Trying to figure out your forum. 2005 Chevy Blazer, bought it new. Eventually like to lift it.
I'm searching for help as I'm not a mechanic, but handy enough to ask for help and eventually get the job done.
My issue today is I live in fl. My heat isn't working. 45 tonight LMAO! I had a radiator flush 2 months ago. the radiator was still full of rusty water.
The Company insured me they flushed it. So, No heat, the passenger side of the floor is dry, I'll start with the thermostat maybe it's stuck.
Somehow look for a link to my heat issue.
I welcome any advice. Thanks.

 

*Moved to '2nd Gen Tech'*

 

Welcome!

45'F? That's tee-shirt weather up here in North Idaho! Well maybe not quite. LOL

As for your cooling issues, search threads on cooling system sludge, cleaning out the heater core by back-flushing and using solvents, and getting rid of air in the heater core (i.e. needing to "burp" it) as a start.

From what I've been able to learn, the original Dexcool coolant if run low or if mixed with the traditional green stuff could create a brown sludge. Modern coolants seem to be formulated to be able to mix but not all can.

Another issue with the heating/AC systems is the vacuum actuated doors that direct the air flow in the ducts under the dash. This failure can be due to leaky vacuum lines in the engine compartment. (I have a thread in my .sig file below on my fix of those lines). Finally the electronically controlled and actuated "blend-door actuator" that controls the temperature of the air in the HVAC system can fail also.

Look for threads on these too to help you diagnose the origin of your problem.

Be sure to report back with any results or if you have more questions.