Quick Tech: How to Use a Leakdown Tester
Using a leakdown tester is one of the best ways to assess the health of your engine.
Easy to use, a leakdown tester measures how much cylinder pressure is escaping from your cylinders, showing how efficiently your piston rings and valves are sealing the combustion chamber, along with your head gasket. With street engines, ten to twenty percent leakdown is typically acceptable. For race engines, the acceptable leakdown is one to ten percent.
If you have one or more cylinders that have out of spec leakage, this points to a problem with sealing in the engine and usually requires disassembly to properly diagnose and repair. If you’ve just built a motor, doing a baseline leakdown test before it has run is ideal, so you can track your engine’s performance and wear over time.
Here’s how to do a leakdown test of your engine:
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I have been using a lead down tester all my life in the aircraft industry. You failed to say that with air going into the cylinder the engine will try to turn over. You need to hold the crankshaft in place to take a reading also you can rock the crank to bring the pressure reading up a little, just make sure you return it to tdc for the reading. Listening at the intake, exhaust and case or block breather will tell you where the problem is.
Old school technology coming around that the auto industry!