Donald McPherso

I have a slight oil leak at edge of radiator on my 2005 c180 Kompressor which I only bought a couple of months ago. Didn't see the leak for the underpan till later. I have ordered a new radiator, gearbox filter and seal also new dipstick. I also have problems with the heater. I flushed the system and it did start working again. I flushed again then filled with antifreeze. Heater worked for a few days, then my cooler bottle went down to half and I topped up. Seems to be holding. but still no heat from heater. Tonight I dipped the auto box and the level is high.
I am curious. Could this be where my coolant has gone and could this explain the heater working just after the flush and later not or is there another explanation.