Can I use Threadlock on a slide pin with a stripped thread, or has it got to have a Helicoil fitted?

I take it by stripped you mean it screws in part way then just turns? To be honest I'm not a fan of helicoils anyway, they never last long and always find a way of undoing themselves even with 577 or 222 loctite on. Depending on how badly it is stripped (if it starts to tighten but loosens off again) then you could probably get away with loctiting it in place.

Alternatively just buy a new set of guide pins for a tenner or so.

Thanks for the reply, it’s an old car, so I’ve decided to Araldite the pin in place. The car will probably be scrapped before I fit brake pads again

It's no wonder there are so many preventable accidents each year, a bodge on a brake caliper though, really? 

If you are talking about the guide pins with the 7mm hex in the end or indeed the sliding type, if the pin has stripped these are available quite cheap from a motor factors. If it is the knuckle side or carrier then you can fit a 'repair' insert which is considered a permanent fix - I have done a few of these now and they work well. 

 

A pair of guide pins is less than 15 sheets from a dealer.  Never, ever, take even the slightest shortcut with brakes or tyres.