Leaks vacuum.

 

And now you know!! Thanks!

 

On a typical car, the intake system is under vacuum with a pcv valve pulling crank case pressure out......back into the intake

On this car. The entire oil system is under vacuum......and the intake system
The oil cap
The dip stick even has a seal on it
If you get a valve cover leak, oil pan leak, or even a front oil seal......you have a vacuum leak. A lot of people bypass and run into a catch can on here. This takes the oil system off of vacuum but you have to empty the can once in a while.

I'm not sure how often

 

A lot of people bypass and run into a catch can on here. This takes the oil system off of vacuum but you have to empty the can once in a while.

Actually the the only think the oil catch can does is not drain back into the crankcase. Also the way many set up the OCC they end up with too much/more vacuum in the crankcase and this can actually cause more issues.

 

I replaced my oil filler cap a while ago. Can't remember why. Anyway, the new Genuine BMW filler cap sealed noticeably tighter than the original.

 

This is good info.

Curious side note: When you buy new ones do they still say Castrol?

 

This is good info.



Curious side note: When you buy new ones do they still say Castrol?

I think so. Check the picture on ECS Tuning website to be sure.

Here's a pic of the undersides, new on top:

 

Mine looked like the bottom one in that pic^ but worse before I did my CCV so I picked up a new cap.

 

With so many threads on the oil catch can.

Is there a correct way to set one up to retain vacuum the way the e46 likes.
The ccv usually lasts a while so I just replace it. It's not that hard with directions the first time out and it lets you clean and check the icv and the lower intake boot.