Compression and Leak down Results

[elrichmeister]

Last month made a post about if there is a way to find out if i had a tune, using a octane booster removed some pinging i was hearing.

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/366978-is-there-a-way-to-find-out-if-a-car-has-a-tune

It was mentioned to get a leak down test to determine if I had head gasket issue.

I finally had some time to schedule a compression and leak down test at a shop. The results kind of worry me based on some searching if done on this forum and other sites. However the shop said the results look fine and shouldn't worry too much about it.
They mentioned that they couldn't reproduce the pinging noise, and that may be because there is still some octane booster in the fuel. I did fill up with about 10 gallons of 91, so there should less of it by the time the shop had the car.

So here are the results:

Compression Test:
1. 160psi
2. 150psi
3. 155psi
4. 170psi
5. 160psi
6. 160psi

Leak Down:
1. 10%
2. 10%
3. 5%
4. 5%
5. 5%
6. 15%

I did order a compression test kit that ill try on my own once i receive it to confirm findings above

https://www.amazon.com/dp/B00SKSAB8U

Leak down value on cylinder 6 worries me. Other than that the car works great, no codes no misfires.

[Slideways]

Did the shop remove all the spark plugs before doing the compression and leak down test?

[elrichmeister]

Did the shop remove all the spark plugs before doing the compression and leak down test?

Honestly not sure, i think its pretty common to remove all of them?
Been looking at the actual procedure and from what i saw, the engine should be warmed up, all spark plugs out, and the throttle needs to be pressed all the way down when turning the engine.

One thing, i think its good that all compression values are above 150psi, and there is no extreme differences.
Maybe I'm worrying for nothing, and keep using octane booster to keep the car from making the pinging/detonation sound. I have to really lug it in like 3rd/4th gear on a hill to get it to make the sound when running on 91 octane.

[Slideways]

Honestly not sure, i think its pretty common to remove all of them?
Been looking at the actual procedure and from what i saw, the engine should be warmed up, all spark plugs out, and the throttle needs to be pressed all the way down when turning the engine.

One thing, i think its good that all compression values are above 150psi, and there is no extreme differences.
Maybe I'm worrying for nothing, and keep using octane booster to keep the car from making the pinging/detonation sound. I have to really lug it in like 3rd/4th gear on a hill to get it to make the sound when running on 91 octane.

You'll want to ask them. Since the S54 headgasket breaks between cylinders, all spark plugs need to be removed while performing the test. I have seen a few videos where the person leaves the spark plugs in other than the cylinder they are testing.

As an example, here is a S54 compression test with all but one spark plug installed:

All cylinders between 150-165psi

Compression test with all spark plugs out

Cyl 1-6 - 130psi, 110psi, 130psi, 150psi, 150psi, 150psi

Pinging below 3k RPM, high load, high gear and no misfire codes. Leak down confirmed it because you could hear air escaping from an adjacent cylinder with the spark plugs out. Turns out the gasket was completely broken between all cylinders except for cylinder 4 and even then, with the headgasket being 3 layers, the middle layer was broken on one side of cylinder 4.

DME doesn't seem to detect a misfire until the cylinder reaches less than 90psi or something like that. Other than the pinging and slight power loss, it'll drive perfectly fine. I suspect there are quite a few high mileage S54s out there with bad headgaskets and owners are completely unaware.