[Schurkey]

Huh?

Plug the leakdown tester into your cylinder. You have your leakdown numbers in two seconds, not two minutes. The readings probably stay stable as long as the tool is connected. ALL cylinders leak air, new, old, rebuilt. They ALL leak. What is acceptable for indicated leakage depends on the ACTUAL cylinder leakage, plus the construction of the tester...which I tried to warn you about earlier.

I think you're doing SOMETHING(s) very wrong. Starting with not calibrating your expectations with a known-good engine of similar bore size; or a Master Orifice. After that, I'm thinking you need to read the instructions that came with your testing equipment.

Provide a link to the leakdown tester you bought.

[ericwoo]

Originally Posted by Schurkey

Huh?

Plug the leakdown tester into your cylinder. You have your leakdown numbers in two seconds, not two minutes. The readings probably stay stable as long as the tool is connected.

I think that may have answered my question that there is a problem with the piston rings and it needs a rebuild. Because the reading does not stablize and it isn't an issue with the leak down tester because I can hear it slowly leaking inside the engine and feel it blowing out the dipstick and valve cover caps

it is a cheap tester but is working www.amazon.com/dp/B0D3LD2MD9

Someone else mentioned the rings could be put upside down. Could that scenario create good compression readings but have a leak down test that doesn't stabilze?

[Schurkey]

Originally Posted by ericwoo

the reading does not stablize and it isn't an issue with the leak down tester because I can hear it slowly leaking inside the engine and feel it blowing out the dipstick and valve cover caps

What air compressor are you connecting this tool to?

If this is a small compressor that can't maintain 100 psi while the cylinder leaks, the leakdown tester won't function properly, and the indicated leakage will increase over time.

[NeighborsComplaint]

As others have said, there is no set duration for a test. It is simply the differential between the pressure supplied vs. the pressure maintained by the cylinder and is accomplished the moment the cylinder is pressurized.

Assuming you remove one plug at a time to test, 10% leak-down would be considered acceptable. 20% or higher indicates problems either in ring seal or valve contact.

Following a "dry" leak-down test, you can pour a small quantity of oil down the cylinder and retest "wet". The oil will improve the sealing of the rings. If the leak-down % improves, the rings are suspect.

Conversely, no improvement can indicate leakage past the valves. This is usually accompanied by the sound or air leakage within the intake and/or exhaust tract.

[Schurkey]

Originally Posted by NeighborsComplaint

As others have said, there is no set duration for a test. It is simply the differential between the pressure supplied vs. the pressure maintained by the cylinder and is accomplished the moment the cylinder is pressurized.

Yes.

It takes (much) longer to find WHERE the pressure is going, (Listen at the throttle body, listen at the exhaust pipe, look in the radiator for bubbles, wave your hand around the spark plug holes of the cylinders next to the one being tested) than to look at the gauge(s) to determine the AMOUNT of leakage.

Originally Posted by NeighborsComplaint

Assuming you remove one plug at a time to test, 10% leak-down would be considered acceptable. 20% or higher indicates problems either in ring seal or valve contact.

No.

1. Removing one plug at a time is poor practice, because you might miss leakage from one cylinder to it's neighbor(s). If you put air in one cylinder, and you get air out of the next cylinder's spark plug hole...you have a badly-damaged casting, or a popped head gasket.

2. As I've said before...you cannot pick a percentage number and say that it's "good" or it's "bad". The indicated results on the gauge depend on the ACTUAL LEAKAGE, AND the construction of the leakdown tester being used. There is no industry-standard, law, or regulation of automotive leakdown testers. "10%" indicated leakage on one leakdown tester may be caused by more leakage than an indicated 20% on another leakdown tester. You cannot compare test results from one leakdown tester to another, different leakdown tester.

You MUST "calibrate your expectations" of the leakdown tester in-use by one of two methods: Either test known-good cylinders of similar bore diameter to the engine you have questions about; or use a Master Orifice.

Originally Posted by NeighborsComplaint

Following a "dry" leak-down test, you can pour a small quantity of oil down the cylinder and retest "wet". The oil will improve the sealing of the rings. If the leak-down % improves, the rings are suspect.

Conversely, no improvement can indicate leakage past the valves. This is usually accompanied by the sound or air leakage within the intake and/or exhaust tract.

No.

"Wet" (oiled-cylinder) tests were said to be valid for cranking compression testing. I quit doing those decades ago, because I could not understand how the oil was supposed to climb uphill to seal the rings on engines with angled cylinder bores--V8s, Slant 6 or Slant 4, horizontally-opposed engines, etc.

"Wet" cranking compression testing may have been valid on upright engines--Inline 4 or 6, "Straight 8". But mostly, the compression numbers go up because adding incompressible oil to the cylinder raises the compression ratio slightly.

Adding oil to a cylinder leakdown test is useless in any case...the oil just blows down the ring gaps, or around leaky rings--and the rings ALWAYS leak. It's just a matter of whether they leak excessively.

[ericwoo]

Originally Posted by Schurkey

What air compressor are you connecting this tool to?

If this is a small compressor that can't maintain 100 psi while the cylinder leaks, the leakdown tester won't function properly, and the indicated leakage will increase over time.

Ok, I just made a post and deleted it because I just tried a 3rd time and realized something must have been done wrong.

This 3rd time, I got the compressor up to its max of around 150 psi, then turned up the max exit pressure but only showed around 120 psi.

I calibrated the gauge to 100 psi as instructions show, then tested and cylinder #1 showed around 8-10%.

I assume that should be good for a healthy engine. Regardless, I am happy to figure this out and get a stabilized pressure reading.

Another thing I realized, that even though the exit pressure was maintained 120 psi on the gauge, my old compressor has an pressure release valve that leaks to turn off the compressor when it is at its max pressure. I taped the valve temporarily to ensure it doesnt leak. Not sure if that was causing my leak down test to not get a stabilized reading or if it is because I turned the exit pressure to max.

I am thinking my engine is healthy and may check the transmission next.

[Schurkey]

Originally Posted by ericwoo

I calibrated the gauge to 100 psi as instructions show, then tested and cylinder #1 showed around 8-10%.

I assume that should be good for a healthy engine.

WHERE is the leakage? My standard--not shared by the entire world--is that ANY leakage past the intake or exhaust valve(s) is unacceptable. ANY leakage into the cooling system is unacceptable. ANY leakage into an adjacent cylinder is unacceptable.

The ONLY acceptable leakage is past the rings, and then only within limits.

And without experience with known-good engines of the same bore size, or a Master Orifice, you have no idea if 8--10 percent leakage is acceptable. You can GUESS that it's acceptable. It is PROBABLY acceptable. But you don't know for sure.

And--as said--you still have seven more cylinders to test.

Originally Posted by ericwoo

Regardless, I am happy to figure this out and get a stabilized pressure reading.

Agreed.

Originally Posted by ericwoo

I am thinking my engine is healthy and may check the transmission next.

A failed torque converter stator one-way clutch could produce poor low-speed performance while not affecting higher-speed performance. But that doesn't really match your symptoms.

I suspect you still have "engine" issues, and you've not answered my questions about ignition timing and fuel mixture that I posted quite a while ago.