I had previously posted this in the Explorer section but thought would be best it post it here instead with a small update.

Ok wanted to get post this before i go to bed and get some sleep afore i get started on this. Here is the scenario: I'm about 30 miles from home when my temp gauge pegs out. I pull over and stop to check things out. Top radiator hose from the engine to radiator is very hot and very hard no sponginess to it all. Radiator cap is cool to the touch . Lower radiator hose is cool . Yes I know you arent supposed to open the radiator cap after the engines been running but I did anyway. And promptly got cold fluid splashed on my hand. Decided to turn the heater on full blast and see how much closer i could get to home. Well. driving the speed limit or even a bit slower i made it the rest of the way home with the temp gauge staying at around 3/4ths of the way. Avg speed home was around 55mph mostly freeway. Now once i got it home I checked it out again. the Radiator cap was warm to the touch with the rest of the radiator being quite hot yet the return side and return hose was nice and cool. No loss of fluid that I've found. The reservoir is still full. I'm thinking I've got a blockage in the radiator and not that my Water Pump has died out on me. This is on a '99 Explorer 4.0L SOHC with about 93000 miles. Whats everyones opinions?thoughts?

Well after letting it sit for a while I went back out this morning to check it out and see what i can determine. Checked the fluid level inside the radiator and it was full. Started up the car to see if the problem might have miraculously fixed itself (yeah right). But of course it didnt. But once it got to a point of actually heating up both the upper and lower radiator hoses were now hard to the touch with the temp gauge now pegging at 3/4ths of the way or slightly higher but never getting to the overheat stage. Wondering if the temp gauge may have fried itself from the initial Overheating so that it no longer judges temperatures correctly? Or if the sensor had jsut gone haywire. After about 10 minutes of idling it never reaches the H just sits pointing straight up at @ 3/4ths . I can put the heater on full blast to alleviate some of the engine heat and that will bring it down to about midway on the scale but,bottom hose is still quite stiff but only mildly warm to the touch . Upper hose is stiff and hot as one would expect. I wouldn't expect the radiator to cool it off so well while sitting at idle that the hose would only be mildly warm to the touch. Someone in another forum had suggested that possibly the pump had cavitated causing the initial overheating. not sure how that would ahppen as the coolant system hasnt been opened in at least a month with no change in fluid levels. Probably gonna change out the sensor just for the sake of ensuring that it didn't burn up and now be giving me fasle readings.

 

Sounds like a bad T-stat

 

ding ding ding .we have a winner. What was confusing me till I got the thermostat out and thought about it was the fact that the upper hose was hot and hard to the touch. I had forgotten about the small hole in the thermostat that will allow some water to be forced out.

 

Yeah with the pump trying to pull coolant thru that little tiny hole, you would think the hoses would be trying to collapse & not be hard as a rock. Go figure. Glad to hear the T-stat did the trick though.