Leakdown tester

[Brent 930]

I would like to get a leakdown tester so I can do it myself. Anyone know of a good source for one that works well with the 930 3.3L engine?

Thanks

[Grady Clay]

Brent,

I have two old Sun Electric Corporation cylinder leak testers that have worked perfectly for more than 35 years. They currently agree with each other to as good as the resolution will allow and agree with other current testers. They are Model 228 and I think Snap-On bought the rights or currently markets it. You can reliably differentiate less than 1% when close to zero and it is very repeatable. It is direct reading; no calculations are necessary. The best part is it is very easy to use so I can get multiple measurements quickly. I made my own tool to screw into the sparkplug hole that fits a 911 just right.

I think this is the single most useful diagnostic tool for a 911, not the only, just the best.

Best,
Grady

[Zeke]

If you google 'leak down tester,' there are several to consider.

[1974carrera]

I've used my Tavia leakdown tester for quite afew years and really like it. I think I purchased it from Eastwood...maybe Pelican can supply it. Here's a link to the Tavia page...just scroll down to see it. Note they have quite a few different hose assemblies with a variety of fittings available.

http://www.tavia.com/cat8.html#3

I guess I should add that I have never used mine on a 930 3.3L, but I can't imagine why it wouldn't work.

[Brent 930]

OK, I got one but I need a hard extension so I can tighten from outside the valve cover. Where do I get one?

Thanks

[Grady Clay]

Brent,

Here is my homemade adapter. It measures 19.8 cm from the head sealing surface (not counting the sparkplug washer to the underside of the 20 mm nut. The OD of the tube is about 15 mm. All the joints are brazed. You can run a cleaning brush up from the engine end to insure cleanliness.

The next one I make will have a 20.6 mm (13/16") nut, designed so the regular sparkplug socket wrench fits.



Best,
Grady

[devo230]

Which years is a leak-down good for? I heard that it's not effective models that develop oval cylinders at the top of the stroke/cylinder. A service manger told me that an official for Porsche USA (I may have this wrong) supported leak-down testing in the past, but now he now thinks that the old style compression testing is more reliable. Please correct or elaborate.

I've also heard that compression testing can be controlled for results and that it also can generate incorrect results if not done incorrectly.

Thanks.

[ChrisBennet]

Originally posted by Brent 930
OK, I got one but I need a hard extension so I can tighten from outside the valve cover. Where do I get one?

Thanks

I use my Tavia through the valve covers but it's was a PIA until I made a "splint" out of some tubing to stiffen and straighten the part of the hose that goes though the valve cover.
-Chris

[Grady Clay]

Devo230,

The Cylinder Leak Test and Cranking Compression Test are valid engine tests for any engine from 2-stroke moto to aircraft. These tests are comparative, meaning you should perform them when everything is OK with your engine and you can compare your test results with others.

Of course someone can improperly skew the results. That is part of the DIY philosophy, you don’t fool yourself.

Best,
Grady

[1974carrera]

[B]Brent[B],
I do the same thing that Chris suggested...just "splint" the hose that Tavia supplies so that the hose is straight enough to insert and engage the spark plug hole. The hoses Tavia supplies use an o-ring to seal to the head so it doesn't require much torque to adequately seal the hose.

Grady
I like the adapter you made. Did you gut and remove the ceramic from an old spark plug and then use the remaining threaded metal base to construct your adapter?

[Brent 930]

Thanks guys

[Grady Clay]

Bob,

I think I made this tool in 1969.

Yes, it is one of those very specialized and previously 911 tested ones – called a used BP8ES. Actually any plug will do. A metal lathe makes easy work of all this. I enlarged the bore of the sparkplug piece to match the ID of the tube for easy cleaning. Note the taper on the first few threads for easy starting.

Every now and then I replace the sealing gasket. Keeping the bore and threads clean is very important.

My next iteration will use the hex off a sparkplug on the outer end and turn the hex off the air fitting and braze it in place so a standard plug wench fits. Next time I’ll also silver solder rather than braze – much nicer results. Sending it off with engine hardware to be plated would be a nice touch.

This tool also fits one of my cranking compression gauges.

I have a shorter version for 356/912 with a ½” reach plug.

Best,
Grady

[1974carrera]

Thanks for the description, Grady...and the 2nd gen ideas too. I have a few engines with deep plug wells or access, as well as different plug diameters, so I think I'll make up a couple. I haven't had any problems when turning the the leakdown adapter hoses to tighten their fitting in the plug hole, but I've never liked doing it. With your tool design, I'll make up a hose with quick releases on each end and I'll be good to go. I always enjoy making new tools anyway!

Thanks again for sharing your ideas.

[aigel]

Go to the news stand and buy this month's Car Craft magazine. It has a lenghty article about leak down testers, different brands, how to use, pros and cons.

George

[911pcars]

If you have a compression tester with a removeable hose (see below), you can use that to attach to the leakdown tester.



Sherwood

[Grady Clay]

Bob,

I agree with you 100%, I also never liked the hoses and that was what inspired me to make these adaptors. I only used the hoses in situations where it was necessary (928, Ford 460).

This tool fits 547, 692, and 587 just fine.


George,

I just cruised by Tattered Cover (largest bookseller in the Mountain West) with almost 200 auto periodicals and no Auto Craft. Can you scan and post the article you referenced, “fair use.” I would like to critique it.

Best,
Grady

[turn6]

U might find what you're looking for at carcraft.com just do a search for leak down testers

[aigel]

http://carcraft.com/toc/

You got to be joking, that they do not stock that magazine?

[aigel]

Grady:

I don't do scans. Send me your mailing address via PM and I will send you a copy by snail mail.

George

[ChrisBennet]

Originally posted by 911pcars
If you have a compression tester with a removeable hose (see below), you can use that to attach to the leakdown tester.



Sherwood

I wish I could! My leakdown and compression gauges have the same connectors but for some reason I get screwy readings if I use one hose on the other gauge. I forget why, maybe a check valve in one and not the other? When I'm doing a compression and leakdown I have to screw/unscrew a hose twice as much as I would if I could share the hose.
-Chris