A vacuum pump caused the timing chain to break?
The author wrote “vacuum pump” but later wrote “water pump”. I expect “vacuum pump” was a typo. I don’t know of any “vacuum pumps” driven by timing chains.
I always wanted a mini so I did some reading ... the problem seems to be a hydraulic tensioner that leaks (since updated) and the chain is a single wide that wears out very quickly ... I’ve had other cars with chains go 200,000+ miles without reaching the limits of the tensioner... mini’s are wearing out chains at 25-60,000 miles... this is a defective chain , chains do not stretch... what is termed “stretch” is actually wear at the joints.
This is actually good news for me ... I want an early mini with the “death rattle” from a bad chain .. and I want it dirt cheap... I’ll change it out while I have the head off for porting.