I never "had" one - I bought one at Harbor Freight (where the kindly register guy was very careful to tell me I had up to 90 days to return it for a full refund.. which is possibly the reason it no longer appears on the on-line catalog..) and immediately took it to my mechanic and gifted it to him. The HF one had several different-sized tapered rubber sleeves, the smallest sleeve attached to the fitting that connects to the coolant reservoir, and if you need a larger one, it simply slipped over the one fitted on the device. You could stack them up so get almost any size > 1" that you might need.
The actual vacuum pump on the device is a venturi-type vacuum pump:
A good illustration of how one works.. and also shows the need for a constant source of high-pressure air (a pancake air compressor can be used with one - at least I was told someone did - but ideally you want a large piston compressor providing the compressed air..)
In the illustration above - the air is used to create a vacuum that pulls the air out of the cooling system (and partly collapses the hoses). There is then a valve that shuts off the vacuum pump and transfers the connection to the coolant reservoir to a hose that is kept submerged in your new coolant (I premixed mine in a 5-gallon pail, with 50% distilled water. Mine took about 4 gallons of 50/50 mix). The vacuum left in the cooling system creates suction that pulled the coolant up the hose and down into the system.
Easy-peasy. It took 10 minutes. I then drove it home, and after letting it cool overnight I found I needed to add about 300-400cc of coolant to the reservoir. I haven't touched it since then (about 10,000 miles.)
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To answer your question - I think so. I seem to recall the fitting the rubber tapered ring was on (it would be the "vac" above, but after an additional 2-way valve) had flats on it so it could be unscrewed. I have no idea what the threads were on it, or how difficult it would be to actually remove it.
FWIW - when I had a new heating system installed 35 years ago (jeeze time flys..) the plumber added a hose valve on each of the return circuits for the heating loops (4 of them), and to bleed the system you just connect a hose up to them (going somewhere to a drain) and open the hose valve and lift the bail on the fill-regulator so full pressure is available. The water flow through the loop is fast enough that any trapped air is flushed out. Works like a charm (had to get a circulator motor replaced last year..)
EDIT: I looked again on HF's website, and indeed they still have the one I bought as an item for sale.
Cooling System Test and Refill Kit You can see the different size sleeves used to get the correct size.