What is a leak down test?
Thread Starter
TECH Enthusiast
iTrader: (6)
Joined: Mar 2005
Posts: 700
Likes: 7
From: Kansas City, MO
What is a leak down test? People recommend it for cars that burn oil and smoke. What is it, how is it done, cost, etc...??? I searched but its not working, so Im just looking to see whats involved w/ this.
well, to burn oil, oil must get into the combustion chamber. negating the possiblity of it leaking from the top end (bad valve seal for example), it will have to come from the bottom....meaning it would have to get past the piston ring. now, i dont know for sure, but im guessing its to test the seal of the rings.
that being said, i have no idea how its done
that being said, i have no idea how its done
A leak down test is essentially a more complex compression test.
It involves screwing a special tester into a spark plug hole, setting that cylinder at TDC, locking the motor, then connecting an air compressor to the leak down tester.
What the tester measures is the rate at which air "leaks" down through the engine. It's kinda cool because sometimes you can hear exactly where the compressed air is escaping and immediately identify your problem.
It can test for a lot of things including cracks in the block/head/water jacket, messed up rings, messed up head gaskets, etc.
It involves screwing a special tester into a spark plug hole, setting that cylinder at TDC, locking the motor, then connecting an air compressor to the leak down tester.
What the tester measures is the rate at which air "leaks" down through the engine. It's kinda cool because sometimes you can hear exactly where the compressed air is escaping and immediately identify your problem.
It can test for a lot of things including cracks in the block/head/water jacket, messed up rings, messed up head gaskets, etc.
Originally Posted by Da Swami
What the tester measures is the rate at which air "leaks" down through the engine. It's kinda cool because sometimes you can hear exactly where the compressed air is escaping and immediately identify your problem.
It can test for a lot of things including cracks in the block/head/water jacket, messed up rings, messed up head gaskets, etc.
It can test for a lot of things including cracks in the block/head/water jacket, messed up rings, messed up head gaskets, etc.
If you hear the excessive air from the crank case, your Rings are bad, cracked cyl/head, etc. If you hear if from the intake, bad valves. If it is coming from the valve cover and from the area of the springs.. it most likely is the valves and/or seals.
I had about 5% or less from my 99' LS1 take out.. was in good health and prove to be a good runner once I got it running. But from the test, I had good reason to beleive that the engine was going to be good.
Thread Starter
TECH Enthusiast
iTrader: (6)
Joined: Mar 2005
Posts: 700
Likes: 7
From: Kansas City, MO
Thanks for the fast responses guys. Makes sense now. Is this something I need to let a "professional" do? Like at a shop or something. Or can I get a tool and do it on my own?
Originally Posted by Da Swami
A leak down test is essentially a more complex compression test.
It involves screwing a special tester into a spark plug hole, setting that cylinder at TDC, locking the motor, then connecting an air compressor to the leak down tester.
What the tester measures is the rate at which air "leaks" down through the engine. It's kinda cool because sometimes you can hear exactly where the compressed air is escaping and immediately identify your problem.
It can test for a lot of things including cracks in the block/head/water jacket, messed up rings, messed up head gaskets, etc.
It involves screwing a special tester into a spark plug hole, setting that cylinder at TDC, locking the motor, then connecting an air compressor to the leak down tester.
What the tester measures is the rate at which air "leaks" down through the engine. It's kinda cool because sometimes you can hear exactly where the compressed air is escaping and immediately identify your problem.
It can test for a lot of things including cracks in the block/head/water jacket, messed up rings, messed up head gaskets, etc.
You should be able to buy the tool or rent it.. you just need to find a good way of locking the crank from rotating at TDC/BDC.
I was lucky to be able to do the test with my engine on a stand and not in the car..made it easy to pull the plugs, put he air adapter on and also lock up the crank/flywheel at TDC.
and you will need a Air Compressor that can do 90+ psi (or 100+).
I was lucky to be able to do the test with my engine on a stand and not in the car..made it easy to pull the plugs, put he air adapter on and also lock up the crank/flywheel at TDC.
and you will need a Air Compressor that can do 90+ psi (or 100+).
Trending Topics
Thread Starter
TECH Enthusiast
iTrader: (6)
Joined: Mar 2005
Posts: 700
Likes: 7
From: Kansas City, MO
Sounds like it might be something I need to let someone w/ experience do...
Thanks again for the help. I might just change valve seals first and see if that solves the smoke issue.
Thanks again for the help. I might just change valve seals first and see if that solves the smoke issue.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever
Verdad Gallardo
Originally Posted by bczee
You should be able to buy the tool or rent it.. you just need to find a good way of locking the crank from rotating at TDC/BDC.
and you will need a Air Compressor that can do 90+ psi (or 100+).
and you will need a Air Compressor that can do 90+ psi (or 100+).
Yes, Putting it in gear and blocking the wheels will do the trick, providing your Clutch doesn't slip. There is usually a bit of movement between the gears, rear, u-joints, etc.. but if you get it right, the crank will stay put long enough to get your readings.
