It just pulls right out, if you grab the center part and pull it out....like the vacuum does....it just pops right out....it won't come off the rack with out removing the pin....also the diaghram is double layered...so the tares may not go all the way through.....did you confirm the clear plastic line that runs from the housing to the manifold is intact and not cracked?

Also check your coolant for oil....my friends car was doing this and eventually the head gasket blew...the coolant became oil...

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