Well looked around all day for a place that sells a leak down tester and only found that Napa sells it for $110. I wasn’t about to pay that so I want to home depot and bought all the fittings and made my own, what do you guys think?

looks great !

In case anyone else is tempted to do the same http://www.xs11.com/tips/misc/misc3.shtml

After looking over this design I can not figure out how it will work. You need a way to pressurize the cylinder then cut off the air supply to it and measure the loss. With that design there is constant pressure to the cylinder, there is no cut off valve.

The female disconnect keeps the gauge portion sealed until you hook it to the hose going to the cylinder. You adjust the regulator for whatever pressure (he specifies 100psi) and then hook it to the cylinder....the .040 orifice serves as a restrictor to control the airflow and the gauge reads how much pressure the cylinder will hold at that given flow rate. Higher pressure equals less cylinder leakage.

Open valves will show near 0 psi and a good sealed cylinder will be in the 90+ psi range (using 100 psi feed.)

Right, sealing it up and then watching the pressure bleed off doesn't really tell you much.

Oh okay, I get it now. I guess opening the valve slightly would be too inaccurate, so I will have to figure out some way of making a restrictor.

EDIT: The smallist drill bit i could find was 1/16 = 0.0625 = ~1.588mm, do you guys think it matters that much if it is not .04?

A bigger hole will make it less sensitive. It'll probably still be good for burnt valves and what-not, but really slow leakage like through a borderline head gasket may be a little harder to see.


For really small bits, try looking in the Dremel section. they have some pretty tiny ones sometimes.

In the dremel section I found a 1/32 and 3/64 drill bit.
1/32=~0.031=~0.79 Millimeters
3/64=~0.047=~1.19 Millimeters

So the question is which drill bit to use? Anyone have a suggestion?

Either one would probably be close enough. Try a hobby store though, they have all kinds of tiny drill bits.

Where did you get the spark plug fitting?

KD Tools P/N 901, includes 14mm and 18mm spark plug to 1/4" NPT adapters. Costs about $5. Or you can use a P/N 2992 which is the same thing in a 14" hose. I'm sure there are other sources as well.