Do all Suburbans & Tahoes have the same bad heater design where hot engine coolant is constantly flowing through both the front and the rear heater cores?
Mine sure does and it makes no sense at all. Even if you have the AC running on a 100 degree day both heater cores still have hot coolant flowing through them! At this point I plan to change this unless someone can tell me why I should not fix this idiotic design. If it is on these GM vehicles it must be the same on most if not all other GM cars.

 

I was under the impression that coolant always flows thru the core, regardless of the vehicle. I've had Fords, Chryslers, and GM's and it's always been that way. To stop the flow, you'd need a valve in the coolant line. Can you expain your specific complaint? I know my heater box is warm all of the time, but I think they adequately bypass it when the AC is on. I have nice cold air, one thing I can't complain about....

 

Haven't check the Tahoe but I know in the past GM vehicles have had vacuum operated valves in the heater lines. They also would run the compressor in the defrost mode if the temp was above about 38*. Did this for two reasons, one to dehumidfy the air heating the W/S and two to keep the compressor seals lubed.

 

I dont understand what the real issue is? Are they leaking? You only need to change it if you are in the South/southwest where you dont need heat.

 

X2 Whats wrong?

 

ALMOST all cars and trucks run coolant through the heater core at all times now. The heater control valve is a thing of the past. Now and days they use what is called a blend door which when on AC the door completely blocks air from passing through the core. Full heat would completely block the evaporator and any temperatures in between opens the door a specific amount to blend evap and core air together to achieve the desired temp.

 

The only car that I have ever owned that had valve operated heater core was my BMW 740iL, and it was more trouble than it was worth.

Most cars use air control flaps to deflect airflow through the core, the AC, or nothing at all. I don't know why you would want to change this, as there really isn't any upside.

Oh, I almost forgot that I used to own an MG Midget that had a garden style valve under the hood that you would open or close to increase or decrease coolant flow. Nobody takes mechanical ideas from MG, for good reason.

 

The problem w/ a hot heater core all of the time is when it resides in the airbox inside the psgr compartment. Even w/ no air flowing thru it, you still got the radiated heated as it heated up the airbox. Don't know it they are still located there or not. Haven't really check recent model years.

I put manual shutoffs on my '73 Corvette cuz you don't need any extra heat in the cockpit on those old ones.

 

I very much agree with 73Shark as I too do not want 200+ degree water flowing through two cores, one front & one rear, radiating heat into the passenger department; I live in south Florida. I understand that the blend door diverts the air flow to either the heater core or evaporator, or a combination, based on temp settings but the extra unwanted heat must be gotten rid of somehow and it just puts more work on the AC and that is inefficient at best. To me this is lazy and poor engineering. Where is the advantage?

 

Maybe just maybe it was engineered that way to help keep the engine cool. I know when you run hot they tell you to turn your heat up high and turn the fan on high. Becides I would rather have it circulating than heating up the one hose really hot.