Have a 1989 Syncro 2.1 wbx
Had a leak at the coolant level switch on the expansion tank.Removed it and found a hairline crack underneath the o-ring (o-ring was kaput as well)
Ordered a new switch with supplied o-ring.
Have fitted the new switch and coolant is still leaking around the area that the switch screws in .
Would silicone solve the problem
Regards
Philippe