From Moss Motoring 1984
Prepared by Peter Cosmides, Manager, Moss-SYE Division
(Ed. Note: This article relates specifically to MGBs, using Moss seals #282-380 and 282-390. Other cars with wind-up windows would probably use a similar procedure. Austin Healeys, for example, use the exact same seal.)
The design of the door is, unfortunately, such that it is necessary to remove the side windows and vent windows in order to replace these door seals. However, the effort is worth making because bad seals allow water to get down into the door, which leads eventually to the bottom of the door rusting out. The procedure for removing the window glass is detailed in the Shop Manual but, briefly, it involves removing the door interior trim panel and top rail, then removing the seven bolts which secure the window regulator mechanism to the door. The vent window should then be removed in order to allow the door glass to be slid off the regulator top rail by angling up through the top of the door.
The old seal is removed by drilling out the rivets or removing the clips which secure it to the door. Be very careful doing this, as if you allow the drill to go too far, it will appear through the outer door skin! You can now pop-rivet the new door seal in place, or in the case of the MGB GT, simply replace the clips. Before starting to reassemble the door, use this opportunity of an “empty” door to wire brush any rust inside the door and paint with rust-proofing paint You can also lubricate the door-opening mechanism which the moisture has stiffened up and which causes those plastic handles to keep breaking!
Before you commence the re-installation of the door glass, it is a good idea to protect the new seal with several layers of masking tape. You have to bring the regulator top rail up past the seal to reattach the door glass, and the metal can easily damage the new seal. Care must be used as you slide the regulator and glass back into the door, because the seal tends to get in the way. Fit new seals under the vent windows (Moss #282-780 & 282-790 for all MGB roadsters or two #324-305 for all MGB GTs), and new brush seals to the door top rails (Moss #682-830), and your finished doors will be rain and draught proof. (Ed. Note: MGB brush seals staple to the door top rail. Other cars have them clipped to the inside top of the door itself, so if s easiest to replace them while the window is out.)