98 Explorer will not warm up, after a series of events

[WindMill]

I have a 98 Explorer with the 4.0 OHV engine. Have had it since Juli last year and already did some work on it. Yesterday, I noticed a squeeling noise from under the hood. Initially, I thought it was the alternator because I located the sound from that direction. Yesterday evening, while driving home, suddenly the noise became louder , my battery light in the dash came on, then the check cauge light en suddenly the engine temp gauge dropped to "C". Powersteering was still working, so were the headlights, and I decided to just drive it 5 more minutes till I got home. There i inspected the engine and i saw the my belt tensioner pully was completely gone. The expension can for coolant was open (and pretty full) and I saw some coolant was spilled. The belt was resting on the bearings but was still looped over all pullies. Today, I replaced the entire tensioner with a new one and also the belt. Engine runs smooth! However, my temp gauge did not move and also the heat is not really hot.
My guess is I did not see the temp running up during the event untill my eye catched the check gauge light, and in the mean time the thermostat (only 3 months old) did his job and opened up. The belt was still on the pullies but probably did not turn the waterpump enough to keep the coolant cool. I replaced the temp SENDER with a new one after checking the gauge was okay (connector to ground gave full temp reading). No changes. Again, car runs good but does not warm up. Is my guess good and do I need to replace the thermostat or is there something I'm overlooking? Please advice!

 

[koda2000]

you over-heated the engine. that's why the overflow tank filled up and blew the top off. hopefully you didn't crack a head or blow a head gasket. often overheating the engine will ruin the thermostat, you should replacing it. also, you may have to burp out any air that may get trapped in the cooling system or the gauge will not be submerged in coolant and wont register. that's why your gauge dropped to "C" when it overheated and pushed/boiled the coolant out into the overflow and out of the engine.

 

[WindMill]

Thanks Koda, for your reply. I will put in a new stat today and see how it goes. Truck runs great by the way, no signs of water in the oil or a cracked head at this time. No smell either. I hope I got lucky and the heads are okay.

 

[WindMill]

Update: The problem is fixed. Put in a new thermostat and everything is back to normal now. The old one was stuck open so it did wat it was supposed to do! Saved my engine.
Case closed! Keep on Exploring!