I had the same problem.I think my waterpump's inside fan went so there was poor circulation. The temp would jump and the oil gauge read hot.ended up with a blown head gasget. I suggest getting the head gasget cheched with a dye test.

 

Having same issue...I noticed a few weeks ago that my Exp was heating up a little faster than usual and then the the temp gauge would fall to ice cold and heat up again. THe heat would not work until the cycle had completed. I also had what sounded like a creek running under my hood when I accelerated.

Took it in last week and flushed the system and changed the t-stat. Ton of junk in the system. That was Friday.

Friday night drove to Vermont, no water sounds and the heat worked but as it got colder it worked less and less. Sunday the problem came back. Stared it and it heat up faster then usual and then cooled down but the temp gauge shot up and the light came on. Shut it down and it went to normal in a few seconds. THis morning it did it three times.

The problems I notice the most it is the lack of heating power. If I run AC MAX the system can heat pretty well. If it is really cold, the normal Panel mode with outside air will cool down the heater in a matter of minutes. THe rear heat cranks out heat however. It also only has this issue from a cold start.

Has anyone found the culprit to this proble?

 

I see the last post was dated in December, '07. Has anyone found the answer, or did everyone load it up with stop leak and peddle it??
My son now has this problem with his '97.
He's replaced T'stat, rad. cap, heater core (ouch). Going to replace water pump this weekend. A friend of his also mentioned clogged Cat converter. What's the warranty on those things?
Any help....
Thanks guys.

 

Post what exactly your sons truck is doing. Just this truck, there's allot of old posts in this thread. How long has he owned the truck? How many radiators has it been thru - how many miles ? Have you or anyone pulled the sensor's to clean the brass bulb ? How the upper intake look right in front where it rests on the head ? The two water jackets in that area tend to leak on the 97-98 models - both sides. Heres a pic of why that is -



The heads pit around the water jackets. See that plug on top of the pic - It's white, you can see some of it. Anyway, that's your Cylinder Head Temp sensor (CHT) - guess where coolant goes when the heads are pitted and the gasket starts leaking. Well if coolant comes in contact with that sensor - That could be a big problem and might even be whats going on. Just a thought.

 

I have a 97 4.6 and was having the same issue. I know it's not what you want to hear, but I would bet the farm you have a blown head gasket. My truck is in the shop as we speak, I'm having both sides done with coolant system flush/clean and new Motorcraft plugs, 1600 bucks, 2 year warranty. This is a very labor intensive job. The dealer wanted 2200.

 

YEP >>> YEP>>>> HEADGASKET, 20 hrs at the dealer...................... remove cab......... I was qouted $3500. TTFN