Hartal Roof Vent Replace

[Dopey]

Hi
I have an ancient caravan with I believe a Hartal roof vent which has a broken lock bar allowing the spring to escape. I've researched on the net - I assume it is easy to replace, but I'm not clear re adhesive. should I use double sided adhesive 19mm mastic tape? supplier suggesting idl / hodgson non setting mastic sealant?
greatly appreciate confirmation / advise of which I should use
thanks
Dopey

 

[Damian]

After removing the old unit and thoroughly cleaning off all old mastic use IDL99 as per your suppliers advice.