Last spring I installed a 100% aluminum 34" radiator on my truck. I also reinstalled my LS1 fans (from Camaro). When I first did the install I noticed the engine temperature not getting to "normal". (normal = approximately 195* on the cluster gage and confirmed through my AutoCal.) I decided to change the thermostat because it had 130K+ on it along with the upper and lower radiator hoses. Nothing changed.

I took everything apart again today to confirm everything looked OK inside and then observed some more. The thermostat is opening at the correct temperature and the fans are coming on around 210* and shutting off at 195* (Blackbear Tune). While driving however I am seeing temps in the 150* range (again, confirmed with AutoCal) so I get very little heat inside the cab. I am beginning to wonder because I am using the LS1 fans, which fit the original 28" radiator fine, have too much of a gap along side allowing the cold winter air to cool the radiator too much. Now I know when the thermostat is "closed" no coolant is going through main hoses but it still is being bypassed into the overflow and through the heater core. Would blocking those sides off help? Any help would be appreciated. Just an FYI the temperature has been ranging from -10*F to 20*F or so this winter so far up here in New England.

 

Try a temp gun to confirm

 

I block the front of my radiator with a piece of stainless i got at work.
A piece of cardboard works as well. Put it behind the grille, but dont completely block the radiator. The fans should still be able to suck air through.

 

At -5* what do you expect... haha

 

I know....-5* is damn cold. That is why I want some heat!! I measured the actual core area of the radiator and it is 34"W x 19"H. I may look into making a shroud out of aluminum or just purchasing a set of 34" fans to cover the core itself.

 

Are you sure your stat is working? Mine was stuck open, causing mine to run cold. And like mentioned before, cover the radiotor up some.

 

I would venture something is off. I run factory e fans on my three trucks and in weather much colder than you (-40f) and have never put on cardboard, a winter front or a grill insert in my trucks. I will run at thermostat set temp all day long.... even just idling it never cools off anymore which was an issue I had with the clutch fan and cold temperatures. Now yes my fans are over the entire rad but are pretty open to let air just blow on through. Its more like your thermostat is opening too soon. If its truly closed all the time your upper rad hose should be cold as you have no flow in the cooling system.

 

Update: This morning I decided to replace the thermostat once again. Drained the coolant and replaced the 'stat. Filled her back up and no change. At idle, it will show 200 or so on the gage and confirmed with the AutoCal. While driving I am seeing temperatures anywhere from 140*F to 158* F. Thermostat is definitely closed when these temperatures are being read. Could I have a faulty coolant temp sensor?

 

With your increased cooling system capacity, you will need to add something to block off some of the airflow thru the radiator. This is why the diesel trucks run cold fronts in the winter. They have huge cooling systems for heavy towing, but they suffer during extreme cold weather.

 

B.S. I have the same rad as the OP does... the same setup for the most part being e fans and I am in colder climate that he is and yet have zero temperature issues even in -40F. I own 3 of the trucks too so I have a pretty good handle on what cold weather does. Heck I don't know anyone with a GM truck that has a winterfront, or cardboard, or a grill insert for winter use anymore.

Now maybe since the OP has the Camaro fans it's an issue with the sides opened up.... but that is easily fixed by covering the sides only.

Honestly it makes zero sense as to why the truck would run too cold with no front on it.....hell he isn't even driving in "cold" weather.

Any half ton from 2005 onward is the same deal...... and they warm up just fine here too..... I mean the company I work with only has a few hundred of them and all with no winterfronts.

CTS could be bad.... but the fact you have 200 degrees at idle now shows the thermostat was an issue.