I bought a twin gage sealey leakdown tester last year. On the reading gage the needle always goes all the way down. This may be that the engines I've used it on have been bad, or the gage doesn't work properly. I rely on listening for leakage, to locate the course of low compression, or pressurising the water.
I did use it before to rebuild my own 2003 2.0 front wheel duratorque 85 hp. the gage was going all the way down then, I had the engine on the floor, and after I lapped the valves in, I bolted the head on with the old head bolts, and leak down tested it, and found some of the valves were leaking, I re-did until it sounded good, I was getting slight leakage from the rings, but the compression readings were 380, 360, 380 and 360 psi,on completion. When finished I did use new head bolts. My van has been fine for a nearly a year.
On the van I'm working on now there is no leakage from the valves on cylinder 2 but a bit from rings so A top end rebuild wouldn't do.