what is a leakdown test
- Thread starter romgolferman
- Start date
A leakdown test is not the same as a compression test as I'm sure you already know. Must use a special gauge specifically designed for a leakdown test. I understand the gauge is not exactly cheap and can be gotten from both aviation and automotive sources.
One face of the gauge measures the pressure of the compressed air that you are forcing into the cylinder, and the other face measures the percentage of this pressure that is being lost. There is a knob on the gauge that lets you control the pressure going in so you get even results.
1. Take out the spark plugs.
2. Bring the cylinder TDC (top dead center) so that all the valves are closed.
3. Screw the gauge adapter into the spark plug well and connect the gauge. The guage has a fitting to connect the extender hose to the spark plug well, and another to connect the air hose.
4. Apply the compressed air and modulate the knob to get a steady reading from both faces on the gauge. Use the same pressure on all cylinders.
5. LISTEN to where you can hear the compressed air.
At the crank case: Remove the oil filler cap. If you can clearly hear a whooshing/howling by listening at the oil filler cap, you're losing compression through the rings.
At the tailpipe: It is your exhaust valves if you can hear it (or even feel puffs on your hand) at the tail pipe.
At the intake manifold: It is your intake valves if you can clearly hear a whooshing/howling by listening at the throttle body/intake manifold. If the results are inconclusive, it is probably your head gasket. If you suspect a blown head gasket, which has symptoms such as reduced power, white or blue smoke out the tailpipe, oil in the coolant or coolant in the oil.
6. Repeat for each cylinder.
You might just want to call around and find a shop that can do this for you unless you want to spend the money on the equipment to do it yourself.
U.M.
One face of the gauge measures the pressure of the compressed air that you are forcing into the cylinder, and the other face measures the percentage of this pressure that is being lost. There is a knob on the gauge that lets you control the pressure going in so you get even results.
1. Take out the spark plugs.
2. Bring the cylinder TDC (top dead center) so that all the valves are closed.
3. Screw the gauge adapter into the spark plug well and connect the gauge. The guage has a fitting to connect the extender hose to the spark plug well, and another to connect the air hose.
4. Apply the compressed air and modulate the knob to get a steady reading from both faces on the gauge. Use the same pressure on all cylinders.
5. LISTEN to where you can hear the compressed air.
At the crank case: Remove the oil filler cap. If you can clearly hear a whooshing/howling by listening at the oil filler cap, you're losing compression through the rings.
At the tailpipe: It is your exhaust valves if you can hear it (or even feel puffs on your hand) at the tail pipe.
At the intake manifold: It is your intake valves if you can clearly hear a whooshing/howling by listening at the throttle body/intake manifold. If the results are inconclusive, it is probably your head gasket. If you suspect a blown head gasket, which has symptoms such as reduced power, white or blue smoke out the tailpipe, oil in the coolant or coolant in the oil.
6. Repeat for each cylinder.
You might just want to call around and find a shop that can do this for you unless you want to spend the money on the equipment to do it yourself.
U.M.
Good explanation of leak down testing.
The only thing that I would add is that you can do this with most any gauge, by simply calculating the loss percentage manually. There are a number of low cost leak down testers. Try googling for automotive test equipment and you will find many sources of such equipment.
The only thing that I would add is that you can do this with most any gauge, by simply calculating the loss percentage manually. There are a number of low cost leak down testers. Try googling for automotive test equipment and you will find many sources of such equipment.
Dusstbuster
I love meat more than anything! I just have a spec
if anything it means somethings getting in there that shouldn't be and it's not lubricating your engine the way it should be...usually milky/frothy is a sign of coolant leaking. While many times that is a sign of a bad head gasket, I had this problem when I did my manifold swap and the intake manifold gasket wasn't sealing properly and allowing fluid to flow from the coolant port to the air intake ports on my heads....I got lucky because changing a head gasket would be a huge PITA from what I concluded after doing the cams.
BlackenedSVT
Active Member
you talking blowby past the piston rings? you think the piston rings are bad?
Try running a "wet" test on it. Do a standard compression test with a gauge. check the reading of the compression test, and record the compression of the cylinder. Then put a few drops of oil down the sparkplug hole and then run the compression test again... if the compression INCREASES, you have blowby and the piston rings are bad.
What this test does is the oil that you put in the cylinder seals around the rings. So if compression is increased after you add the oil, its because the oil is making a better seal that the rings can no longer provide.
Try running a "wet" test on it. Do a standard compression test with a gauge. check the reading of the compression test, and record the compression of the cylinder. Then put a few drops of oil down the sparkplug hole and then run the compression test again... if the compression INCREASES, you have blowby and the piston rings are bad.
What this test does is the oil that you put in the cylinder seals around the rings. So if compression is increased after you add the oil, its because the oil is making a better seal that the rings can no longer provide.
BlackenedSVT
Active Member
03ghoststang
Well-Known Member
i agree you might have blown head gasketSimilar threads
