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Author Topic: Leak down test results, what exactly do they mean? 166 Merlo FELONY MOTORSPORTS Member # 1549 posted                              Wussup Cafords! My engine has 130 and has been boosted for the past 10k. 3rd set of head gaskets currently. still not 100% tuned. most of the air ended up coming out of the valve cover breather and throttle body. Oh yea and I performed the test on a cold engine. how would this affect my results? Cylinders: 4-40% 8-40% 3-20% 7-20% 2-25% 6-25% 1-20% 5-20% -------------------- '89 - Boss Coupe '70 - Drop Cutthang '68 - Cougnut '87 - 0166, Its real Posts: 3953 | From: Thebay | Registered: Jul 2002  |  : JohnB Tech Moderator Member # 969 posted                              Did you rotate the engine over to BTDC for each test?? It doesn't look like it... -------------------- 1965 Shelby Cobra 1993 Cobra 2012 F150 Raptor 2020 GT500 Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002  |  : Mean2001GT ¯ Member # 1750 posted                              with all the head gaskets i'd be concerned if any bubbles were coming out of the radiator during the leak down. but if it's coming out of the breather it means you have blow-by. which is what is supposed to happen, especially when the engine is cold. but 40% is too high. 15%-25% is pretty average. are you chasing a problem? or just testing? another test you may want to consider is a "running compression" test. -------------------- --Silver 2001 GT-- 13.020 @ 110.46 340.2 rwhp 339.8 rwtq Posts: 158 | From: San Ramon, CA | Registered: Aug 2002  |  : 166 Merlo FELONY MOTORSPORTS Member # 1549 posted                              yea i matched up the rotor to the corresponding plug wire to do the test. No bubbles from the radiator I'm kinda chasing a problem, kinda just curious to see. haven't done a running compression test, what the difference between that and a regular compression test? I might have to look into that. -------------------- '89 - Boss Coupe '70 - Drop Cutthang '68 - Cougnut '87 - 0166, Its real Posts: 3953 | From: Thebay | Registered: Jul 2002  |  : hidnn.o.s. ¯ Member # 1219 posted                           From what I've seen, good leakdown numbers are BELOW 10% Goodluck with that -------------------- R.I.P. Willie G. You are missed on this forum Posts: 15950 | Registered: Apr 2002  |  : 88DroptopGT ¯ Member # 2535 posted                              Repeat the test with the engine at operating temperature since this is when you actually drive the car. The readings should be somewhat less then we are getting in reasonable territory. Posts: 3978 | From: 707 | Registered: Mar 2003  |  : hidnn.o.s. ¯ Member # 1219 posted                           Warm leakdown numbers should definitely be UNDER 10% -------------------- R.I.P. Willie G. You are missed on this forum Posts: 15950 | Registered: Apr 2002  |  :

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