So I noticed the car has been rather cold this winter, and the coolant temp never got up to temp.

I checked the thermostat and it had failed open. I replaced it with a 195, bled the system thoroughly and I am still not getting much heat, it seems to top out around 190 based on the gauge.

I am wondering if perhaps the canned tune from ZZP is turning the radiator fan on too soon and keeping the temps low.

What else should I be looking at?

 

I wouldn't worry about it, that might just be me though.

 

Well call me crazy, but I actually like having a warm car in the winter.

 

What kind of weather are you having? In colder weather the engine will radiate more heat into the atmosphere and run cooler. When it was in the 20s/30s around here with snow my heater didn't blow as hot as it normally did. Once the temps made it back into the 40s the heater started blowing hot again. Other possibilities could be a partialy clogged heater core or a vent blend door that isn't functioning properly. I don't know what temp the tune on your PCM turns the fans on, but I guess that could be another possibility. 190° is about right for an engine with a factory recommended temp thermostat though. Is your heater set to outside air? If so change it to recirculated air and see if that helps.

 

I'm seeing little difference in temperature of air being blown into the cabin with outdoor temps from -10 to +30 and coolant temp in the 190 range.

ZZP states the fan on temp is set to 180 in the tune. Does anyone know what the factory setting is for the L36 Monte Carlo?

 

I think that stock T-Stat is 185.

Since you said your ZZP tune turns the fans at 180, but you have a 195 T-Stat, to my understanding, that is the first problem. Since the fans kick on lowering your operating temp before the T-Stat opens, the T-Stat never opens like it should, thus not circulating the coolant to give you any heat.

You could try looking if you can get a 175 or lower T-stat. I would not go to 160 though (that seems WAY too cold to try and get any heat in the car).

 

Tune is a problem, your fan speeds are on before normal operating temp. 195 is the stock thermostat.

When was the last time the coolant was flushed also?

 

Did u happen to have overheating problems before this?.......Could have a clogged heatercore? Even though mine is a 99...it still smokes me out inside...(super good heat) and i have to turn it down...my stock thermostat also is 195.....maybe the temp controls arent opening all the way?....Chevy heaters are well known to have Plenty of heat dsipite outdoor temps....I would recommend a good "hot" flush of the system...or possible heatercore....even if the fans come on at 180 to start cooling it down....180 degrees is still plenty hot to produce heat!.....Maybe just Maybe...you have to much antifreeze in the system...and not enough water mixed in?.....I would check your ratios...take an antifreeze checker to see where your at.....That should tell you if you have way to much antifreeze in your system.....Hope this helps....would be curious to find out if that is the problem your haveing...

 

How did I not notice the tune/thermostat discrepancy, that makes perfect sense. I'll see what I can get for a new stat, seems all the local guys only carry 180 on the low end.

Coolant is overdue to be done, but I haven't had time . I might just as well flush that out now.

It has never overheated.

 

The 180 thermostat is the lowest I would go. Even with a 180, the car just isn't going to get that hot in the winter.

Flushing the coolant alone might get you some of that heat back honestly.