Like many TXV systems, the evaporator inlet and outlet are accessible from the engine compartment, once you remove enough of the bits that are in the way. It's still not extremely accessible; you have to fit your hands into a fairly small space to remove the screws holding the TXV onto the evaporator tubes.

In addition to the tight space, the evaporator tubes are quite flexible at the firewall. This made it seem very dicey to hold the flush gun against the tube. It tried to wobble all around with the flushing, and of course caused me to squirt some of the fluid out and all over (myself, the car, etc).

I attached a 6" or so length of an appropriate size of vinyl tubing to the evaporator inlet with a small hose clamp. Not so tight so as to deform the aluminum tube, but tight enough to hold it on. Then I screwed a pipe nipple into the flush gun and clamped the other end of the vinyl tube to this, and hit it with the HECAT magic. I was able to sustain quite a large flow through the system this way, without worrying about placement of the dispensing handle and without losing any solvent before it got into the evaporator.

There was then very little restriction at the connection. The instructions say to use the "large" tip if possible, but it seems that sometimes no tip may be best. It worked like a charm. Is there a chance that no restriction at the tip can cause the wrong sort of action? It seemed to be pulsating quite violently.

I didn't consider gutting the TXV and reinstalling it. That would have made the job somewhat easier, and I did have a new TXV to install. Next time, and hopefully on a different car.

I did use the same setup for the purging and "pop" test.

Thanks for the response.