Why do I keep losing vaccum caps?

[Anonymous]

I have a unused vaccum port on my manifold, it is capped of with a little vaccum cap that keeps coming off. tis will be the third time now that I have had to put a new one on I'm not sure when they are coming off? or why? but it seems to me like this should not be a problem.

 

[jahearne]

backfiring?

 

[fordconvert]

Backfire is how I used to loose them.

 

[Anonymous]

not unless it is backfiring without me noticing

 

[pedal2themetal45]

How high is your idle, when you shut it off does it turn backwards a little. that could push it off.
tim

 

[The Plankster Prankster]

thats what it is.
to save your caps, just put a hose clamp holding it on.