Leak Down Test?

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Dec 9, 2006 | 07:15 PM

MiaSSmaro98

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From: Miami,Fl

Leak Down Test?

Guys What Exactly Is A Leak Down Test?and Also Im Gonna Do A Compression Test On My Motor And Was Wondering What Numbers Should I Be Looking For?

Dec 9, 2006 | 07:21 PM

Jake@EPP

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From: Hell AFB

A leakdown is a test that shows the amount of seal your combination has. It will show a % of leak. A typical motor should be around 5-10%

Dec 9, 2006 | 07:22 PM

MiaSSmaro98

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How Do I Manage To Do This?and Do U Know Any Info On Compression Testing?

Dec 9, 2006 | 07:22 PM

novass72

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you usually don't want anything below 100psi on a compression test.

Dec 9, 2006 | 07:29 PM

MiaSSmaro98

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Kool,what Tool Do I Use For The Leak Down Test?

Dec 9, 2006 | 08:35 PM

Jake@EPP

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From: Hell AFB

Not to be sarcastic but a leak down tester. You can rent one from Autozone or the similar, you will need a air compressor to use this tool. A simple compression tester you do not.

Dec 9, 2006 | 10:57 PM

MiaSSmaro98

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alright thanks

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Jan 27, 2007 | 11:58 AM

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From: Knoxville, TN

Quote:

Originally Posted by audiopro

I'm fixing to do a compression test myself. Last time I did one was on a carbed engine.. How do you stop the fuel flow on FI when doing a compression test?

pull the fuel pump relay

Jan 27, 2007 | 11:58 AM

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black98ws6ta

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Unplug the injectors.

Jan 27, 2007 | 12:31 PM

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ddnspider

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ive got a question i did a compression test a few weeks back and it was across the board between 100-105 is this good?i know you dont want and large variations but how are those numbers?

Jan 27, 2007 | 12:34 PM

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From: Knoxville, TN

You are just looking for a variation between highest and lowest (over 10% and I would start looking why). Depending on your cam, compression and gauge the actual numbers will vary quite a bit. Mine is around 170psi, with the old engine and z06 cam it was 185 or so on my gauge.

Jan 27, 2007 | 12:35 PM

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ddnspider

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thats what ive been wondering....everyone i talk to is 160 or above...id think something was wrong being only 100-105 but theyre linear across the board.

Jan 27, 2007 | 12:38 PM

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From: Knoxville, TN

Quote:

Originally Posted by ddnspider

thats what ive been wondering....everyone i talk to is 160 or above...id think something was wrong being only 100-105 but theyre linear across the board.

Like i said depends on your gauge also, friend of mine was only 100 or so on his gauge and he borrowed mine and it was 160 on mine. Its also possible you have a bent valve in every cylinder - thats where a leakdown tester comes in. It wont tell you cranking pressure but you can tell right away if something is wrong.

Jan 27, 2007 | 12:41 PM

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ddnspider

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gotcha.how does that work you put a tee spoon of oil in through the spark plug opening and crank it and if it goes way up theres a problem?

Jan 27, 2007 | 12:43 PM

#16

audiopro

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I figured it would be to just pull the fuel pump fuse, which is what I ended up doing...

So far I have done the drivers side 4 cylinders.. Across the board I am right at 200psi on an engine with 130k miles! I am super stoked!!!

I wanted to do a compression test as I am planning to start some light modding. Wanted to make sure I would not need the money for a rebuild, and could thus use the money to mod. So far, I am thinking I am safe to mod!

I'll report back with the passenger side, minus #8 (I aint wasting my time with one cylinder!)

I'll post some pics too!

Thanks for the help guys!

P.S. I am using a Mac Tools CT100 Gauge, it goes to 300psi.

Jan 27, 2007 | 12:51 PM

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From: Knoxville, TN

Quote:

Originally Posted by ddnspider

gotcha.how does that work you put a tee spoon of oil in through the spark plug opening and crank it and if it goes way up theres a problem?

Thats just for checking ring seal, the oil will help seal if the ringsa re really bad. LS1s usualy have enough oil in the cylinders where you dont have to worry about that

If they are that low on all of them and the car is running fine I wouldnt worry too much about it.