Coolant leak at back of engine suburban. I can fill it in the morning and it will have leaked out when arrive to work. It apparently leaks more when I stop. Replace water pump about 6 months ago when leaking toward front right of engine. Now leaking toward back right (passenger side).

Check the water pump and see if coolant is around it.

You must have a coolant leak. If there are no signs of a leak, you may have a gasket on the engine that has gone bad, and the coolant is being pushed out the exhaust system. The coolant expands when hot and cools when the engine cools. During the cooling stage the cooling system creates a suction on the coolant in the reservoir and draws enough coolant back into the system to keep it full. Apparently you are loosing enough coolant somewhere that the reservoir can not fill the system before going dry.

The overheating probably came from the coolant being too low. The coolant in the reservoir won't go back into the radiator if the coolant in the radiator is too low. Until you get it fixed, check and fill up the radiator every time you want to use it. Overheating is very bad for engines and can cause expensive engine repairs.
Where is it leaking, from the engine or the radiator? You didn't say, but wherever it is leaking is the place to start. If at the radiator, and it is not a loose or leaking hose, I would be looking for a new radiator. If it is leaking at the front of the engine and dripping down from there, you could have a bad water pump. This could be an expensive repair at a shop-not the pump itself-they are not too expensive-but the labor cost in replacing a water pump will add up.

The thermostat would not cause it to leak. But when all is said and done, you will want a new thermostat, after the leak is fixed. They are very cheap and it is just good insurance.

Unfortunate you're losing coolant into the cylinders, where it's being burned off and exiting out the exhaust. When you initially added that cold coolant into the hot radiator, and hot engine (sit down) you likely cracked the engine block. Best case you just need to replace the head gasket.

a leak in coolant system will cause air pocket in the coolant system around the engine coolant temperature sensor.coolant sensor is a thermistor in which when hot cool cause it resistance decrease which affect the voltage from sensor to pcm which will cause engine coolant to turn on.if coolant level okay,check coolant fan fuse and relay, if all is good,engine coolant temperature sensor could be bad or have vechicle code scan for pcm problems it control the coolant fan.fill coolant system to correct level make sure engine coolat reservoir is at full cold mark and not empty.fill coolant system check for leaks,refill coolant overflow jug back to full cold mark dont over fill, if coolant overflow stay empty you have leak either its leaking or you have radiator hoses or radiator leaking coolant.when coolant overflow jug run dry it cause air get in coolant system causing overheating problems.

sounds like intake gasket it goes out after about 100,000 miles most of time by fire wall.

CHECK ENGINE OIL FOR SIGNS OF COOLANT,IF ENGINE OIL LOOK OKAY MORE LIKELY WATER PUMP COULD BE LEAKING.CHECK AROUND WATER PUMP SEE IF WET WITH COOLANT.

If you have a pressure reservoir I would replace the cap. When they wear out they will let the coolant out as you drive. Could also be a cracked reservoir. Fill it and cap it. Fill it to the top this time and start the engine. As it warms up, if coolant starts to come out the overflow. replace the cap. And if not you will have to hunt down the leak. If the car is not running bad, then you can rule out internal engine leaks.

The most common sources of leaks that I see on these are where the water pump bolts to the block, the weep hole on the water pump itself, and the seam at the plastic end tank of the radiator [inlet end of radiator]. You'll almost never see any coolant drip on the ground from any of these leaks because of where they are, how slow they leak, and the fact that when the engine is hot the coolant vaporizes about as fast as it can leak. I have a tool that I put on in place of the radiator cap which allows me to pressurize the cooling system to about 17 psi. If its an especially tough one to find I'll leave pressure on the system overnight and come morning the leak is usually quite evident. I'd start by looking at where the water pump bolts to the block as the gaskets there are prone to leaking the most. Good luck, hope you find your leak!

check the condition of the reserve tank and the hose from the reserve tank to the radiator for leaks if no leaks there have the Radiator cap presure tested . also this could be a air lock in the engine if the radiator is new with the engine running and the heater on hot observe the fluid level in the radiator with the cap off if it drops as it warms add more coolant this will purge the air .