SB&D also rebrands them as Proto along with Mac I think. All my Proto gauges seem identical to OTC.
Some Mac tools are OTC rebrands. Makes sense that Proto does the same thing.
OTC USED TO make great tools. OTC
makes almost nothing any more, they import junk from Asia, especially China. I have the OTC vacuum gauge, and the OTC oil/transmission pressure tester set. All Asian. I feel cheated.
Leak down testers are over rated imo. If you have a problem you can just hook an air hose directly to the hole with a line setup for it. Never really figured the percentage was useful.
You need the percentage because it's impossible to estimate the amount of air blowing past the rings any other way. The noise of air escaping from the valve cover or oil fill tube is misleading.
Leaking intake or exhaust valves are easy: any leakage is too much. Same with bubbles in the radiator. But virtually all engines allow air past the rings. Unless you can quantify it, you cannot know if it's acceptable leakage or non-acceptable leakage.
I used to do what you suggest--back in the 1980s. It will do a fine job of checking ring seal and compression loss to the cooling system. Doesn't work worth a **** for finding bad rings or piston-land faults.
I would buy anything OTC sells.
Only if it's offered on a STEEP discount; because you're buying import **** that may or may not be better than Harbor Fright.
Bosch has all but destroyed OTC; although I won't promise that the decline didn't start prior to Bosch ownership. There was a time that the OTC Stinger line was the cheap import stuff, but not any more.
For the record, if you're looking for a leakdown tester you probably should investigate the ones having a "master orifice" so that you can calibrate your readings to a known leakage source.
Remember that a leakdown tester's
indicated results are influenced at least as much by the orifice size in the tester as the actual cylinder leakage. Worse, there is NO "industry standard" for the orifice size in automotive applications. Unless you have SOME method of comparing to a known leakage source, you have no idea if your gauge set reads high or low. Until the "Master orifice" concept came along, the only way was to test multitudes of "known-good" engines of various cylinder bore sizes to get an understanding of how your particular gauge set reacts.
The Master Orifices included with this Aviation gauge allows for too much leakage for automotive applications, but at least it's a baseline. Checking the leakage with the master orifice, then allowing only 1/4 or 1/2 or 2/3 of that amount might be reasonable.
https://www.amazon.com/dp/B005VR9H24/?tag=atomicindus08-20
The "Three Sisters" of engine diagnostics:
Cranking compression test (a running-engine compression test is less useful, but uses the same tool)
Cylinder leakdown test
Cylinder power-balance test (especially if you can short-out every other cylinder along with shorting individual cylinders.)
Stand-alone cylinder power-balance testers are getting exceedingly rare. I had a hand-held KAL that worked fine, and there are still some Snap-On units floating around. I forget the model number. Some scan tools will perform power balance testing, but of course you have to have a new enough vehicle.
Worst case, you use a 12-volt test light. Ground the wire, then the pointy probe is wiped with silicone grease and slid between the spark plug wire and the plug (or distributor) boot to ground-out the spark, killing that cylinder. If the RPM and/or vacuum does
not drop, that cylinder is already weak or dead.
