I am having an issue with my 2011 c-70. It was squealing and building crankcase vacuum all the signs of a ruptured diaphragm in the pcv system. I replaced the oil filter module which has the diaphragm In it. However I still get the squealing and building vacuum in the crankcase however not as much as before.

 

When the PCV is working correctly., you will feel a slight vacuum when you take off the oil cap while the engine is running (I do this weekly to ensure the PCV membrane hasn't ruptured). If feel pressure coming out of the oil cap, then you have a problem.

 

a professional shop will use a vaccuum gauge to see if your crank case pressure is within spec. Normally the problem is when there's positive pressure (ie clogged PCV/ports which don't allow the intake to pull the vacuum). What happens when you pop up the dipstick? (to allow a vent) does the sound change?

 

Yes, you will hear a change in sound. When you pop out the dipstick, you're releasing the pressure inside the crankcase. Pulling the dipstick out a little is a trick to use if your PCV membrane has failed or if the port connecting the oil filter housing to the engine has clogged.

 

I was just wondering if this was resolved. I have a 2008 C70 with the same issue and I was going to replace the oil filter housing and now I'm wondering if this won't resolve the problem.