Heating Problems?

Hi everyone. I have a 1999 Tahoe with 101k. I have noticed sometimes that while im driving my temp gauge just goes up from about 180 to 220 for a few then comes back down to 180. Usually when this happens i also notice that my heat has gone kinda cold. Even if the temp gauge doesnt go up after awhile of driving (it varies times) it will get colder. I was thinking my heater core is going out. I have heard that commonly there will be a puddle on the passanger floor board and have not seen that so far. Does this sound like a heater core problem to anyone else or does anyone have any suggestions? Thanks for any help!

Do you know if someone put regular anti-freeze and mixed it with the Dexcool?

If the 2 are mixed, then from what I was told by my dealer, that the mixture will turn into a gel that clogs the heater core.

I flushed mine and replaced it with the regular (green) antifreeze. I've read too many problems with Dexcool.

Hardwarz

I do all the work on my vehicles unless i am unable to and i have never done anything with coolant to this tahoe. I believe i am kinda low though and going to pick some up tonight and see if that helps. I have heard that if you are low then your heater will not stay warm long either. Anyone know if that is true.

if you drive and your low on dexcool, it will start to turn into a greasy mess. it starts collecting under the radiator cap. i was told its because your get air in the system.

seems to be a common problem... the first 20 or so tahoe's i looked at had the problem.

i've also read numerous places that switching to green antifreeze is just as bad, as it doesn't have the lubricant mixed in it that dexcool does. (mainly for the waterpump) this kept me from buying a couple tahoes.