I checked with our resident Boeing rep and he confirmed that the centre tank pumps on the B737-200 are located in an "igloo" in the respective main tank. The reason for the AD is the fear of propogation of fumes in the centre tank due to prolonged running of the centre tank pumps on the ground in high temperature conditions with little or no lubrication.
I do not know why anyone would want the centre tank pumps on for a prolonged period on the ground anyway but that is just my opinion and you know what they say about opinions, they are like assholes, everyone has one :-))
Cheers