you some money! It sounds like they didn't make any attempt to actually find the problem and only shotgunned it. Did they say WHY they replaced the pump and did you look at it after they took it out? Stop shotgunning and find out what's wrong, otherwise you're probably generate more problems than you'll fix, not to mention the wasted money.

You may want to run a compression test on each cylinder to see if there's a leaking head gasket. A CT will also give you a good idea of the mechanical condition of the engine. Testing for exhaust in the coolant is another good test and is quick and easy. Visibly check the oil for any signs of water in it.

Did the engine actually shows signs of over heating when the gauge showed that it was? If not, suspect a bad temperature sender or gauge.

The "oil light coming on" is a worrisome sign! Over heating should not cause that, unless you INSANELY overheating it! I would worry about that more than overheating since a lack of oil pressure will destroy an engine MUCH quicker.

 

The oil light and coolant lights are together on the same circuit.
Why; because one is as bad as the other for the motor should a real issue develop with either one.
The oil gage and temperature gage are separate.
What are there states when the lights are on?
Question is.. is the cooling system actually over heating?
Heater not offering any heat is an air lock or the core is blocked.
.
Since this is an 03 truck, the dash diagnostics may be helpful in indicating the problem.
You need to enter the diagnostics then know how to interpret the readings on the mileage readout as you step through the test sequence, when the problem is present.
Could be the dash has a fault, the sensor or the harness.
A genuine overheat would put the motor into Limp mode such that the drivability would be affected.
I am offering all the ways to test, so some one has to do it to some logical conclusion.
Good luck.

 

Are you saying that both lights hardwired to come on together? Man, that's BS! Doing that would totally mislead the driver in trying understand what's wrong. IF that's what they did, then Ford should have just installed one light and called it "Engine Fault" or something like that.

 

Try to understand the logic behind the system.
Either overheating or loss of oil pressure is a serious event.
The warning Lamp is likely to be noticed first.
The separate gages are there tell you which is the cause.
You know some drivers will just drive on to possible damage and destruction.
You already have people who ignore CEL indicators as it is.
The system is computer controlled, as such the old ways of looking at things are no longer good enough.
As it is the motors last twice as long as the old ones due to these controls and huge improvements in engine design and oils..
An owner who tries to run around and stretch things is the first to complain about what happens when something goes wrong.
Reference Haynes manual page 12-30 to see the electrical layout.
There you will see the warning lamp for both hi temp and low oil pressure are one lamp.
To the right, on the page, you will see separate oil and temp gages.
Any one who wants to service their vehicle needs to spend some time learning so they are better equipped to deal with issues..
Good luck.

 

OK update on over heating. I have had the exhaust gases tested 3 times. All three tests show there is no blown headgasket. I just got thru running the truck without a radiator cap on the reservoir and coolant, but it looked like water, overflowed. I saw air bubbles in the reservoir, large ones, and once that settled the water seemed to start to flow. I ran the truck for a good 10 minutes and the upper radiator hose was cool to the touch. After the air bubbled out, then the upper hose got hot. Also I turned the heat on high. I got nothing but cold air. I've been advised that what is probably happening is a small pin hole is opening up while the engine is cold ,then closing when it gets hot. I've been told the best thing to do is to change engines. My thoughts are possibly plugged radiator or heater core. How can I test for these problems.

 

You need to drain the system, remove the heater hoses and run pressure water both ways through the core to see if the core is blocked and or needs cleaning.
Yes indeed a small hole can open then close with temperature changes in either direction.
The radiators are put together with rubber like gaskets under compression against the nonmetallic tank ends.
These can get hard and begin to leak intermittently after a lot of age.
With an open coolant jug and a cold start, an over flow when the thermostat opens can be a plugged lower part of the radiator.
Running with a condition like this will show over heating under load but may still cool under very light driving conditions.
It's a matter of cooling capacity deficiency vs engine heat production it can't get rid of.
Do the whole procedure so you know what you got.
Good luck.

 

thermostat