1989 jaguar thermal vacuum valve

I have a question about the TVV (thermal vacuum valve).

There are two TVV’s on the thermostat housing and as I understand it ported vacuum is always supplied to one side and when the valve warms up it opens and allows the vacuum to be pulled through the other side.

I pulled off the hose that supplies the vacuum to the valve and checked it with my hand held vacuum pump. At idle there is no vacuum at all and when I rev up the engine the vacuum increases slightly and then drops back to zero. That doesn’t seem right.

If you have an '89 and a vac gauge would you be so kind to run this check and see what you get.