Compression and Leak Down Tests
 

Hey everybody, I did a cold compression test on #4 and it came back at 150, which according to everything I've researched is VERY low. So I then did a leak down test, but that came back with almost no leakage at all.


I'm also not having any smoke, CELs or rough idle. So is 150 ok? Car has 55K on it.



Thanks

What were the results from the other three cylinders?

And why are you performing a compression test? Are you having some sort of issue?

Didn't get to the others yet, probably tomorrow. And I'm just testing to see if engine is healthy enough for supercharging.


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Gotcha. Yeah, the best thing to do is get data from all four cylinders before coming to any conclusions.

OK, did compression tests on 1-3 and they all came back an even 150psi give or take a couple PSI. Also did a leak down test on #1 and it came back good, about 2-3%

I also tried a different gauge in case that was the issue and that came back 150 as well.


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I sent an email to my tuner shop who does Subaru's all day long, this is what they said:


"In general cyl to cyl consistency is the most important. If leakdown is that low and all cyls are similar I wouldn't worry about it"

Leak down/compression tests are good for troubleshooting issues and getting an idea of health if you do not know the engine. If you know your engine you are better off going by how it runs and controls the oil. AKA does not burn a lot.