1990 3.9 +8. My second water pump has failed in 38,000 miles. Has anyone got tips on replacing? I know the bolts can be a nightmare to remove from the block. Do I have to remove the radiator for access? Are there any improved designs available with a better life than the OEM?
Thanks, Chris
How do these failures express themselves..with leaking from the little holes underneath?
Those leak is an announcement that the bearing is about to go south on holiday and has decided not to take the engine with it. 
There are better made pumps from the 215 market in the USA, but they will not fit a 3.9 or later..only +8s from 1968 to 1990ish. So you are stuck with what you have. (I have a 3.9 pump in spares which I modified to fit my engine, but it is my just-in-case backup
along with some Sd1 pumps or else I would send it to you. .
However, despite all the UK the Manuals' warnings that these water pumps are not reparable, the US Buick 215 crowd has been doing so for years. In fact, any person in that metier can do so without the kit. https://www.rockauto.com/en/catalog/buick,1963,special,3.5l+215cid+v8,1319644,engine,oil+pump+repair+kit,5584 Be careful, I have seen to kits charged out as high as 300+ which is too much in any currency. Your woes may merely caused by poor workmanship. There are NO new 3.9 water pumps. They are all rebuilts from India. You will hopefully do better with a rebuild closer to home or by yourself. Frankly, I would buy two kits. The second kit normally makes the first kit behave..seriously. Weird but true.
You can ignore the other advice on removing the pump. It is the
crossbar that is the obstruction so please
don't touch the radiator. The amount of room you have varies with each Plus 8, but I (or those I have advised) have been able to manage it with most engine types.
3.5s, 3.9s, 4,0s and 4.6s. One can even remove the entire engine while leaving the gearbox, radiator and cowl in place!Here is the trick. Take out the bolts holding the water pump pulley on. That will give you the wiggle room you need and save you many long hours of unnecessary work or money. Figure 45 minutes for us amateurs.
The WATCHPOINT is to put back the pulley
loosely (as in around the neck of the pump but unbolted), BEFORE you re-install. If you forget that, you may have to start the whole business over with a new gasket OR talk to me again. (mona lisa smile) As for the gasket (a 3.9 one!!) lightly coat it with RTV/Hylomar/Silicone as with the little and long bolts.
Please report.
L.
https://www.gomog.com/headgaskets.html#Pump
Some things never change! 