[possible335i2008]

Hey have a quick question, I did an oil change a week ago and noticed my vacuum on my boost gauge is a little lower than it was before I did the oil change. The oil filter cap was really on the housing before I changed it and i have it torqued down, there is no oil leaking out. The car is making boost normally not overboost codes but the oil filter housing cap was really overtightened when BMW put it on, when I remove the brake booster tube after turning off the car I get the suction noise. I am just wondering where that extra mmhg of vacuum went? Perhaps my oil filter cap was damaged? But wouldn't there be oil around it if there was a leak? Any suggestions?

[R1000K3]

The vacuum for the brake booster has nothing to do with engine vaccum. There is a separate vacuum pump for the brakes. The oil filler cap also have no influence on engine vacuum since the engine vacuum is measured in the charge pipe.

The change in vacuum can depend in a slight leak somewhere in the charge pipe or the connections to it. But is could also depend in natural small variations caused by changes in idle RPM etc.

[dzenno]

What vacuum do you guys typically see on your vac/boost gauges at idle?

[ttbmer]

I normally see -20 or -22 but lately i keep seeing -17 -15 I might need to recalibrate the gauge