Inexplicable to me, cold water loss.

Moin! Short and close…about 2 weeks ago I had started my V70 short, drove a bit back, maybe 1 meter, because I had to grow the underbody protection again. So….then done…Enjoyed the Sunday in peace, car stopped….Monday morning, kids threw into the car, got in and wanted to start, he jumped on and speed went down and out….First panic! 4000€ were sunk there last year. ATM, new clutch, new cooler, clean, original cooling flow I was surprised at the first moment… why always, battery charged and still a try…..Just juking…..So, even more panic! Then I thought….schei* on it! If he doesn’t want to do it anymore, I’ll crush him! But not for slaughter! : ) But then let it shudder until it smells funny, rubber. Then he jumped on and since then everything has been fine… He jumps again wie I didn’t want to start it for the one meter, but it was slightly oblique and I didn’t get pushed, or I always came back rolling. What was still after the engine change was a defective thermostat, or giver. Therefore, the thing with the underbody…I just wanted to leave the cooling water off/absorbe reasonably! But I also changed both components. In addition, there I am still researching, he loses some cooling water somewhere, etc. What was that? he. I can’t see where….how can I do it best? He doesn’t know….just in the morning, always short…But that doesn’t fit with the water loss, because the crowd goes very slowly fluted until it’s just under “min”!