When I came to switching the ECT sensor on my 98 GEMS, it turns out that my PO stripped the seat of the sensor and glued it into place with something hard/ yellow. I'm guessing it was an epoxy glue. The question now is what's my best option to reseat it. Is it helicoilable? Or should I go the way of the PO and glue it into place? If so, what's the best glue/ to use?

If it were mine, I'd helicoil it. It's not something you want to work loose and dump all your coolant without you realising it.

Ok, I've got an M12 x 1.5mm helicoil kit on order. Do you think i'm going to need to take the whole inlet manifold off etc to do this, or does someone have a clever idea for collecting the swarf and tang without it dropping into the water gallery?
I should probably be able to get the tang off with a pair of long nose tweezers, since this is M12, and recover most of the swarth using a bit of grease to cut with the tap. Where would these bits of swarth end up - bottom of the radiator?
Still, if i need to strip it down, it could be worse, and I'll test my fuel injectors at the same time

Plenty of grease on the tap usually collects the swarf in a satisfactory manner. I'm surprised Helicoil don't offer form taps for this sort of job. No swarf. Dunno about collecting the tang. Allegedly magnetising the end of the tool helps.

Potential tang collection issues is why I use Wurth Timeserts rather than helicoils as these are solid bushes with both internal and outside threads expanded into place by the insertion tool. More expensive and theoretically capable of coming loose at high temperatures in aluminium due to differential expansion between the steel bush and alloy. A Helicoil being basically a spring is said to follow the expansion. I've never had any issues and think the analysis is over simple.

Clive

I have no experience with the Timesert, but as the ECT is in contact with the coolant, it should never get very hot (usually max temp around 95C), so thermal expansion is probably not that big a deal in this location.

Thanks for the extra option Clive. The time serts sound good, but I guess for the price I would then just buy a second hand inlet manifold, which is always an option as they're only 30-40 pounds. I think I'll just strip mine down and helicoil it, I was being lazy :o)

Good news !! With apologies to my PO, this may be more of a salutary tale of Lucas quality. I'd spared you this bit, but the replacement Lucas ECT sensor (made in China) didn't clip up to the engine harness correctly (i think the blades may have been 1 or 2 mm too long, so the assembly couldn't quite clip shut). I drained the coolant today, ready to remove the Lucas replacement from the housing, or tried... turned out the plastic connector/ 19mm hex was just turning on top of the brass sensor which was nice and snug in the inlet manifold. I obviously misinterpreted the slipping of plastic on brass to be brass on aluminium.
Now, maybe i tightened it a bit too hard, but since the manufacturer didn't care too much about making the connector fit correctly I reckon it was just poor quality period. Reading up on the Lucas company history they seem to have simply been sucked up into the ZF business empire and the name is licensed out. Maybe the Lucas box even guarantees it's a chinese knock off, as it looks like only lighting was licensed - or maybe I'm just the last person here to have worked this out :o)

My experience of buying "Lucas" stuff recently is that its utter garbage. As an example i've been thru four crank sensors on my GEMS. The original chinese cheapy one that the PO fitted, one in a Lucas box and one in a Facet (i think) box, all looked identical. Clearly from the same chinese factory and all failed within a few months in the same way, losing signal when hot.

In the end i found a new old stock Rover part that came in an LDV box, and it looked quite different to the three chinesium ones, as well as actually working correctly.

I'm fairly sure at this point its just a box/brand thats rebadging chinese junk.

Yep, I won't touch Lucas and have studiously avoided them for years.