Can ANYONE Explain "Leakdown Test" To Me?
TECH Junkie
Joined: Dec 2001
Posts: 3,242
Likes: 0
From: Lakeland, FL
Pretty easy, get a leakdown guage via summit and remove all the sparkplugs from the holes, hook the guage up to your air compressor and inject 100 psi of air into each cylinder at its TDC, you can find tdc by injecting say 20psi and listening for TDC or also its right after the crank gets super hard to turn to super easy. Once at TDC inject 100 psi, look at the 2nd leakdown guage on the tester. if it says 90 then then that cylinder has 10 % leakdown. Also you need to listen to where it is leaking from. If it is going into the oil pan you have blowbuy IE ring/pison issues. If it is out the intake then your intake valve is fuxored. Likewise if you here air escaping out the exhaust its your exhaust valve. If you see bubbles in you coolant than you have a head gasket issue. Its a really cool test to do especially being able to hear wear the problem lies. Also anything above 10 % is real bad, 7-10% is still bad but ok. 4-7 is pretty damn good. Under 4% and your leakdown % is rivaling race cars. I could be wrong slightly on the above % but basically anything up to 10% is ok with 9 and 10 % being iffy.
Thread Starter
Staging Lane
Joined: Feb 2003
Posts: 58
Likes: 0
From: Cold as Hell, NY
Thanks Mike........I appreciate the detailed reponse. Especially the %. Great info. Thanks again......
Originally Posted by Mike K.
Pretty easy, get a leakdown guage via summit and remove all the sparkplugs from the holes, hook the guage up to your air compressor and inject 100 psi of air into each cylinder at its TDC, you can find tdc by injecting say 20psi and listening for TDC or also its right after the crank gets super hard to turn to super easy. Once at TDC inject 100 psi, look at the 2nd leakdown guage on the tester. if it says 90 then then that cylinder has 10 % leakdown. Also you need to listen to where it is leaking from. If it is going into the oil pan you have blowbuy IE ring/pison issues. If it is out the intake then your intake valve is fuxored. Likewise if you here air escaping out the exhaust its your exhaust valve. If you see bubbles in you coolant than you have a head gasket issue. Its a really cool test to do especially being able to hear wear the problem lies. Also anything above 10 % is real bad, 7-10% is still bad but ok. 4-7 is pretty damn good. Under 4% and your leakdown % is rivaling race cars. I could be wrong slightly on the above % but basically anything up to 10% is ok with 9 and 10 % being iffy.
OK Buckmaster!
Finally looking into it! Hands down the best way to determine the condition of an engine. I had hurt of 418 road racing and only discovered it when it was down on power. 522 to 480 RWHP! I did a leakdown test and found 3 cylinders with 14 % leakage through the rings.
I think you have all good parts but maybe your motor is hurt! Get it done!
Finally looking into it! Hands down the best way to determine the condition of an engine. I had hurt of 418 road racing and only discovered it when it was down on power. 522 to 480 RWHP! I did a leakdown test and found 3 cylinders with 14 % leakage through the rings.
I think you have all good parts but maybe your motor is hurt! Get it done!
Thread Starter
Staging Lane
Joined: Feb 2003
Posts: 58
Likes: 0
From: Cold as Hell, NY
They will definitely do it. I just wanted to know more about it for my own knowledge. It should be done tomorrow or so...........
Originally Posted by 9D9LS
OK Buckmaster!
Finally looking into it! Hands down the best way to determine the condition of an engine. I had hurt of 418 road racing and only discovered it when it was down on power. 522 to 480 RWHP! I did a leakdown test and found 3 cylinders with 14 % leakage through the rings.
I think you have all good parts but maybe your motor is hurt! Get it done!
Finally looking into it! Hands down the best way to determine the condition of an engine. I had hurt of 418 road racing and only discovered it when it was down on power. 522 to 480 RWHP! I did a leakdown test and found 3 cylinders with 14 % leakage through the rings.
I think you have all good parts but maybe your motor is hurt! Get it done!
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Launching!
Joined: Mar 2004
Posts: 222
Likes: 0
From: Ontario Canada
So basically this is a very effective and cheap way of finding out if you may have a any of a variety of problems?
Would a valve with even a slight bend show up as too much leakage?
Or any other valvetrain problems that may have occured from accidentally overrevving.
I ask this because while running hard up to 5500 in third I jammed into 2nd instead of 4th.
It was only for a brief moment before I pushed the clutch back in but I saw the tach max out past 7k briefly.
The car still pulls really hard and I dont notice any power loss but I figure this is an inexpensive test.
Would a valve with even a slight bend show up as too much leakage?
Or any other valvetrain problems that may have occured from accidentally overrevving.
I ask this because while running hard up to 5500 in third I jammed into 2nd instead of 4th.
It was only for a brief moment before I pushed the clutch back in but I saw the tach max out past 7k briefly.The car still pulls really hard and I dont notice any power loss but I figure this is an inexpensive test.
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Staging Lane
Joined: Feb 2003
Posts: 58
Likes: 0
From: Cold as Hell, NY
Originally Posted by 9D9LS
OK Buckmaster!
I think you have all good parts but maybe your motor is hurt! Get it done!
I think you have all good parts but maybe your motor is hurt! Get it done!
A leakdown test will test for leaks in both the intake and exhaust valve as well as the rings. With the rocker arms off, both valves should 100% sealed. Some blowby (less then 5%) is acceptable and most likely coming through the rings. If an intake or exhaust valve was leaking, it can be heard through the intake or exhaust system. If both of those are good and the leakage is greater then 10%, the rings are wooped! I would also do a cylinder cranking test as well to add to the testing results!
