How long does it take coolant to work it's way into the system?

[carbonspork]

Hello,

I have a diesel auto 85.  Recently, in an effort to fix some overheating, I went to check on my thermostat, and from what I can tell - there isn't one installed.  My guess is the PO just removed it and left it out because it was faulty.  I have one on order, but anyway, on to my point.  During that process, I obviously drained and lost a lot of fluid.  Since then I've noticed the reserve tank empty 2 times.  I don't really drive her that frequently - I live on a tiny island and it maybe sees a tank of gas a month at best.  I did a "test" of sorts on the coolant system, by fitting an air pump onto the resevoir pressure valve, pumping it up to ~20PSI, and unscrewing the radiator bleed valve (to get any air out of the radiator).  I then left it pumped up, and kept an eye on the gauge, and it stayed at pressure, which would make me optimistically think there's not a coolant leak.

That said, I have had to top off the reserve tank twice since I filled it up after the thermostat hunt.  This seems a little strange to me.  I'm also having some transmission slippage in low gear, so I'm kind of concerned maybe the trans cooler is being contaminated with fluid.  Is there some way I can test/verify where the coolant is disappearing to?  No visible leaks in the driveway, and other than a little ugly diesel smoke on startup, everything seems normal (for a 40 year old van with 300KM on it, anyway)

[multisi]

Dont stress just keep topping up the main coolant tank when its cold and when its warm open the rad screw.  You could syphon some water into the rad if you have some thin hose . Open your van heater controls to let it circulate.

[R0B]

A diesel auto that's a rarity.

[Oldiebut goodie]

If I did a coolant change on my diesel I had to drive quite a bit for it to "burp" the last of the air out of the system. Not always but it did behave like that quite often.

[carbonspork]

A diesel auto that's a rarity.

I honestly think it used to be a manual at some point.  The moulding around the gear shift seems like it was cut by hand.  Tenth owner so who knows