I recently swapped in a ls motor into my hatch back to replace another ls that I had that spun a rod bearing and it seems like right after I did the swap my heater stopped working. I dont know if it has to do with the heater core or its something else little but heres the stuff I have tried:

-replaced the heater core coolant valve
-completely bled coolant so absolutely no air bubbles are in the system
-new thermostat (engine gets up to temp no problem)
-checked coolant hoses, one goes to pass side of the head under dizzy the other goes to water pump fitting deal.
-I manually switched the coolant valve to flow coolant through it.
-car does not loose coolant
-hose going to and hose going from heater core are both hot to the touch.


if any one has any ideas, I don't know why it would stop working like this. I did run radiator stop leak in it about 400 miles ago and now when I turn the heater on it just blows cold air. really not looking forward to replacing the whole unit :/

any insight will be greatly appreciated. thanks in advance.

 

Having sort of the same issue, except every now and then I get some heat... temp gage stays normal and my lower rad hose stays cold... hopefully we find something soon cause its cold as hell in in NE VA!!

 

discovered the problem was due to the cable going to my heater box, it was disconected from when I pulled the dash along time ago (wasn't a big deal, If I wanted the heater on I would just use the coolant valve under the hood)

but when I put my wideband in the car the wiring pulled it to the shut position, for any one who doesn't know what Im talking about and has this problem it is just to the left of where the passenger puts his or her left foot and has various rods and plastic connectors to change from ac to heat and what not, just push it towards the firewall and heat will go through the vents ahh this makes me happy been driving my stupid car like this for two weeks in mid 30 degree weather.

 

hows your coolant level?

 

A tad low but not really bad.

 

have you tried a new thermostat? your problem sounds kinda funny.

 

Yep, this is the second one. I just had an epiphany today though as it overheated on the way home from work.... top hose was hot as hell and blowing coolant into the overflow, bottom hose was ice cold and so was the entire lower half of the radiator... I haven't even thought about the rad being clogged up! I'm betting thats my problem!

 

very well could be.