Honest, all I did was drain my cooling system and fill it with water and some flush. When I was done the Engine Temp light would not go off even though the guage showed normal. I let the truck sit for a couple of hours and started it up and the light went out. However, after about 3 miles of driving the light came on again. The guage still showed that everything was fine. Anybody have an idea of what the problem is and how to fix it?? Would it have something to do with running only water in the system?

The truck is a '97 F350 Powerstroke 7.3

Jeff

 

Are you sure you've got the system full of water? If so, there are a few things you can do, depending on whether or not you want to find out why the light is on. If you do want to know, hook up a code scanner. If not, pull the #9 fuse in the fuse box under the hood on the driver's fender, and leave it out for a few hours to drain any residual power from the pcm. When you replace the fuse, you will have cleared any/all codes and you're starting fresh at that point.
As to the cause, I'm guessing that you might have had an air pocket in the cooling system, and the sensor might have picked that up. If it were me, I'd double check to be sure the cooling system is full, then I'd run the truck long enough for the thermostat to open with the heater on high to circulate coolant as well as possible prior to pulling the fuse.
Good luck.

 

Possibly there is air trapped under the thermostat. This happened to a forklift at work.

 

Thanks for the replies!

I have let the truck warm up and cool down twice. Both times I've had the heater full open and I have made sure that the upper hose got hot telling me that the thermostat opened as it should. Could there still be an air pocket? If it happens again this morning I will give pulling the fuse a try.

Do you know if this light is simply a backup for the temp gauge or does it possibly monitor something different? In other words, is it okay to drive it like this to flush the system as long as the gauge reads normal?

Jeff

 

I think you have trapped air and that one part of the engine is getting hot enough to complain. I'd suggest that you starting with a cold engine:
1). remove the radiator cap
2). turn the heater to high (temp & fan)
3). start the engine and let it warm up while you are looking at the temp & coolant level - this should clear any air lock that you may have in the vehicle. It is important that the thermostat open and that the heater is delivering heat.

That is about all I remember from my youth in a radiator shop.

Good luck

 

Well, here's what happened this morning. I drove my son 2 miles to school and the light did not come on. After walking him into the school I came out and started the truck and the light was on. I drove home but at one point the warning light started to flicker and went out for a moment or two. Then it came on again and stayed on the remainder of the trip home.

Here's what I have done this morning.

I found out that the sender that makes this light go on is below the alternator. I unscrewed the sender almost all the way and opened the radiator cap to be sure there was liquid and not air behind it.

I also unplugged fuse #9 under the hood to reset the codes and the truck is now sitting for a couple of hours at which time I will try it again.

At this point if the above doesn't work I think my next step is to replace the sender. Maybe while the air was trying to purge it got excessively hot and ruined it. Other than that I'm out of ideas.

Jeff

 

I got it fixed!!!!

First I filled the system with distilled water to clean out the flush letting each gallon drain out of the overflow before I added the next........same problem.

I then took the sensor out to check if it was actually changing resistance by first sticking it in ice and then boiling water. It was but since I don't have a manual I was unsure if it had the right resistance values or not. Two funny things were that I was never able to get it to show no connection and when I put it in boiling water bubbles came out from around the insulator.

Then I added the coolant so slow that there was never any in the tank....basically dribbled it in.....same problem. Let it cool once more and took it out for a ride. This time the Engine Temp light came on before I hit the entrance to the sub while the other guage still read cold. Now I was convinced it's the sensor.

Called every auto parts in the area and either they didn't carry it or it would take 3 weeks to get one. Finally called Ford and yes they had one.......For $55.00!!!!! Had no choice so today I picked one up and Viola....problem solved!!! Funny thing was that when I showed up at Ford they gave me the dealer discount and the total was under $25.00. Maybe I looked as though I needed some pity. He said that $55.00 was their matrix price whatever that is.

Anyways, vacation on!!!!

Thanks for the help!!!!

Jeff

P.S. Is it okay to use superglue on cuts deep enough to require stitches......I sure hope so!