Bongo Fury

Hi All, Had my 2.5d Bongo for over 9 years mainly trouble free, but now have a water leak (or at least I'm having to top up coolant often).

I've looked for the leak, the garage has looked, having had the Bongo for a week and run it up on the ramps hot, left it overnight indoors on cardboard etc. but we can't find where the water is going.

We've tested the coolant, no exhaust gases and its not pressurising. The water goes when its running, and if left overnight/for a few days. Luckily we've got a Hayden Alarm fitted which has saved us so far. White smoke (which we think is unburnt fuel) comes out the exhaist on start up and may last a while, but then after topping up with 500ml of water and restarting later the exhaust may be fine?

Anyone any advice?

Should I keep running it until the leak manifests itself?
Should I bite the bullet and get a refurbished engine or just a head? If yes, where from? Any recommendations? (I can't seem to find a decent 96 2.5d replacement engine?)
Thanks
Levon

It might just be a pinhole leak that only squirts out pressurised steam when its running, sometimes adding UV dye will let you see where the dye ends up spraying onto or wait till its dark and cooler and then with a pencil beam of light look for a trace of steam jetting out somewhere. Another location is around the water pump seals but normally that ends up as a drip coming out of the telltale holes (2 of them) around the belt drive spindle.

Thanks, have ordered some UV dye and will try that and looking in the dark.