Cylinder Leak Down Test, How to Do |
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Cylinder Leak Down Test, How to Do |
iiibdsiil |
Jan 13 2004, 12:14 PM
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#1
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
How can you do a cylinder leak down test? What, if any, special tools are needed.
- Brett Smith |
Dave Blackburn |
Jan 13 2004, 12:30 PM
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#2
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Member Group: Members Posts: 116 Joined: 9-April 03 From: Issaquah, Wa Member No.: 551 |
Hey Brett,
You need a special leakdown tester. It measures the amount of air leaking from the cylinder when it is at TDC. You should be able to buy one for around $50 from most auto stores. Here is an article about building your own. http://www.xs11.com/tips/misc/misc3.shtml Good luck! Dave |
smrz914 |
Jan 13 2004, 09:17 PM
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#3
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Soon to be brightening the life of the person behind you. Group: Members Posts: 456 Joined: 21-April 03 From: Pleasant Hill, CA or Chico, CA Member No.: 596 |
Not sure what you know of them but you remove the spark plug and screw in a hose into the hole. Then you take compressed air and connect it to the guages. The piston should be at TDC and you should have the wheels blocked so the car doesn't run you over. (almost seen this happen). If you do get excessive leakage you can diagnose where the leak is. In no particular order. With the cylinder presurized listen inside the intake for escaping air. If you hear some, your intake valve is not sealing. Then listen for air at the exhaust pipe, and if you hear air your exhaust valve is not sealing. Then take the oil cap off and listen for air their, if you hear some it's your rings. There will always be some air leaking, nothing is perfect. I belive 4-8% is still in the good range but this will clearly be marked on the tester. Good luck
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redshift |
Jan 13 2004, 09:36 PM
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#4
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Bless the Hell out of you! Group: Members Posts: 10,926 Joined: 29-June 03 Member No.: 869 |
You do this while your engine is at operating temperature.
M |
iiibdsiil |
Jan 14 2004, 12:25 AM
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#5
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
Thank you very much guys.
Ran a compression check on my motor today, because theoretically the rings are bad, but they all came up to 181 psi, so the leak down is a definite now. I was hoping that the problem was going to be quite evident, and so far, it's not. - Brett Smith |
redshift |
Jan 14 2004, 01:47 AM
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#6
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Bless the Hell out of you! Group: Members Posts: 10,926 Joined: 29-June 03 Member No.: 869 |
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ArtechnikA |
Jan 14 2004, 08:06 AM
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#7
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(iiibdsiil @ Jan 13 2004, 10:25 PM) Ran a compression check on my motor today, because theoretically the rings are bad, but they all came up to 181 psi... the oil ring doesn't hold much compression but it does keep oil out of the combustion chamber. you can have high compression (and good leakdown numbers) -and- bad oil rings ... |
iiibdsiil |
Jan 14 2004, 09:00 PM
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#8
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
Hmmm... That's interesting. I am trying to diagnose the problem before I spend all the money to tear the whole thing apart. Labor is not an issue, but the money for potentially wasted parts is.
Thank you though. I am hoping the problem is going to be real evident, and so far, it hasn't been. Fucker. - Brett Smith |
ArtechnikA |
Jan 14 2004, 09:23 PM
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#9
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(iiibdsiil @ Jan 14 2004, 07:00 PM) Hmmm... That's interesting. I am trying to diagnose the problem before I spend all the money to tear the whole thing apart. well - let us help you. what is the engine, and what is the problem ? |
iiibdsiil |
Jan 15 2004, 08:17 AM
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#10
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Needs Door Locks Group: Members Posts: 605 Joined: 19-November 03 From: Tampa / Boca Raton, FL Member No.: 1,362 |
It's an 88 911 3.2 that's in my 914. I can't tell if it has blow by at idle, but when there is pressure on the motor, i.e. in gear driving, and I punch it hard, like passing someone narrowly, and it shoots oil out the overflow tube on the oil tank.
We are thinking that maybe, just maybe, the drain tube, since it is stock for the 2 liter 6, doesn't flow enough air. So we are going to look at doubling the size and seeing if that solves the problem, also. The motor is not overfull of oil, I have ran it down off the dipstick and it still does it. Then of course, I put it back to midway on the dipstick. Any idea's on what to check? - Brett Smith |
McMark |
Jan 15 2004, 10:06 AM
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#11
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
Just as an extra tidbit, you don't have to have guages to do a leakdown test. The guages just tell you how much air is leaking. You can just use a high pressure hose that has a quick disconnect on one end and a threaded connector on the other. Thread it into the spark plug hole while the piston is at TDC compression and plug in the air and listen as described above to see where things are leaking. This is really effective when you have a cylinder with low compression and you want to find out if the head is the problem or if the rings are the problem.
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ArtechnikA |
Jan 15 2004, 10:28 AM
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#12
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(markd@mac.com @ Jan 15 2004, 08:06 AM) You can just use a high pressure hose that has a quick disconnect on one end and a threaded connector on the other. K-D has such a tool, with adaptors for a couple popular sizes of spark plug. found it on the pegboard of the FLAPS for about $6. it's also used to apply air pressure to a combustion chamber so you can replace valve springs without the valve falling into the open cylinder and i think the name on the blister pack is aimed at this use "Valve-Holder Tool" or somesuch. NPT fitting so you can just screw on the kind of shop air adaptor you use and rock... |
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