Originally Posted By: LS2JSTS
That nipple and the rubber gasket around it are what keep the oil in the canister at shut down and in effect act as the ADBV. I think the smaller of these nipples allow the oil to seap back into the sump. I have noticed differences in start up noise between filters in my 2.2.
As an experiment, I once placed a new filter into the empty filter bore just to see how tight the nipple was down there in its little cavity. It sure seemed reasonably tight. I suppose its possible that different rates of expansion and contraction, particularly on a cold engine, might allow some oil to get past the nipple overnight.
If I recall, there is a TSB that addresses startup noise regarding use of various filters. It advises the technician to check for evidence of missing, damaged or misaligned O-rings, and calls for lubing the O-ring on the replacement filter with oil before installing it. To me, the gist of the TSB was that the O-ring could be damaged if its too tight, thus damaging or bending the bottom of the filter enough to allow the oil to drain out. So is the issue too-loose, or too-tight? I'm not sure.
I get the rattle noise once in a great while, perhaps a few times a year. I always thought it was piston slap. I've never had a car with piston slap before, so its hard for me to say for sure. I'm at 104,000 miles on my Ecotec.
