Coolant cap keeps breaking

[FiestaSTdude]

This is the second time that my coolant cap has come apart! Anyone else have this issue?

 

[SteveS]

In 2 and a half years, I have yet to unscrew that cap.

 

[FiestaSTdude]

Thankfully I happen to have a new reservoir that came with a cap. Never could get out the other cap

 

[M-Sport fan]

Mine is very very difficult to turn, in either direction, but it has never sheared off completely like that.

 

[NATYPE]

I had some cooling system issues with my non ST a few years ago that would cause it to generate such a vacuum within that resovoir that the plastic could crack, the cap could be incredibly stuck, or hell... maybe it even had enough force to start to pull the cap apart like that! Wacky. Wonder if you could be dealing with a similar-ish issue somewhere. It ended up being torn down / cleaned / who knows what really happened by the dealership under warranty.

 

[DEss]

This is the second time that my coolant cap has come apart! Anyone else have this issue?
View attachment 49281

I put a thin layer of grease on the gasket to prevent this