Readers who encounter this problem with their vehicles may find my experiences in this area helpful, as I have finally cured the problem on the sloping rear window of my 1938 Morris 12.
Getting at the window is fairly straightforward if one begins by removing the screws which secure the combined assembly of rear seat plus back shelf behind to the rear window frame; these are accessed through the boot, and are quite high up. Next all the headlining needs to come out around the window, the material above the window can be tucked out of the way behind the rearmost hoop across the ceiling.
In my case the window frame had rotted right through on the bottom right hand side so complete replacement was indicated. To get the frame out I had to remove the curved metal straps which go around from the frame to the rear door jambs on either side and provide securing points for the headlining, followed by removing the carpet tacks which hold the frame to the bodywork around the windows, having already removed the rear window and what was left of the original rubber surround.
After some experimentation I realised the importance of following the original construction of the frame exactly, especially getting a snug fit of the new frame to the bodywork. The window glass and its surround are held in place by screws from the inner boards top and bottom being screwed tightly to the centre part of the frame in ordinary softwood rather than ash. The result was that the screws in the bottom member could not be tightened enough to give the necessary pressure, and I had to use bolts instead. Even this did not cure the leaks on both sides, and the window and surround were obviously loose, even if only slightly due presumably to the replacement rubber surround being metric rather than imperial. So I made plastic spacers and secured these to the top and bottom inner boards where they would press against the original right hand side where the trouble started. I assumed that the reason for continuing failure here was that the metal, which had become superficially rusty in that area was too rough to give a good seal, so I applied a thin layer of putty around the outside face of the rubber surround, reassembled and hey presto! The leak on the right hand side was cured but there was a little leakage on the left. So I carefully lifted the lip of the surround on the outside and, working with both hands simultaneously pressed home small amounts of putty all around the window until I could see that it had no sign of any point where water could possibly leak in. Success at last! No sign of any leakage was detected in about three hours of continuous light rain later that day.
I did enquire about the glass which had a Triplex kitemark being up to current safety standards and the man of the local Triplex garage assured me that 1938 was the first year that Triplex made auto glass up to modern safety standards so my window was OK.
Duncan Mac Duffie
Bibliography and Photographic credits
The Journal of the Morris Register, Summer 2000, Vol.16 No.6