# Simple Leakdown How-to
**URL:** https://forums.speedlife.net/t/simple-leakdown-how-to/12694
**Category:** NYSpeed Automotive
**Created:** [May 30, 2006, 2:19pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694 "2006-05-30T14:19:27Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@Daddie](https://forums.speedlife.net/u/Daddie)
#### Post date: [May 30, 2006, 2:19pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/1 "2006-05-30T14:19:27Z")
A leak down or “cylinder leakage” test is similar to a compression test in that it tells you how well your engine’s cylinders are sealing. But instead of measuring pressure, it measures pressure loss.
A leak down test requires the removal of all the spark plugs. The crankshaft is then turned so that each piston is at top dead center (both valves closed) when each cylinder is tested. Most people start with cylinder number one and follow the engine’s firing order.
A threaded coupling attached to a leakage gauge is screwed into a spark plug hole. Compressed air (80 to 90 psi) is then fed into the cylinder.
An engine in great condition should generally show only 5 to 10% leakage. An engine that’s still in pretty good condition may show up to 20% leakage. But more than 30% leakage indicates trouble.
The neat thing about a leakage test (as opposed to a compression test) is that it’s faster and easier to figure out where the pressure is going. If you hear air coming out of the tailpipe, it indicates a leaky exhaust valve. Air coming out of the throttle body or carburetor would point to a leaky intake valve. Air coming out of the breather vent or PCV valve fitting would tell you the rings and/or cylinders are worn.
A leakage test can also be used in conjunction with a compression test to diagnose other kinds of problems.
A cylinder that has poor compression, but minimal leakage, usually has a valvetrain problem such as a worn cam lobe, broken valve spring, collapsed lifter, bent push rod, etc.
If all the cylinders have low compression, but show minimal leakage, the most likely cause is incorrect valve timing. The timing belt or chain may be off a notch or two.
If compression is good and leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery (bad injector) or ignition problem (fouled spark plug or bad plug wire).
I thought this would be a good “how to”
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### Author:  [@focusinprogress](https://forums.speedlife.net/u/focusinprogress)
#### Post date: [May 30, 2006, 2:37pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/2 "2006-05-30T14:37:11Z")
nice
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### Author:  [@ly555is](https://forums.speedlife.net/u/ly555is)
#### Post date: [May 30, 2006, 4:44pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/3 "2006-05-30T16:44:34Z")
movement for sticky, i just learned something :tup:
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### Author:  [@9ONA3OOZX](https://forums.speedlife.net/u/9ONA3OOZX)
#### Post date: [May 30, 2006, 9:01pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/4 "2006-05-30T21:01:00Z")
:tup:
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### Author:  [@IntegLS94](https://forums.speedlife.net/u/IntegLS94)
#### Post date: [June 10, 2007, 1:32pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/5 "2007-06-10T13:32:49Z")
nice break-down
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### Author:  [@ImportMuscle](https://forums.speedlife.net/u/ImportMuscle)
#### Post date: [June 10, 2007, 3:53pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/6 "2007-06-10T15:53:27Z")
:tup:
Just learned alot there, good read
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### Author:  [@13005TEDGP](https://forums.speedlife.net/u/13005TEDGP)
#### Post date: [June 10, 2007, 8:18pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/7 "2007-06-10T20:18:30Z")
:tup: for putting this up! Its exactly the way I would describe the test and what to listen for. Awsome!
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### Author:  [@Bacon](https://forums.speedlife.net/u/Bacon)
#### Post date: [June 10, 2007, 8:56pm UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/8 "2007-06-10T20:56:42Z")
Well written, yet easy to understand. :tup:
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### Author:  [@reliant\_turbo](https://forums.speedlife.net/u/reliant_turbo)
#### Post date: [August 18, 2007, 8:14am UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/9 "2007-08-18T08:14:16Z")
plus you can take a breaker bar and carefully move the piston up and down and see if any parts of the bore are messed up from rust or scoring or something like that.
Brian
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### Author:  [@system](https://forums.speedlife.net/u/system)
#### Post date: [August 18, 2007, 10:34am UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/10 "2007-08-18T10:34:23Z")
Also make sure if the vehicle is a stick that it is in a high gear 5/6 with the e brake set
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### Author:  [@turbo\_ls1\_ss](https://forums.speedlife.net/u/turbo_ls1_ss)
#### Post date: [August 18, 2007, 10:58am UTC](https://forums.speedlife.net/t/simple-leakdown-how-to/12694/11 "2007-08-18T10:58:13Z")
ughhh. leakdowns
and it helps if the engine is hot so the rings are expanded. ie, less loss through the ring gap.
where did you get your values from howie? im sure theres several different leakdown “satisfactory points”, and im just comparing to the mac setup we use, which said 5% is satisfactory, ~10%+ indicates trouble