Thermostat Housing Plug

Bought these to replace the plastic ones. Now the new rad has taken the blank plug but the thermostat housing will not accept either of them (the thread on the stat' is clean and damage free)

Does anyone know if LR used thermostat housing's with different thread size's?, as numerous threads on here say the standard size is 1/2" BSP.

I fiited those plugs to mine-seem to remember one was reluctant,but got em in eventually.
Check the male thread on the bung and file off any burrs

Plug's thread had been de-burred. Finally got it to fit by scraping the stat's thread with a pin ... there was a minute piece of plastic from the old plug that I'd missed still in there preventing the threads interlocking!

Lesson learnt, double check for clean surfaces when removing old parts

I think the ally changes shape slightly anorl with only a placcy plug in there to try and stop it with all the hot and cold excursions-glad ur sorted anyway-found I had to have mine out again to clear the bleed nipples on the new plugs