Chevrolet Repair: overheating on 03 chevy blazer, chevy blazer, radiator system

Question
my 03 chevy blazer overheated the last time i was in to change my oil they told me i needed a radiator flush is the over heating due to not flushing the radiator

Answer
Oil change shops are not always the best place for a diagnosis.  Changing oil is an act that anyone can be trained to do.  However, diagnosis is better left to the repair shops.  If you cannot tell, oil shops don't impress me.  There is much more money in wrenching.  If they were any good at diagnosis or wrenching, why do they make minumum wage doing a menial mindless job like changing oil?  Remember, those shops are in it to make as much money as they can off people in 20 minutes.  

Now to the problem.  Over heat can be caused by many things.  A few are collapsed hose, bad thermostat, plugged radiator or heater core, over exertion of the motor, low coolant, etc.  

Here is a statistic.  Every 2 years you should flush the radiator system.  That is because antifreeze breaks down due to heavy driving and actually turns into an acid.  This acid etches your cooling system.  Destroys head gaskets, aluminum cooling passages, and radiators and heater cores.  Now what is heavy driving?  Well that is a variable based on mileage driven on average, city or hwy, towing, climate, etc.  

After 4 years I have a hard time believing the reason for over heat is because of lack of flush and fill.  Of course, that is "their" diagnosis, that is something that they sell.  Then when it doesn't work, they will tell you it is becaue it was too late before they did their work. You already damaged the cooling system.  YEA!!

I would start by doing the basics.  Check the coolant level.  Squeeze the big hoses, do they pinch closed by hand easily?  Did this over heat when it was hot out, a/c was on and you were at an idle in traffic?  As you see the temp needle rise, try turning the a/c off and see if the needle stops rising.  Try turning the heat on to give the coolant a place to vent it's heat in the heater core.  See if the needle stop rising.  When the motor is cold, take the radiator cap off and start the truck.  When you step o the gas, does the coolant appear to circulate or move in the radiator?  Is the radiator full of bugs or look damaged at all?  How about the a/c condensor in front of the radiator?  

My off the bat diagnosis/suspicion is thermostat.  That is the first thing any 'mechanic' should suggest.  Oil change shops don't change thermostats.  

Actually a flush and fill is simply dumping the antifreeze from the radiator and refilling.  That is what you get for the money.  They should call it a dump and refill.  There is not actual "flush".  

What you should get is the thermostat pulled, a connection hooked up to the heater core lines and a garden hose connected to this fitting.  The water then flushes the system backward purging the debris from the radiator and heater core out the filler cap.  Run this for 20 minutes until the water comes out clear.  Then drain the radiator again and refill with coolant.  A new thermostat installed and all is then good.  Unless the radiator is plugged inside.  

Sorry about the long answer, and the rant.  I really have a pet peeve about oil change shops.  It is great that they offer people the ability to change their oil thus extending the life to their motors.  But I hear horror stories more often than not about their shoddy work.  Their filter quality and oil quality is in question.  They get sub-standard stuff to keep their price down.  That is how they can do it so cheap.  I don't use them.  I do my own everything.