Vacuum testing from the dipstick

[S50Sinner]

Originally Posted by JFP in PA

Intake vacuum and sump vacuum are two entirely different things. The AOS in these engines throttle the high intake vacuum down to about 4-5 inches of water in the sump when the AOS is working properly.

If you manometer is digital, you should be able to switch from inches of Hg to inches of water with a click, and then retest the dipstick tube. Again, you can also smoke test the tube as well.

You are too early in the process to claim victory......

Thanks for the input, I did make sure to record my plenum vacuum as a separate figure from crank vacuum, just not sure what to do with that information.

I know what a normal vacuum measurement should look like in a normal car, and mine looked perfect, I'm just wondering if normal rules apply to the Boxster or if there's some unique M96 thing I should be looking out for.

Sadly, I have an analog manometer, so I can't measure crankcase vacuum with my current precision, so all I've got to go by is plenum vacuum. I know I have some crank vacuum because I can hear/feel the sucking when I remove the oil cap/dipstick, and I know it's not too much because the car has a small reaction to it.

Do you think I have enough information to go on, or do I need to get a more precise manometer? I thought people used crank vacuum because it's easier to measure than plenum vacuum, which is why I was excited to get a smooth plenum reading.