Chrome Windscreen Rubber Softening

List: I am reinstalling the chrome, front and rear, windscreen surrounds The rubber on the front is original, the rear perhaps 1990. Is there anything to be done, particularly on the front, to soften the rubber for the installation process?

Thank You


Way back when I worked at a full service station.

As a part of a “grease job” we used a goop known as rubber lube. if none available, we used brake fluid…

Might take a page from the tire guys. Rich soap suds to ease the bead over the wheel. In your case, the finisher into the rubber around the glass…

I might almost, but not quite, suggest. petroleum jelly aka Vaseline for the job…

Or miladies hand cream???


there are stories about softening old rubber with silicone, washing powder or sunscreen … I don’t believe them. Once the molecular structure of the rubber is destroyed you won’t get it rebuilt by any additive; you may fill in cracks or make it feel slippery, but it won’t help.

As long as your screens are out anyhow and the gaskets are still available at a reasonable rate I’d replace them. If you don’t want to, but dislike wet feet and rusty floor pans, you might use the old rubber, but reseal it with some kind of sealant that was used on a car of mine some 15 years ago and still works fine.

It was a 3M product, it came in a 400 ml can to be mounted in the type of silicone pumps, it was black and supposed not to harden, but to remain elastic. It was inserted over the nozzle between the glass and the rubber and betwen the rubber and the metal lip.

Good luck


75 XJ6L 4.2 auto (UK spec)

Good: they don’t work.

Old rubber is…old rubber.

YUP, just means of getting the chrome finisher in place.

A weirds idea ! Not recommended kinda like the disclaimers used by the You Tube mechanics.

Transmission or rack sealers, ala Lucas products. soften the rubber seals and ease or stop the leak…


Honestly, maybe you should think about renewing that front screen rubber. They are not expensive and old ones can start to leak. The cost of the exercise is mostly in the removal and refitting of front screen anyway and you’ve already got that costed in.

It would be a pain to get it all back together then find now or in a year or so that it needed replacing. Rubber hardens over the years and really can’t be effectively resoftened.

Buy the OE quality ones if you do, they are streets ahead of the repro ones and not much price difference.

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As everyone said - go for a new rubber seal as long as they are available.

When it comes to using sealants - I’ve found out the 3M product I was talking about: it is 3M 08509 and it is still available after probably +20 ys



75 XJ6L 4.2 auto (UK spec)