How compatible is an 83 fb 12a water pump with an s5 NA? I noticed a leak on my Tstat neck which turned out to be due to a twisted off 10mm bolt on the neck base. Long story short while drilling out and retapping the broken thread hole I over torqued the new bolt and made a hair line crack between the top left 10mm and thermo sensor... It leaks just from squeezing the hose now.

Can I just put the s5 pump on the s2 housing? Or will I have to use the 12a complete assembly? or will it not work at all and I need a new s5 unit?

Looks like there is an extra bolt on the s5 housing.

 

why not yank the thing off and try and see if it fits. if not, bad luck. if yes, good job. this thread isnt necessary.

 

the s4 and 12a and s5 water pumps must go on the specific housing, s5 water pump has 1 extra bolt hole
and s4 and 12a water pumps are different from each other where the alt bracket bolt/stud fits

if you swap the entire water pump housing it will fit onto s4 if you bolt it up and ignore the extra hole at the gasket line and fill with silicon

for s5,, the same,, but you also have to grind the back of the water pump housing slightly at one spot as it will foul the s5 timing cover
( self explanitory when you fit them together )