Using New Leak Down Testing Tool
 

I am admittedly a bit dense sometimes but am trying to use my new leak down testing tool from HarborFreight. I hook everything up and I can hear the air through the oil filler but the gauge reads 0% leakage? I can hear it leaking so I know it is not zero - is the tool broken? (it is HF after all) What is the typical pressure when zeroing out the % leak down gauge? Mine reads 12 psi - seems low but the pressure may be irrelevant when determining leak down?

Thanks!

do you have your cylinder being tested at TDC on the compression stroke? You add 100 # and what is read from the connection is the leak percentage. Hold the crank because if it's just off TDC, it will rotate under the pressure. This can sometimes be a little unanticipated surprise.

Vance,
I bought a HF leakdown tester last year. I had problems because the second (right hand), gauge was 30# max pressure.
It read in a range rather than useable numbers.
I purchased a fuel pressure tester from HF for the 100# gauge. $9.95
Removed the 30# gauge and installed the 100# gauge in its place.
Now it works as I like.

The right hand gauge is "% leak" - no pressure identified? Does not sound like the same set?

When I hook everything up the instructions say to adjust the pressure adjustment screw so the % leakage is at zero - where it stays? Should I not connect some part of it up when adjusting teh pressure? Something in my sequence does not make sense?

Vance,
You set it up disconnected to read zero leakage. That is the compressed air is at the inlet, however there is no air leaking out since it isn't connected. You then make the connection to the hose going to the cylinder.
The problem I had with this is the test pressure is 30#. You can see this at setup. The left input gauge reads 30# when the right side gauge is fully pressurized to the zero leakage position.
Once connected to the cylinder the right gauge pressure drops in response to the leakage in the cylinder.
My problem was the test is conducted at 30#.
I prefer the industry standard at 100#. Thus the switch to a 100# gauge.
With the 100# gauge you get a direct readout.
For example if the right gauge reads 96#, then it is 4% leakage. 90# is 10% leakage.
Since you mentioned you could hear air at the oil tank, that would indicate leakage past the rings.
To confirm this, retest after squirting some oil into the cylinder. I sprayed WD-40.
Rotate the engine one or two turns, then retest.
If it is rings, the right gauge pressure will show less leakage, that is the pressure at the right gauge will show a higher pressure with the second test.
It will all make sense once you think about it.
Good luck,

Vance,

The instructions aren't that good.

Set the compressor pressure to around 60 pounds.

Connect the tool. Now adjust the knob to zero the right-hand gauge. Give the tester a tap or two to eliminate the friction in the movement, reset to zero.

Air pressure in the left hand gauge should be around 35 psi? It doesn't matter as the percentage relationship is what's important.

NOW connect the hose to the cylinder through the quick disconnect fitting. The percentage of leakdown should read on the right hand gauge.

http://forums.pelicanparts.com/uploa...1112536862.jpg

If you have a high reading it's entirely possible that the engine is NOT at TDC on compression. Rotate the engine slightly, and I mean by a single width of the timing mark on the pulley, either direction and note the reading on the gauge. In my case, last weekend I saw 20% and then moved the engine slightly and got 4%. Just one of those things.

Good luck!

I was speaking about a commercial unit. I don't have a HF unit. The principle is to measure the difference between the charge and what pressure is maintained. During the test, there will be a flow of air. If it's enough flow, you will be able to hear it in the exhaust, intake or crank case breather (if you put a stethoscope type of thing in the breather).

People use 100 pounds on the charge and read the maintained pressure on a 100 pound scale only to make the math that simple. 95 pounds maintained with a 100 # charge is 5% leakdown. You could lower the scale to where ever you want as long you don't expect reliable results at 10 or 20 lbs. 100 lbs. pushes its way past worn parts for a better reading.

I could oil up a cylinder through the intake, spin it a few times and use a low pressure to make you believe that that cylinder is better than it really is. 100 # will blow that oil aside, no faking. But do it dry and do it on a warm engine and I'll wager 50 # charge would be enough.

I can't answer you question about the zero adjustment, but maybe if you understand the goal here, it will become clear as to how to use the thing.

Johns right , our unit (shop) looks like that so it may be HF . It is around 35 psi to set the unit to Zero .

It must be zeroed to work properly .

John - Thanks! It is the timing of connecting it up the the cylinder that I missed. Now that makes more sense. Zeroing it out after it was connected did not!

Milt - Understand the 100 now.

Thanks guys. I got it figured out and measured it cold with a leakage of 32%! Zeroing out was a PIA - that is setting teh pressure so the % leakage is at zero. The pressure was only about 15%. Need to do it hot and see what I get. It is a rebuilt motor and I have concerns the rings are not sealing - does not look good!