As this is a continuing theme on the forum, I thought a bit of scientific examination was called for.
I bought a genuine (Rimmer bros) expansion cap and another eBay bargain, which was half the price of Rimmers.
Here they are together.
And the insides.
NOW THEN:- Which is genuine and does it make any difference?
I tested both with my pressure tester setup.
Results:- 1 held around
14-
15
psi,
1 held around
6
psi.