In the leak down test you move the up to tdc because of cylinder choke then work the prop back and forth to seat the rings. Test the engine at operating temperature for the best results.
Page 79 3rd Edition 2017 Tool News
Diesel leak down test. In a cylinder leak down test the engine is placed on tdc of the cylinder in question. This cylinder leak down tester gauges leak down tests more accurately than standard compression tests. The tester then measures the volume of air needed to maintain a predetermined pressure in the cylinder. One gauge on the tester measures the pressure of the air entering the cylinder and the other measures the percentage of the air escaping or leaking from the cylinder. Then using a similar type of connector as the compression test we fill the cylinder with pressure. An engine leakdown test is a compression test in reverse.
Compressed air 80 to 90 psi is then fed into the cylinder. Leak down tests on diesels in aircraft the leak down test is used because you dont want to stand next to a spinning prop doing a compression test. Instead of measuring the engines ability to create pressure compressed air is introduced into the cylinder through the spark plug hole. A cylinder leak down test requires the removal of all the spark plugs. Leak down is the percentage of compression that is lost by the engine and every engine has some. A threaded coupling is screwed into a spark plug hole.
Like a compression test a leak down test is accomplished by replacing a spark plug with the tester hose. Disable fuel injection by pulling the fuel. Unplug the coil wire from the distributor to prevent the engine from firing while testing. The performance tool w89729 leak down test kit can quickly diagnose internal engine problems such as bad rings valves and leaking head gaskets. Pressurized air is supplied to each cylinder and in moments displays a rate of leakage measure from 0 to 100. 10 millimeters and 14 millimeters thread adapters dual 2 12 inch chrome bezel gauges and rugged protective outer shell pressure regulated manifold with quick couplers and all comes with an easy to open blow molded hard case for storage.
Unlike a compression test a leak down tester has two gauges and requires a compressed air source. The crankshaft is then turned so that each piston is at top dead centre.
Gallery of Diesel Leak Down Test
