that sounds like making hard nylon fuel line repair of modern cars, The way I do it is to heat the line in boiling water and immediately push on the barb. You can also form the line into shape if you are feeling crafty.

I have done this a few times on fuel injection fuel hoses. Same principle.

You can also use a heat gun, but I think water is more safe as it wont melt the plastic

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)