I got the mirror off and while twisting it one way and another it suddenly moved and came apart, it seems the loose part should not normally move when the mirror turns, there is like a metal plate with tongues on which slot in and twist to attach to the plastic housing, this joint had for some reason worn although it should never move.
I have taken some pictures to show the mirror coming apart, I believe the best way to achieve this is to have the mirror in the open out position and then apply force as if trying to push it back in towards the car and it should suddenly release(if it doesn't break first).
Although I removed the mirror from the door first, I think this repair could be done without disturbing the door card.
Once the mirror was off I tapped the three 4mm holes in the metal part out to M5 and then used a 5.1mm drill to drill into the three slots in the plastic bit and out the bottom of the outer case, I then drilled 8.5mm into the bottom to allow the head of the M5 caphead screw to pass through and grip against the inner plastic.
Then put the mirror back on and twist a little to align the holes, before inserting the screws which shouldn't be overtightened. It may help to put a little point on the end to help them go into the metal part. This is where taking the mirror off makes it easier.
After this the mirror is now very rigid in the open position and operates as it should. In fact I am wondering whether to do the passenger side as this has a very slight wobble.
The finished repair is hardly noticeable as the screw heads are on the underside.
I have taken some pictures to show the mirror coming apart, I believe the best way to achieve this is to have the mirror in the open out position and then apply force as if trying to push it back in towards the car and it should suddenly release(if it doesn't break first).
Although I removed the mirror from the door first, I think this repair could be done without disturbing the door card.
Once the mirror was off I tapped the three 4mm holes in the metal part out to M5 and then used a 5.1mm drill to drill into the three slots in the plastic bit and out the bottom of the outer case, I then drilled 8.5mm into the bottom to allow the head of the M5 caphead screw to pass through and grip against the inner plastic.
Then put the mirror back on and twist a little to align the holes, before inserting the screws which shouldn't be overtightened. It may help to put a little point on the end to help them go into the metal part. This is where taking the mirror off makes it easier.
After this the mirror is now very rigid in the open position and operates as it should. In fact I am wondering whether to do the passenger side as this has a very slight wobble.
The finished repair is hardly noticeable as the screw heads are on the underside.