I have a 2002 Expedition 4.6L with 115,500 miles. After driving on the freeway for 1.5 hrs the temperature gauge began to rise to about 3/4. Stopped on the side of the road for about 30 min and then drove on. Temperature gauge went down then went back up to being pegged out. The temperature gauge went up in a jerky motion then went down then back up. Got it home replaced the Cylinder Head Temperature Sensor and the T-stat. Started it up ran for 10 min, While watching the coolant temperature on my scanner it slowly rose to about 200 deg. T-stat opened up then about 3-4 min later the temperature suddenly rose to 251 deg then jumped to 273. Check Engine Light came on and it ran horrible. Checked the actual temperature on the engine and it is running about 160-170 deg via a temperature gun. Disconnected the Cylinder Head Sensor, turned the car on and the temperature gauge is going all over. Fan clutch has tension when hot. THe check engine light code was P1299. Please help!!! I am stuck.

 

From your description it sounds like a plugged up radiator.

 

Ok..I will give it a try. I replaced the water pump today. I took the original out and the bearing seemed kind of loose compared to the new one. Just waiting for the new radiator to arrive. Will let you know. Thanks.

 

Not that my 2001 4.6 had any temp issues, but trying to understand what coolers were underneath, I kept looking up under the radiator. The point is there was some leaf debris that had accumulated on the lower part of the radiator fins between the radiator itself and the AC unit. I only have 70,000 miles. Took the plastic cover off up top and used a vacum and lots of water to clean everything up. I didn't have a temp issue, just saying you never know, you are doing lots of work anyway, so take a look.

 

Me too...plus I had a dead bat stuck down there as well!

On a serious note, you are making the right decision on the water pump as well. If you are going to do the work, might as well do it all. If you haven't done hoses, now is the time to do them as well if they feel real soft. Mine were not that bad, but I figured do it now and save a headache later.

 

Replaced the radiator today and.......it still didn't solve the problem. Now I have replaced the water pump, Cylinder Head Temperature Sensor, Radiator Cap, T-stat and flushed out the whole system to no avail.......Arrrgh.....I am out of options. Took it to a respectable mechanic and he said it sounded like a short somewhere or a ground that might be bad. Won't find out until late Monday. I will post the results with hope that no one else has to go the route I am.

 

Well after a few weeks of trouble shooting the mechanic figured it out. It was an electrical problem. The mechanic told me my computer is bad. The computer is reading the volts from the Cylinder Head Temperature Sensor incorrectly. Causing the computer to believe the vehicle is overheating. This will be the 3rd computer in the vehicle. This one has a year warranty so we will see. Hope this helps someone trouble shoot this.

 

That's a weird and unusual problem/solution.