Picked up a 2000 tahoe a month ago and it seems the heat is not working. It worked the night I bought it, not the next night. Since then it either doesn't work at all (usually) blows warm at best (sometimes) or works fine (rarely). The hottest it will blow out the dash is as hot as the rear heat will blow, but I thought the rear heat had a separate heater core....? It seems the issue is universal between the front and back because when it doesn't work at all on the dash, the rear heat is the same, no heat.

I found the cabin filter was extremely plugged so I replaced that. Also, is I grab the heater core lines under the hood one is very hot and the other is just hot... So it seems the core may be working fine.

 

Sounds like gelled Dex-Cool antifreeze in your lines. Do a full system flush with cooling system flush chemicals and then refill with anything not Dex-Cool. Make sure you purge the whole system with water prior to putting different antifreeze back in.

 

do a full flush. probably never been done befor. Dex Cool is fine as long as you dont mix other crap with it.

 

I agree with suburbazine, flush it good and get fid of that dex cool crap . All that stuff does is clog heater cores, I run the good ol green and distiller water in all my vehicles and never have clogging issues .

3 winters in a row I had to flush my sisters heater core out , and also my Tahoe when I first bought it , switched to green and problem solved .

 

if the coolant is green..... i had a new pump put it i could get the dam fan clutch off so this guy put it in my stuff is green i dont want to mix the new purple stuff with it right?

purple is dex right?

 

Orange/Red/Pink is Dex-Cool. You'll never see the pink version unless you open a Land Rover with a Jaguar engine, though.

Purple sounds like VW/Audi G12 coolant. I don't know about it's mixability but I wouldn't recommend it.

Royal Purple has stuff called Purple Ice, it's a water wetter, is that what you're talking about?

 

Irony is it was too cold to fix this and flush the coolant lines so I just drove my tbss all winter. Found a weak actuator motor for the front temp door and now I get hot air in the back but cold or really warm air up front. Guess I had more than one thing broken.

Does the front and rear heat use different heater cores? I imagine I still flush via the two main lines coming off the water pump?

Supposed to warm up soon so I can flush the thing with water and let the excess water run down the driveway. Ill bucket the coolant of course.

 

Front and rear are separate cores. The rear unit very rarely has problems with sludge- it's much lower flow than the front core and sees less deposits. Yes, you can flush the lines using the two hoses coming off the pump by the thermostat. Be careful though, the plastic Y on one side is VERY fragile. Break it and you're buying a $150 hose assembly.