So I got a new O-ring as PM (DAC 6949) from JLR classic (#8 in diagram below).




To replace this one:


I note that the old one has a square cross section and the new one has a round cross section. Thoughts if that makes any difference?
Quentin

 

It's square because it's old and hard. New ones are round.

 

I did wonder if that was the reason!
It just does look v. Square, rather than round but compressed with age. However, sounds reasonable as God knows when it was last changed.

 

Probably original to the car.