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Discussion Starter #1
Hello, I just got the numbers of the "leak test" compression test for my new V8 lotus. The compression appears to be good, can anyone shed some light on this data?

Thank you

Cyl 1) Compression 130 Leak 30%
Cyl 2) Compression 135 Leak 25%
Cyl 3) Compression 135 Leak 25%
Cyl 4) Compression 130 Leak 30%
Cyl 5) Compression 125 Leak 35%
Cyl 6) Compression 125 Leak 35%
Cyl 7) Compression 135 Leak 25%
Cyl 8) Compression 130 Leak 30%

I am not sure of these numbers, compression seems fine? Can anyone let me know if these are decent readings? Thank you
 

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Where do you live, at what altitude?

THe spec is 155 psi +/-15psi at sea level, but you are allowed lower compression if you are testing at higher altitude.

Was this done with a warm engine and the throttle held fully open?

Did you put a little oil in the cylinder to see if the leakage was past the rings or the valves?
 

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Discussion Starter #5
Test done at british motor cars in california car has 27k miles not sure how the test was done
 

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The spread at 10# is fairly tight meaning the valves don't have any major problems, I think the leak down at 25 -30%, for only 27,000 miles, seems high and relates somewhat to the low absolute pressure levels. This seems to indicate a ring sealing problem. I would have tried a little oil (like Travis suggested) to see if the absolute pressure comes up and leak down goes down.
 

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even though the compression numbers seem low and the leak down % seems high, I think it must be either the test procedure or the test equipment. All the cylinders are very similar to the others. Usually, if you have a problem, it shows up in individual cylinders. You wouldn't have compression or leakage issues in all the cylinders.

BTW, I once owned a Harbor Freight leakdown tester.......it showed 30% leakdown for everything. lol!
 

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tell you what --- summer time and you should enjoy the car!!
i know you are looking for comfort and baseline --- the compression is very very good!!!
enjoy!!
 

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The #'s are a little low for the mileage. It could be due to the motor not being used much recently (I don't know the history so I am just guessing). Cars being sold are usually driven all that much. I would run the car and recheck. Do it twice, once without oil and once after adding a little oil and cranking the motor. If the motor is close to being due for an oil change that might improve the #'s too. Oil won't change the leak-down much but if it improves the compression you know the rings are worn and that is what I am guessing is the reason the compression is a little low. More important is the history of the timing belts. I would change ALL of the fluids unless you KNOW for SURE when it was done last and what was used. As far as the leak-down and compression #'s, the most important thing is that they be close and they are. It shows that although the engine is a little worn (and that is to be expected) everything is wearing evenly. If the battery is over 5 years old it should be replaced and the tires if over 10. Again, check on those timing belts and then go have fun with the car!
David Teitelbaum
 
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