Where is the coolant going?
Is it wet inside?
If its loosing coolant there, then it'd be that.
Otherwise, a tk test will rule out any gasketitis.
tk tests if you don't already know, can be done at any good mechanic or radiator shop.
Nope, no leakage into the cabin as far as I could tell.
I don't know where it's leaking to. This kinda worries me as it leads me to believe that it's being burnt off via a leaking gasket. However, the sudden lack of heating leads me to beleive that it must be related to the heater element leaking from somewhere..
Also could be a blockage in the radiator core that's building pressure and pumping the fluid out of the drain pipe and hence not delivering any warms to the heater return...
Could be so many things and I don't have the time or the patience to work on this lump of a thing!
I've checked the oil and there was no milky residue so I don't think the gasket has gone yet.
I've recommended that he take it back to the place that did his water pump and supposedly fixed the initial problem and to aks them to pressure check the cooling system, run an o2 test and investigate the heating issue.
All of that should hopefully varify if there is a bigger problem looming.