I went to start my 2001 blazer w/ the 4.3 vortec auto trns and realized that the heat wasn't getting warm. And in 20 degree temps it was very noticable. I drove into town about 20 miles drove around for a little while and came back home. Still no HEAT! So I called my buddy a master tech and went to his garage on the way there still no heat. En route I stepped on it all the way to the floor to pass a drunk driver and went from 15 to around 70 is when I let off. And out of nowhere the heat starts to get hot. I drove it all the way there with the heat working. I turned the heat on and off hot to cool and it was still working. He looked it over and couldn't find anything a miss. He checked the lines going to the heater core and they were both hot and the coolent levels were normal. I know that I should take this as a sign and leave it be, but I am wondering if anyone has any ideas of what it could have been. Or has anyone ever experienced this before. And should I still take it in to the dealership to get it looked at. BTW its still under warranty.

 

I'm really skeptical on the coolant level. Next time it happens, check the temp of the hoses.

Taking it to the dealership to get warranty work done will probably result in a "tech can't duplicate problem" unless you take it to them with the problem happening and don't pass any drunks on the way there.

 

Thanks for your input but I am positive on the levels, but hey it worked all the way today from NC to NY with plenty of warm air to go around, so I guess its no harm no foul.

 

i had the same thing happen in my 95 mx6 2.0l , so to cure it, i changed the thermostat and took the radiator out and brought into the house and put in the bathtub and flushed it out and all this brown and black crap poured out and i put in some rad flush stuff i had from NTB where i worked at the time and let it sit over night with it in it and then flushed again the next morning and VOILA! worked like a charm and NEVER have i seen such clean antifreeze in my life lol...

btw it got to -9degrees here when it happened so i assume it just froze the water part/s of my mixture ?? i dunno but the flushing worked great so thats my new rememdy for anything like that from now on lol

 

Well, I'm glad that it worked during your trip! Sounds like it might have just been a spuratic thing. Maybe the t-stat stuck open that once and now its back to working. If that is the case, then it'll probably happen again.

Anyway, where in NY are ya headed?

 

Sounds like a bad thermostat or air in the cooling system.

 

I am up here in Baldwinsville, right outside of Syracuse. Very upset to not see any snow falling while I'm here. But at least we are driving up to the mtns on wed so I will get plenty of snow there.

 

Try flushing the heater core, mine would get plugged, then unplug itself many times with the heat loss ending up on the coldest days here. I flushed the heater core and it has worked since.

PS. This has happened twice, once before a coolant flush, then right after the flush... good flush to clog my heater - I was not happyon a-40 C day

 

Well its gone again. I checked the return hoses and one was warm but the other wasn't. The fluid levels are all normal.

 

Different temp heater hoses would lead me to a restricted heater core. As suggested before, I would flush the core very well in both directions.