Hi everyone,
Thanks for your answers
jwc66k,
Digging in my own reserve of bolts, I was able to find the correct one, so no worries
You are right : time is the enemy. This car have been stored in a garage in southern California from 2010 to 2020. Then sold and shipped to France but didn't move much up to dec, 2021 when I bought it. I had the relevant problems : change of seals, gaskets, hoses...
Bossbill,
There isn't broken bolt, just a missing one which explains the leakage and the sediment deposit
Indeed there is corrosion inside
I was thinking of using a radiator cleaner from Bardahl to clean the whole cooling system ; what do you think ?
Have a good day,
Didier