Water pump/thermostat vito w447 om651

[Amg 007]

Hi guys what are the symptoms of a faulty water pump/thermostat, I have coolant leak on my Vito w447 2.1 om651 need to top up every few days also heaters don’t seem as hot as before, temp reaches 90
Can see odd spots of dried white residue/crust around pump/thermostat but no obvious leaks & pulley on pump seems fine no excessive play or noises can it still be faulty ?

 

[Jonesy161]

If it’s the same set up as the saloon version, plastic covers under the pump need to be taken off to see if there’s signs of water staining, mine was pretty obvious although it wasn’t using lots of coolant.
I also had a couple of tiny leaks on top and bottom hoses, I solved them by turning the o rings through 180 degs.