My Vanagon's rubber windshield gasket was fine, but the plastic insert was all sun-rotted and impossible to reuse. EXIT

The rubber windshield gasket leaked pretty bad, so I decided to expand it a little. Some say the expander is purely cosmetic and has no effect on sealing from leakage. I don't know if these people also replaced the windshield.

UPDATE: 3 years later not one windshield leak ever, so this has proven to be a successful solution.

Here is a cross-section of the original plastic strip that spread out the gasket to supposedly prevent leakage.

I believe later models have a stainless steel strip covering the plastic, so they may be in better condition.

I bought a length of 7/32 OD fuel injector tube at the hardware store. This shows the size of the profile compared to the original.

Choose a warm day to do the job, but not too hot since the vaseline is absorbed into the rubber too fast in hot weather.

Inserting the tube in the gasket slot is difficult. Lubricate both the slot and the tube with vaseline copiously before you start. It will make a mess but is easily cleaned up afterwards. Excess vaseline will be absorbed into the rubber.

Use a blunt tool to insert under the edge of the rubber gasket. I used a closed hemostat and it worked well. Hold the tool down obliquely as you move it and press hard to force the tube in the slot. You will need to alternate sides in some places, but others go in easily for long stretches.

This picture shows the end result, which actually looks a lot better than the old discolored plastic. You can see where the original strip covered the rubber, and how the tube is visible through the slot.