Leak Down Testing - Help Options

[vesnyder]

I am trying to understand how to use my new leak down testing tool from HarborFreight. I am trying to see if my rings are sealing on my rebuilt motor. 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!

[brant]

I don't quite understand your question

do you mean your intake pressure is 12psi?
most of the guages work at 100psi
(I have seen 50psi ones, and then you double your results to figure leakdown)

so the motor needs to be hot
pull the plugs 1 at a time as your doing that cylinder
turn it to tdc for that cylinder before pulling the plug.
(the reason is that if you were to drop a bit of carbon as you pulled the plug, the valves would be closed for that cylinder already and eliminate the chance that the bit that dropped could get under the valve)

incoming air at OVER 100psi
crank the incoming air down below that
(failure to do so can damage the guage)
install guage.
crank air up to 100
see what 2nd dial reads for leakdown numbers

that should do it
oil filler would be rings.
exhaust would be exhaust valves
carbs would be intake valves
brant