As Ali pointed out, you have coolant in a number of distinct places.
A suction device might draw coolant from the radiator, but there would be no way for it to also pull from the engine and heater core.
You might try evacuating the radiator which is the messiest part of the project using your suction device(or some variation of it). The engine drain plug in many cases is easily accessible and no where near as messy to deal with. You open the plug and then quickly attach a length of hose that points downward into a pan that's been placed underneath the vehicle.
In the early fifties, there's was a commercial gadget that garage owners could use to remove coolant, but it only removed coolant from the radiator. While I do not condone it, even today you find alot of service facilities that only drain the radiator and not the overflow tank and engine block.
1991 300-SEL - Model 126
M103 - SOHC
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