DIY Leak Down Testing?
 

I posted this in Engine Rebuilding and got no responses, so trying here. Sorry if this has been asked (I'd assumed it would have been) but I couldn't find anything after performing a search. If there is a thread, please post the link.

I'm looking at trying to DIY leak down tests. Some of the places where used 911s are located don't have reliable shops nearby, so hence the need for a DIY test.

Seems like a dual gauge tester would be more accurate then a single gauge.

I've read a few articles for general leak down testing, but nothing specific for a 3.2 Carrera.

Specific questions:

Quality testers at a reasonable price?
Any specific order to follow?
Specific sequence?
Acceptable readings?
Paths of leakage to listen for?
Specific tools of the trade (stethoscope-type device, or ?)?
Ways to find TDC?

Any advice appreciated. Mahalos, gentlemen!

Ideas
 

Start Here. This is from the Technical Articles section.

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-2.htm

There are also posts on this subject in the 911 Technical forum under "leak down". This should get you started.

Bryan

Thanks for that info and link.

Any good leak down gauge recommendations?

Options
 

Harbor Freight is where I purchased mine for $35. You can get professional grade for around $80 or more but I have seen post's where people have put both gages together and they registered the same.

Go to HF and you should be fine. My .02 anyways.

Best of luck,
Bryan

I bought ight that leak down tester from Harbor Freight too. I haven't used it on the 911 but I have used it. You're not taking any really precise measurements with it so I don't think spending more money is going to make much of a difference. It seems to me that the leak down test is best used for pinpointing a problem that has already presented itself as pretty obvious (i.e., a compression loss that is creating a miss/loss of power).

the Harbor Freight one works. I have it. But beware -the instructions that come with it are incorrect!

As previously noted, buy a pro grade one if you need to know 10 or 14% leakdown. IE the HF one is good if you *know*you've got comp loss and are trying to pinpoint where the loss is coming from.

The rings have to be set in the lower part of the piston ring land.

I never turn engine back to TDC if I pass it when trying to set piston.


It's not unusual to get a bad reading on our air cooled engines when nothing is wrong. If that happens other measures are taken to retest.

I got my pro one (Longacre I think) off of ebay... I think I paid $50 shipped for it. I have compared the HF to mine in store. The only noticable diff is that mine has a lot nicer gages... I suspect, if you wanted to turn your HF one into a really pro one you simply need to put some nice gages on it...

*shrug*

My used one did well enough to detect 100% leakage :( I'll be using it again soon to check my rebuild :) In this market there should be a lot of weekend racers unloading some nice stuff... unfortunately for them :( You may be able to get a really nice part for not much $

Best regards,

Michael

buy one from Jeg's or Summit Racing. Their's are modest in cost and pretty nice. I spent $60 to $80 or so on mine and you can narrow down to +/- 1%. The gauges have better accuracy, which is important, I think.

Note, you are supposed to check the engine hot, from feedback I got, it was not helpful to do a cold leakdown. I think the data should be correlate-able, personally, but not so from some of the expert engine builders I solicited for advice when trying to evalute a used motor. In the end, I did not follow my own instincts and purchased a motor with bad (cold) leak down numbers and ended up having to rebuild it at great expense.

Doug

I loosen spark plugs that have ant-seize on them. They are just a little more than finger tight. Then I drive car for 5 miles.

You shouldn't take out normally tightened plugs from a hot engine or you can damage threads.

If you search in the 930 forum, I built my own.
Two gauges - preferably identical, that can read up to 100 psi.
Makes it real simple. Then I had to make an adaptor thing for spark plug hole, to get the air down - chopped up, ground out a spark plug for the base, then welded a special length of pipe to it, and tapped in a gas fitting for air hose in top.
Worked just fine.
Alan

I've taken cold and warm leakdown numbers on the same engine and really didn't notice the difference. Personally I'd rather do it cold. It's just a little more comfortable working around a cold engine. Plus you are really looking for a variance, not an exact number. JMHO.

Google in leakdown tester. Several hits on how to make one. I think I paid about $15 in stuff from home depot.