Heater not working; no heater core leaks

[lebee69]

I have a 2001 silverado and the heater won't work at all. The heater core isn't leaking and I'm not low on coolant, so any help would be appreciated.

[brian 1]

are you talking about the fan speeds don't work?

[lebee69]

the fan speeds are working fine, but all I get is cold air blowing out the vents, even with the knob turned all the way to heat.

[brian 1]

you could see if the heater core hoses are hot,if one is hot and the other is cold the heater core could be plugged.

[kenny-1907]

You don't say the year or mileage of your truck but my guess is on the heater core being plugged up. I started having problrms with my heat last year around this time and it was too cold to work on myself so I took it to my mechanic. The thermostat was shot as well as the heater core was starting to plug up. After the repairs all was fine the rest of the winter. Now about 3 weeks ago I was getting poor to almost no heat at all again but the temp gauge was showing normal temps and the coolant level was fine, so back to the garage it goes. Turns out the heater core was plugging up again and my mechanic tells me that with dexcool any build up or settiment that builds up floats where as in the old green antifreeze it does not. So with all this crap floating in the dexcool, it floats to the highest spot in the cooling system which happens to be the heater core and starts gumming it up. It cost me less that $100 Canadian to back flush the heater core, flush out the cooling system and replace the dexcool with the green stuff and I tell you I have never had better heat ever, I actually have to open the window at times to cool it down inside. I also have the sticking actuator for the heat where it does not go onto the cool side so it actually gets unbearable inside at times now untill the actuator finally moves.

[j cAT]

Originally Posted by lebee69

I have a 2001 silverado and the heater won't work at all. The heater core isn't leaking and I'm not low on coolant, so any help would be appreciated.

I have found that when using dexcool must use distilled water and never any sealant pills. i have never had the coolant sludge but many others have had this happen and its because the dexcool gets contaminated with tap water or toped off with non dexcool antifreeze. the first symptoms are heater core plugged, then engine overheating. if coolant is sludged will need total flush, drain block if possible and clean out this goo. I change the dexcool and thermostat every 5 years and so far no sludge or heater problems....use water hose to flush out heater core not too much pressure don't want to blow heater core apart.

[J-Ri]

Using short bursts of air gives a much better heater core flush. You can run water through it all day, then blow air through it, then more water and you get tons of crap out. I did one today on a Jeep, after the water ran clear the first time, it took 10-15 more times with air until it was actually clean. And make sure that the first couple times you flush it backwards, otherwise you'll just pack the sludge in tighter.

[Carwhiz]

temp door actuator is bad, seen it many times at our gm garage where i work, see if both hoses are hot going to heater core. if so, your temp door actuator is not working and is closed on the cold position.