Article by: Paul Axford
Applies to: All e32 and e34 models (this article was written with a 730i).
Inspection of the trunk gasket after a heavy rain showed that water was getting underneath the rubber.
No doubt this would be a source of eventual rust.
This was occurring mainly because the rubber had shrunk in the top corners such that the seal at the base of the gasket to the body was not being maintained (see pic 1.)
The opening was large enough to capture any water running off the back window. The water then travels under the gasket and all the way down into the top area of the tail light lenses.
It became immediately clear that the best approach to this problem was to remove the gasket entirely for best access. It is necessary to remove the taillight assemblies first.
This is easy – remove (5) 8mm nuts each and they just pop out.
Next remove the plastic protective edge along the top of the trunk opening.
You just push the center pins inside each of the four retainers right through. You will need to recover the pins however as they will have scattered everywhere.
After I pulled the gasket out I cleaned the groove with soapy water, a rag, and a small brush.
The rubber gasket was wiped down with turpentine (white spirits) to remove remains of the original sealant. I also cleaned the taillight lenses somewhat just to get the mud out.
Be careful not to get water inside the unit or electrical connector.
Re-assembly was done with a bead of silicone RTV* around the outer bottom edge of the trunk groove along the front and side, as far as the flat area goes.
The idea was to provide a permanent seal between the gasket and body at the gasket’s outer edge.
Afterwards I filled the gaps in the corners (see pic 3) and added an additional small bead along the gasket front edge (under the rear window.)
Before re-installation the taillight gaskets were coated with a very thin touch of Castrol Rubber Grease and the electrical connector with silicone dielectric grease.
The 8mm nuts are tightened evenly and carefully until you feel them “seat.”