[cj romeo]

One would have thought it was M6 being European.

Is the bolt a bit tight in the thread - if so tap it out to M6?

1/4 inch is a bit bigger than M6 so it might just be a fine pitch.

 

[cj romeo]

Tap the ******* then.

 

[cj romeo]

It's another of the crappy Delphi components that these cars have then, that's a favourite fastener size of theirs.