TW is using coolant

did you pressure test it cold or hot?

it was done hot

try it cold, my dad had a similar issue with his car was leaking from the pump but once it heated and expanded it sealed and was fine.

hmmm, that means I have to buy a pressure tester, because to do it hot, i just drove it to my mechanic. Cold, I have to do it at home. For now, I'm just watching it. it's only using about 1L/1000km, which I can top up.

It took a litre of coolant today, so it's still using it. That's in about a month, so about 2000k. It passed a pressure test, no obvious leaks. Had a new radiator, t/stat, cap and top hose. Running well, not overheating, but still using coolant.
Should I be worried?

It's been a long while(mid 1990's) since I drove taxis, but LPG converter problems used to cause headaches with coolant loss.

It seems they still do.

Just on the off chance, maybe you could have the converter investigated, if you have not already done so:

https://forums.justcommodores.com.au...-cured.231311/

Thanks LF6, I was thinking about that. It got a new converter a couple of years ago, but it could still be the problem.
Thing is, coolant use is the only symptom.
Dual fuel is a headache.

Was there any change in the way the car operated/fuel consumption before/after new converter installation?

None whatever, just the old converter had a big coolant leak.

If it pressure tested okay, I’d suggest removing and cleaning both pipes to/from the overflow.

I’ve seen a few times where the return has been full of crud. Coolant heats up, gets pushed to overflow, but then after driving as coolant in the block cools down it doesn’t get sucked back in. Air gets in somewhere instead, and over time the overflow fills up more and more until it starts leaking out.

If pressure test showed no leaks, your problem may lay outside the pressure part of the system.

I’d also pull out the overflow bottle and check it carefully for leaks/cracks.