The thermostat is located behind the engine (crazy design). You will get a better access at the bottom of the engine with vehicled jacked up to replace the thermostat. (Note the orientation of the original thermostat because you don't want to put the new thermostat in the wrong direction).
Now, since they replaced the water pump before, have they replaced the thermostat as well?
To drain the cooling system, just remove the overflow reservoir cap. Locate the radiator drain plug at the bottom of the radiator (driver side, facing the engine). I use a small 1/4" ratchet to turn the drain plug counter clockwise to open it.
Here's my procedure when I flush my cooling system.
You might have to rig up and install a manual overide of the radiator fan so you can turn the fan manually while driving the in the city stop and go.
I would recommend its time to do hands on with your vehicle. If you are willing to learn about your vehicle, the less likely you will be ripped off. Get a male relative or a friend to help you.
Do you have the orange color coolant or the green color coolant? Get the right color for your new coolant replacement $6 each (3 or 4 of them). Get a coolant flush solution $4. Fluid drip pan.
Drain the coolant from the radiator drain plug, open the overflow reservoir cap to drain it faster.
Close the drain plug and put water in the overflow reservoir until full (I would suggest to use a water gallon so you can measure how many gallons it takes to fill the radiator) and put back the overflow reservoir cap. Start the vehicle for 10-15 minutes (you might want to select the heater and fan blower to max) and turn off the engine. Drain the cooling fluid and open the overflow reservoir cap.
Close the drain plug and pour the Cooling Flush solution and then fill the overflow reservoir with water and close the overflow reservoir cap. Start the vehicle for 10-15 minutes (you might want to select the heater and fan blower to max) and turn off the engine. Drain the cooling fluid and open the overflow reservoir cap.
Close the drain plug and fill the overflow reservoir with water and close the overflow reservoir cap. Start the vehicle for 10-15 minutes (you might want to select the heater and fan blower to max) and turn off the engine. Drain the cooling fluid and open the overflow reservoir cap.
Close the drain plug. Now, remember how many gallons it took to fill the radiator when filling up. Check your manual on how many total gallons of coolant it takes to fill the whole cooling system. Draining does not drain the whole cooling fluid and that is why it's important to know how many gallons it take to fill the radiator.
Example, if it takes 4.5 gallons to fill the radiator after it was drained and if the book states that it takes 6 gallons to fill the whole cooling systems with fluid, we know that it has 1.5 gallons of water still left in the cooling system even after draining it.
We want to have 70% coolant and 30% water.
30% of 6 gallons is 1.8 gallons of water.
70% of 6 gallons is 4.2 gallons of coolant.
If 1.5 gallons of water is left in the cooling systems, then we just need 0.3 gallons of water added and then 4.2 gallons of coolant.
If you want to use 50% coolant and 50% water then
we just need:
50% of 6 gallons is 3 gallons of water.
50% of 6 gallons is 3 gallons of coolant.
Since we have 1.5 gallon of water left in the cooling system, then we just need 1.5 gallon of additional water. We just need to add 3 gallons of coolant.
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