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Old 09-11-2012, 12:56 PM   #1
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Default Compression/ leakdown on engine stand

I bought a '99 1.8 liter engine a few months ago. It was said to have overheated and needs a head gasket. The engine is complete minus flywheel, starter, balancer, blah blah blah. Its a complete long block, and I can spin it over and watch the valves opening and closing. Sounds ok to me.

It is bolted to an engine stand in my garage and I'd like to do a compression / leakdown test on it. How will I hold the crank still to perform the leakdown? How do I spin the engine over to do a compression test?
Very noobish questions, I know, but I just want to see where this motor is at just for ***** and gigs before I tear it apart.
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Old 09-11-2012, 12:58 PM   #2
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I'll install it on my car and let you know...
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Old 09-11-2012, 01:06 PM   #3
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Both test should be preformed with a warmed up engine but results on a cold engine should give you a good idea of it's health.

compression test requires the tranmsission and starter to be attached. then just hot wire power from a battery to the starter. It's easy but the engine would probably need to be removed from the stand.

Leakdown test can be done on the stand. The cylinder should remain closed at TDC during the test. If not just dial down the PSI some. Its just a leakage percentage.
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Old 09-11-2012, 01:08 PM   #4
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Can you bolt on an FM crank bolt tool with what you have?
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Old 09-11-2012, 01:13 PM   #5
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Starter?? How about an impact gun??
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Old 09-11-2012, 01:17 PM   #6
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yes
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Old 09-11-2012, 01:23 PM   #7
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I was thinking impact for the compression test, but with leakdown, the engine needs to be locked in place. I'm thinking with 100psi going against a piston, that gives it enough force to move the car...I wouldn't be able to hold it with a wrench and my arm when its bolted to my stand. Perhaps I can make something that bolts to the crank and it keeps it from spinning?
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Old 09-11-2012, 01:23 PM   #8
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Quote:
Originally Posted by thirdgen View Post
Starter?? How about an impact gun??
If you can get the rpm up to the equivalent of a starter it should work I guess... do a little reaserch because Ive never tried it personally. Interested to see how this turns out.
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Old 09-11-2012, 01:26 PM   #9
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Perhaps I can make something that bolts to the crank and it keeps it from spinning?
a 21mm socket and a breaker bar, and you pushing against it.

why do the rpms need to see the RPMs that the starter can produce to read compression?
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Old 09-11-2012, 01:36 PM   #10
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a 21mm socket and a breaker bar, and you pushing against it.

why do the rpms need to see the RPMs that the starter can produce to read compression?
It doesn't need to be eaxcct but in the same ball park. Turning an engine over with a ratched wrench at 30 rpm won't give you great presuure reading. some of the air would leak out at a slow piston velocity before it reaches TDC so the pressure won't be as high. Most baseline compresison numbers are with a starter so that eliminates that variable when determining engine health.

Then again it may not make that big of a difference and Im just a noob so don't listen to me.
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Old 09-11-2012, 01:39 PM   #11
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okay, ill buy that.
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Old 09-11-2012, 01:50 PM   #12
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I've done a simple compression test on a stand. Cranked it by hand, too. You just have to keep turning it over until you get the gauge up. We made a handle to go on a large breaker bar, and spun it like we were trying to start a model A. Believe me, my arms were like lead after that, but we got the readings.
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Old 09-11-2012, 02:18 PM   #13
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I figure as long as you do the test consistently, you could at least read the difference in numbers and ignore the actual results.
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Old 09-11-2012, 02:27 PM   #14
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Why even bother with the compression test when the OP is going to leak down test anyways??
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