[Jonjt]

Folks,
I recently did a cold compression and leak down test on my N54. The results are below:

Compression
1: 150psi
2: 100psi
3: 100psi
4: 115psi
5: 115psi
6: 145psi

Leak down:
1: 90psi at 90psi, audible leak
2: 85psi at 90psi, audible leak
3: 85psi at 90psi, audible leak
4: 90psi at 90psi, audible leak
5: 90psi at 90psi, audible leak
6: 90psi at 90psi, audible leak

I suspect that the compression tests were so unusual because the engine was cold. The results of the leak down test seem to further suggest this. At this point, I'm nearly ready to fix/service the car for another ~2 years of use, but I wanted to verify my suspicions before going forward. Are my conclusions correct?

Thanks,

[Dave92N54]

Those seem fairly low to me

I believe our's should be 150-200 on all cylinders

I recently did a cold test, 131k miles
cylinders 1-3: 179psi
cylinder 4-6: 180psi

I'd see if you could try a different tester? or retest, equipment may have been leaking

[Jonjt]

Originally Posted by Dave92N54

Those seem fairly low to me

I believe our's should be 150-200 on all cylinders

I recently did a cold test, 131k miles
cylinders 1-3: 179psi
cylinder 4-6: 180psi

I'd see if you could try a different tester? or retest, equipment may have been leaking

I was thinking about trying a different pressure gauge and different air hoses. Which compression tester did you use?

I have 135k miles, by the way.

[Dave92N54]

I have a compression tester from Innova, part number 3612. Should be able to find it at most local auto parts stores.

[Jonjt]

Originally Posted by Dave92N54

I have a compression tester from Innova, part number 3612. Should be able to find it at most local auto parts stores.

The design seems to be the same as the one I have. The only obvious difference is branding. I think it's better to try testing the engine hot than to buy another compression tester.

The engine makes good power, so I think a warm test would show more reasonable compression numbers.

[Mustafa.e92]

My engine made 170 through all cylinders cold. 160,000 kms

[dpaul]

Originally Posted by Jonjt

Folks,
I recently did a cold compression and leak down test on my N54. The results are below:

Compression
1: 150psi
2: 100psi
3: 100psi
4: 115psi
5: 115psi
6: 145psi

Leak down:
1: 90psi at 90psi, audible leak
2: 85psi at 90psi, audible leak
3: 85psi at 90psi, audible leak
4: 90psi at 90psi, audible leak
5: 90psi at 90psi, audible leak
6: 90psi at 90psi, audible leak

I suspect that the compression tests were so unusual because the engine was cold. The results of the leak down test seem to further suggest this. At this point, I'm nearly ready to fix/service the car for another ~2 years of use, but I wanted to verify my suspicions before going forward. Are my conclusions correct?

Thanks,

Compression testing is notoriously variable and good mostly for revealing a catastrophic problem. Leak-down gives a much more nuanced picture of a problem. The place where the "audible leak" is detected (i.e. exhaust, intake, crankcase breather, coolant tank) can tell you a great deal about the nature of the problem.

Although I'd start with a higher pressure (at least 100psi), your leak-down shows an incipient problem with cyl 2 and 3, perhaps not coincidentally the cylinders which fared worst on the compression test.

Typically, a new engine should have a leakdown of not more than 3-5% (95-97psi registered on 100 psi input). At 10-15% a rebuild should be planned. You're at 6% on cyl 2 and 3; probably fine for now.

[Jonjt]

Originally Posted by dpaul

Compression testing is notoriously variable and good mostly for revealing a catastrophic problem. Leak-down gives a much more nuanced picture of a problem. The place where the "audible leak" is detected (i.e. exhaust, intake, crankcase breather, coolant tank) can tell you a great deal about the nature of the problem.

Although I'd start with a higher pressure (at least 100psi), your leak-down shows an incipient problem with cyl 2 and 3, perhaps not coincidentally the cylinders which fared worst on the compression test.

Typically, a new engine should have a leakdown of not more than 3-5% (95-97psi registered on 100 psi input). At 10-15% a rebuild should be planned. You're at 6% on cyl 2 and 3; probably fine for now.

Thanks for the information. I had to rent a compressor, as I didn't have one that could supply the needed pressure. The rented compressor was a small, 2 gallon unit that was constantly running in order to maintain pressure. I suspect that if the compressor I used was larger, the differences between pressure input and steady state pressure would be larger.

[slanteyez]

No point in doing it cold. Warm it up and check it from there. As long as the numbers are consistent throughout the cylinders, send it. Those leakdown test numbers are fine.