OTC Tool - Vacuum / Pressure Guage

Respected Members,I came across this information regarding the OTC vacuum gauge and have tested it on several vehicles at our workshop. Currently, we are collecting data by testing vehicles with varying mileage, both low and high.I have a couple of questions about this:

1. Is this method applicable to all engine sizes, ranging from 660cc to 3000cc gasoline engines?
2. If the PCV system  takes more than 10 seconds or longer to draw 3 PSI, should we replace the PCV valve & most probably check for air leakage?

If you have any additional advice or insights, please feel free to share.Thank you!PCV Valve Test For Crankcase Ventilation

1. Operate the engine at normal temperature and idle speed.
2. Remove the hose connected between the air cleaner and valve cover or oil filler/breather cap. Plug the oil dipstick tube to prevent an air leak.
3. Hold the vacuum gauge with the rubber universal adapter firmly over the valve cover hole or filler/breather cap opening. A good PCV system will draw a vacuum of 3 to 5 inches within 10 seconds.

I can't say I've done that specific test too many times, so it's tough for me to comment.

My first thought is that 3-5 inHg in the crankcase is quite a bit. On the engines I've tested this way, most crankshaft seals are squealing (sucking in air) before they get to 3 inHg. I don't know that you can damage anything with excessive vacuum? But I'm inclined to be cautious.

I've also seen a few examples of GM 2.4L LEA/LAF engines that will struggle to achieve 30 inH2O/2.2 inHg with a clean PCV orifice. That would technically fail the test, potentially leading someone to remove the intake manifold unnecessarily.

What has your experience been so far?

We don't remove the intake manifold; instead, we simply connect a hose to the breather pipe to create a vacuum.

So far, the readings are mixed. I'm currently collecting data on various makes and models. For high-mileage vehicles, it typically takes 12–18 seconds to draw 3 inches of vacuum, while some manage it within 6 seconds.

In our city, the PCV system remains one of the most overlooked components.

Next time i will upload short video or image.