Leakdown tester: building your own

Tips and Recommendations from Guru Mike Nixon

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mikenixon
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Leakdown tester: building your own

Post #1 by mikenixon » Sat Jan 12, 2019 5:52 am

Inexpensive, ready-made leakdown testers are easy to find today -- you don't have to mortgage your house to a Snap-On dealer. Motion Pro has a fairly good unit.

You can also make your own. Here's the rundown:
Pressure regulator . This is an automotive paint spray gun part. Grainger's is probably the cheapest, followed by Sears and Ace Hardware. EBay too. The 0~160 gauge that often comes with these regulators is, unfortunately, the wrong kind for our purposes. So we'll need to replace it with a 0~100. See below. Also, make sure your regulator comes with the block-off plugs for the two passages that you won't be using.

Pressure gauge. Get a quality, back-mount, 0-100 psi gauge. For the professional touch, carefully pry off the bezel and cover the faceplate with a new label. If you don't feel like re-labeling the gauge, no big deal. But you'll then have to read the gauge backwards; i.e. "10" would mean 90% leakdown. Not an intuitive way to use the tool. Better to relabel.

Spark plug adapter. Start by by clamping an old NGK spark plug in a vise (protected with wood or aluminum stock) and whacking off the porcelain with a well-aimed lateral hammer blow. Then grind or machine off the rolled-over seal above the hex, grind off the ground electrode, put the plug back in the vise and drive out the remaining porcelain with a drift. Tap the hex end with a 1/4" pipe tap. Screw the bugger onto a 1/4" to 1/8" pipe reducer, and that onto a 12" grease gun hose. Use pipe-sealing tape on all threads. Make a separate complete hose assembly for each engine you're going to test that has a differently-sized spark plug hole.

Damper valve. This essential part damps the gauge's needle movement. It's merely a restriction between the regulator and the gauge. The easiest way to make it is to fill the middle pipe with epoxy and afterward drill through it a 0.040" (#60 or 1mm drillbit) hole. You could also machine a tight-fitting plug and drill it.

Image

Parts List
Miniature air pressure regulator
0-100 psi gauge, back-mount, metal case, removable bezel
12" grease gun hose
1/4" NPT quick disconnect fittings
1/4" plumbing pipe and "T" joint
1/4" to 1/8" NPT reducers (2)
Old spark plug
Teflon plumber's tape

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gltriker
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Re: Leakdown tester: building your own

Post #2 by gltriker » Sun Jan 13, 2019 1:38 am

Recommend folks scroll down this page to SIMILAR TOPICS, too to further understand the importance of this diagnostic tool. tumb2

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mikenixon
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Re: Leakdown tester: building your own

Post #3 by mikenixon » Sun Jan 13, 2019 5:58 pm

Thanks, gltriker!

By the way, a notice to all:

I feel compelled to mention -- I originally wrote this article, including the drawing, when I first established a website back in 1997. It was virtually my first online article. I say this because several websites have copied it word-for-word, none with permission and only one with attribution. Even the drawing! If you see it or the drawing elsewhere, now you know. :)

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gltriker
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Re: Leakdown tester: building your own

Post #4 by gltriker » Mon Jan 14, 2019 1:29 am

Highly Recommended reading materials. :oldies

https://www.motorcycleproject.com/index.html#100

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Re: Leakdown tester: building your own

Post #5 by sunnbobb » Thu Jan 17, 2019 2:47 am

Nice, thanks man.


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