leak down tester
Thread Starter
Race Director
Joined: Sep 2004
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
leak down tester
any body have any good information on using and analyzing the results from a leak down tester? the tester i have has the dual guages with one of the guages calibrated as a % loss that you set to 0. thks bob
Melting Slicks
Joined: Dec 2006
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From: Kingston Ontario
Thread Starter
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
thks that was good reading.....the gauge i have has the gauge closest to the cylinder as a % guage that shows leakage.....the directions say crank up the pressure and set the needle on the % guage to 0.....and then what..... wait???
the interesting part is that on some of the cylinders if you crank up the pressure it actually goes negative.....so what am i missing?
the interesting part is that on some of the cylinders if you crank up the pressure it actually goes negative.....so what am i missing?
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
You need to "0" the gauge as a starting reference point.
Select the cylinder to be tested.
- Ensure you're at TDC on compression stroke.
- Connect the spark plug hole hose to the cylinder. (hose only. Not connected to gauges yet.)
- Hook the air line to the gauges and dial in the regulator until "0" is read on the gauge closest to the plug. (the hose is still not connected yet.)
- Now connect the gauge assembly to the hose going to the cylinder.
- The reading on the gauge at this time will indicate the leakage value.
You will always have a certain amount of leakage, especially on a cold engine. Air leakage past the rings is normal. This test will identify an intake or exhaust valve leak quite well. If your indicated leakage is a large value then you will likely be able to hear the air leakage in the exhaust pipe or intake manifold.
Select the cylinder to be tested.
- Ensure you're at TDC on compression stroke.
- Connect the spark plug hole hose to the cylinder. (hose only. Not connected to gauges yet.)
- Hook the air line to the gauges and dial in the regulator until "0" is read on the gauge closest to the plug. (the hose is still not connected yet.)
- Now connect the gauge assembly to the hose going to the cylinder.
- The reading on the gauge at this time will indicate the leakage value.
You will always have a certain amount of leakage, especially on a cold engine. Air leakage past the rings is normal. This test will identify an intake or exhaust valve leak quite well. If your indicated leakage is a large value then you will likely be able to hear the air leakage in the exhaust pipe or intake manifold.
Thread Starter
Race Director
Joined: Sep 2004
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
ok got it......when i zero it out its at only 15 psi? then i get 100% leak down and a reading of no psi on the first gauge?
this is on a cylinder that i know i have a problem....i hear the air coming out of other intake valves and the carb.
but why is it zeroing out at 15 psi?
this is on a cylinder that i know i have a problem....i hear the air coming out of other intake valves and the carb.
but why is it zeroing out at 15 psi?
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
ok got it......when i zero it out its at only 15 psi? then i get 100% leak down and a reading of no psi on the first gauge?
this is on a cylinder that i know i have a problem....i hear the air coming out of other intake valves and the carb.
but why is it zeroing out at 15 psi?
this is on a cylinder that i know i have a problem....i hear the air coming out of other intake valves and the carb.
but why is it zeroing out at 15 psi?
15 PSI is sufficient for the test.
Thread Starter
Race Director
Joined: Sep 2004
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
ok so all of my quick couplings are compatabile so i did some bench top testing.....so i could understand this thing a little better
at 15 psi on the incoming gauge....0 on the % leakdown gauge...when i hook up a test gauge to the cylinder end it reads the same pressure as the incoming gauge (+/- a few psi) and holds on 0% leak down
at 15 psi on the incoming gauge ----0 on the % leak down....when i hook it up to a "blowgun nozzle" on the cylinder end i can make the %leakdown gauge go from a high of 80% when i press the blow gun nozzle all the way down to 0% when i let off.
i guess the 15 psi zeroing it out at 0% has to do with the size of the orifice in the gauge base
at 15 psi on the incoming gauge....0 on the % leakdown gauge...when i hook up a test gauge to the cylinder end it reads the same pressure as the incoming gauge (+/- a few psi) and holds on 0% leak down
at 15 psi on the incoming gauge ----0 on the % leak down....when i hook it up to a "blowgun nozzle" on the cylinder end i can make the %leakdown gauge go from a high of 80% when i press the blow gun nozzle all the way down to 0% when i let off.
i guess the 15 psi zeroing it out at 0% has to do with the size of the orifice in the gauge base
Thread Starter
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
i understand the guage now thks for walking me through it, the instructions were written incorrectly and had you zeroing out the gauge while it was hooked up to the cylinder.....i can tell that just didnt make any sense after doingit a couple of times. thks again bob
Last edited by bobs77vet; Jan 31, 2010 at 07:46 PM.
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