Heater problem / engine over heating 5.7 hemi 2004, Replaced THERMOSTAT, WATERPUMP,HEATER CORE, FLUSHED ENTIRE COOLING SYSTEM,FRESH DEX-COOL IN SYSTEM, VACUUM FILLED COOLING SYSTEM,HOLDS VACUUM ,RAD IS ONE YEAR OLD

Thermostat stuck open , heater core plugged ! Have you had the cooling system flushed ? Does your coolant look like a muddy color instead of dex-cool orange , you haven't mix green coolant with dex-cool - GM coolant , that would clog the cooling system up .

is there a chance that one of your heater hoses are clogged? or where they connect to the engine are clogged still? sounds like a clogged system. Cracked heater housing? Outside air bypassing the heater coil while driving?

check for a bad blend door or actuator in heater. if bad it will not direct the heat were its called for. good-day !

CHECK TO SEE IF BOTH COOLING FANS RUNNING ARE RUNNING WHEN ENGINE RUNNING START OVERHEATING IF COOLING FANS NOT WORKING CHECK COOLING FANS LARGE FUSES IN THE ENGINE COMPARTMENT OR YOU COULD FAULTY COOLING FANS THERMO SWITCH BOTTOM LEFT SIDE OR RADIATOR.IF COOLING FANS IS WORKING WHILE ENGINE RUNNING.RADIATOR CORES AND HEATER CORE COULD BE CLOGGED.COOLANT SYSTEM NEED FLUSHING. THE THERMOSTAT PARTIALLY CLOSED CAUSE ENGINE OVER HEAT.CHECK WATERPUMP WEEP HOLE IF LEAKING WATER PUMP NEED REPLACING.

Hello! It is extremely important that you only use Dex-Cool in your Cadillac's cooling system...It is Orange in color...If you have used another coolant or the block has not been flushed in some time, flushing is needed...

Drain the cooling system...Do not remove the thermostat...Fill radiator with drinkable water...Turn heat on full...Run engine until thermostat opens...Shut down, let cool then drain...Do this several times until water comes out clean...Replace thermostat...Replace O-rings on thermostat pipe...Coat thermostat bolts with Permatex...Re-fill with Dex-Cool...

Here is Vacuum Diagram...



Guru.Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Normally the engine operates at 195F, if you did not replaced thermostat with another one at 185F. If the temperature has a tendency to rise up, the reason is a partially obstructed cooling system or/and a bad thermostat.
The first part of the cooling system that gives up is the heater core, because the coolant flowing channels are thin. You got a good advice but not the best one. It is the time for a coolant flush in your car. To do do it right then you need time. Plan ahead for a week end. With a cooled engine, start as your friend advised you with the heater core hoses. Disconnect both of them, but the dirt has to go out of your car, so with a garden hose back flush it and let the dirt to get out of your cooling system. After you will get clean discharge, it is the time for coolant bottle, remove it, discharge the used coolant and clean it. The third to come is the radiator. Open the drain cook, or disconnect the lower radiator hose, and disposal used coolant properly. Now open the radiator cap and flush with water the radiator till discharge will be clear. You think that you are done? Not yet. There is half of old dirty coolant trapped in the system.
Install everything, and connect all coolant system hoses, radiator, heater core and coolant bottle. Now you have to run your car with water. Fill out the cooling system with distilled water, start engine, turn on the heater high, and run till upper radiator hose get hot. That means the thermostat opens.
Let the engine to cool down, open the radiator cap, and draining cook or lover radiator hose and drain everything. You can use flush detergent if you wanted at this stage, but flushing with detergent will add 4 more hours, because detergent is colorless and you have to guess how many fill and drain processes do do to get rid of it. I do not do it, but if your cooling system is very dirty you have to do it. After the last drain, fill the cooling system with concentrated antifreeze and 30% distilled water. The reason is because it is more water trapped inside the cooling system. The goal is to reach 50/50 concentration. You need a coolant tester to find this. Start the engine and add coolant til radiator is full. Install the radiator cap and bleed the system. After driving you car for a day or so, let engine to cool down, open the radiator cap check the concentration of coolant with the tester and add antifreeze or distilled water as necessary. It is a good idea to replace the thermostat while flushing the radiator. This procedure has to be done every 2 to 3 years. It is up to you to decide to use RED GM Dex-Cool or GREEN Prestone antifreeze.
In all my cars I have replaced Dex-Cool with Prestone, but I flush the system every 2 years, and I never had a cooling system problem in all my cars.

Start with the simple and replace the thermostat and also replace the coolant. The Dex-cool is only good for 150,00 miles or up to 5 years and any thing longer then that, the coolant crystallizes causing a flow restriction throughout your cooling system.
There is a TSB for thew servicing of coolant that needs to be done before replacing the Dex-cool. The cooling system needs to be flushed out to get the crystal deposit out of the system if there is any.
Gm uses Preston radiator flush to clean out the radiator and heater core of any deposit that will restrict the coolant from flowing throughout the system. Once the system has been flushed out, replace the thermostat and replace the Dex-cool with a 50/50 mix of water and Dex-cool for the best result in cooling. Too much water and the coolant will boil over and too much Dex- cool will jell up causing poor circulation.
Thank you for using fixya and good luck

i'd say that the cooling system is in need of a thorough back flushing with a flushing compound and back flushing kit....hope this is some help....

switch malfunction,blower not working,heating element burnt out.