My XJ had a heater core leak 5 or more years ago. I could smell the sweet smell in the car.
I put this stuff in
https://www.supercheapauto.com.au/p/...E&gclsrc=aw.ds
And never looked back. Fixed the weep/pin hole and never affected anything else.
Worth a try at least.
Its not like that old crap that bungs everything up. These are like tiny gold flakes that keep your coolant clean, but get into cracks, pin holes and weeps.
Anyway, saved me pulling my dash apart.
cheers,