leakdown PSI?

[Alan Goettel]

I am doing a leakdown test on a 964 3.6. Test kit has no directions. What pressure should I send through regulator?

thanks,

[911nut]

The kit I have at work says 100 psi. Problem is that I only get 80 psi building air

[Flat6pac]

The one I have, Snap-On,requires 30#
Bruce

[staffanbe]

I used 50 psi on my 964 turbo.
See more here: Rebuilding a 964 3.3 turbo

[OldTee]

Use math here. 60/80 = 75% / 75?100 = 75%. You would hope for 90% or so.

[JFairman]

You zero the right hand gauge with the built in air pressure regulator. Thats your working pressure when doing the leakdown test, and different leakdown testers will be different...

100psi would be best because that will help seat the top compression ring and each pound the right side gauge needle drops under the 100psi zeroed starting point wil be 1% leakdown.
As an example of different leakdown gauges, a harbor freight leakdown tester I have zero's out the origonal right side leakdown gauge at about 13psi. I tried two of them and they were the same.

There are uses for testing at that low a pressure, like testing for leakdown with the piston halfway down the cylinder or anywhere in between during the power stroke while trying to hold the crankshaft from turning with a wrench, but 100psi at TDC is all around better.

It's simple to unscrew the right side gauge from the harbor freight tool and screw in an inexpensive 100psi gauge in it's place so you can leakdown test with 100psi air pressure in the cylinder.

The left gauge tells you how much air pressure you are setting the regulator to while zeroing the right hand leakdown gauge.

There is a tiny air orifice in the body of the tool in between the two gauges that the air has to go through during the test...