Cadillac Seville 99 Cooling water loss

Hello dear US community, I now have another problem with my thick. I had for a long time the problem that it consumes about 1 liters of cooling water on 700 km. Was therefore already in three workshops and they meant they did not have a CO2 tester ;-(. Well, because they took it up and generally looked for a leak only found nothing. They then all three started looking for the oil but I told them that they didn’t recognize this with the engine. So I told them the erz Her opinion on this was a shoulder twitch and only meant they had to watch it. Well, thank you for how long I should wait there? So I got on the AB today and first drove nice and meaningfully about 25 km and then kicked the thick on the brush ;-))) happy the sound ;-))) but what should I say almost a quarter tank procedure and the temperature indicator never went over the middle. On the way back I still did it l tried to get the tempomat in at 230 Kmh about 5 min then the Porsche was in front of me and I had to reduce my speed again. But still nothing with the temperature. Then I drove out at the rest area and tried to squeeze together the thick hose which goes long before the engine, went about 1/4 to squeeze together. So dear community how and what should I do now??? Well I never noticed any white smoke when starting. Is that my bonnet quite wobbly at 200 kmh, but it was hard to have checked extra. Ps. the water problem in the trunk I have not yet been able to test since it has not rained until now.