Compression test vs. Leakdown test
04-09-2002, 05:23 PM
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Compression test vs. Leakdown test
First let me make sure...
compression test --> crank engine to build compression, then reads how much compression, right?
leak down-> you bring the engine at TDC so all the valves are closed. then it injects air into the cylinder. based on how much air it can keep pushiong through it tells you what percentage of leakage engine has. then you check where air is leaking from to diagnose the problem.
Now if this is the case, what is the advantage of a compression test? Realistically both will tell you how much the engine is leaking (by way of low compression reading on a comp. test). The leakdown test allows you to trouble shoot the leakage though, so what is the point of a comp. test all together? Is it easier to do? Cuase I remember the setup being similar for both tests.
can someone give an example of soemthing a comp. test could detect that a leakdown cant? Only thing I can think of is a seized piston that doesnt leak becuase of a broken rod or something. Does this seem right?
-jordan
compression test --> crank engine to build compression, then reads how much compression, right?
leak down-> you bring the engine at TDC so all the valves are closed. then it injects air into the cylinder. based on how much air it can keep pushiong through it tells you what percentage of leakage engine has. then you check where air is leaking from to diagnose the problem.
Now if this is the case, what is the advantage of a compression test? Realistically both will tell you how much the engine is leaking (by way of low compression reading on a comp. test). The leakdown test allows you to trouble shoot the leakage though, so what is the point of a comp. test all together? Is it easier to do? Cuase I remember the setup being similar for both tests.
can someone give an example of soemthing a comp. test could detect that a leakdown cant? Only thing I can think of is a seized piston that doesnt leak becuase of a broken rod or something. Does this seem right?
-jordan
04-09-2002, 06:25 PM
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Re: Compression test vs. Leakdown test (Jordan_4WS)
compression test is really really easy to do with a $25 gauge and the spark plugs out. leakdown isn't hard, from what i read/hear, but it certainly isn't AS easy!
04-09-2002, 08:47 PM
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Re: Compression test vs. Leakdown test (schwett)
They are both pretty simliar in process. I suppose leakdownn is more work but not really. I have done both test to a Chevy 305 on a stand... Never done one to a motor in a car.
-Jordan
-Jordan
04-23-2002, 02:39 PM
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Re: Compression test vs. Leakdown test (Jordan_4WS)
For leakdown you have to figure out how to hook up your compressor to your engine, then you have to take your valve cover off to listen for where the leak is. this is not as easy as a compression test.
04-23-2002, 02:58 PM
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Re: Compression test vs. Leakdown test (CRX7)
For leakdown you have to figure out how to hook up your compressor to your engine, then you have to take your valve cover off to listen for where the leak is. this is not as easy as a compression test.
I found out the reason you do both is cause if you have a seized piston or seized valve, you will not be leeking, but you will have low compression.
-Jordan
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