i've only had this happen on cars with PCV valves. our cars do not have a valve, just a vent. is your a/c running while you do this? you also might want to consider changing your timing chain tensioner i hear a lot of rattle. blowby would not cause this, because the motor is stopped. windage is only created while the motor is turning. a puff of air that big would be pretty obvious and would shoot a nice puff of smoke from the breather. if there were that much pressure built up in the crank case, your dipstick would fly out.
Last edited by ff_drift_lol; 09-21-2010 at 04:24 PM.