It took more than 6 months for me to diagnose that why my Crown was reducing coolant.
All connections & pipes were good. Radiator was Serviced well. Cap was OK though I changed it couple of times to make sure. But yet it was reducing water.
Its fan had a clutch and air throw of fan was really good. Let me call it extra ordinary.
I tried different techniques and consulted with different mechanics too, but no one could diagnose why its reducing water.
Once a very old mechanic told me that your car fan & clutch, both are faulty. I was surprised.
I opened the clutch and it was running out of Silicon oil. I filled the silicon oil, fixed it again and it worked good for
some days only. And then again water reduction started happening.
Finally I got its fan changed. Though only fan cost me 2K+labour, but once I did, it never reduced the water.
Moral of the story, many time we see that Fan is working OK. But infact if its speed is less then normal which is hardly to find out by naked eye, then it will reduce the water.