I didn't find a definitive answer as to which water pump bolts need sealant that I felt 100% confident in given the discrepancy of answers, but I am now 99.9% confident in fierosound's answer that only hole #4 needs sealant. I remembered a tool I have and rarely use: an inspection camera. It could fit into all but the small bolt holes. What follows is a series of pictures that I took. I went through the rotation twice. There are some differences because between rounds I sprayed brake cleaner in and tried blowing out the holes. What I found was that Hole #4 DEFINATELY needs thread sealant. I am not totally sure about Hole #5. It looks like it doesn't. Holes #5 and #7 flank the incoming water. Necessary or not, it wouldn't be a bad idea to thread seal these holes too. As for all the others, I don't think any of them need sealant as they are each blind holes. In summary...and this is being on the cautious side...only holes #4, #5, and #7 should need sealant. Hole #4 looks to be the only hole going into a water jacket. Hole #12 was dry in the first picture, but wet in the second. Remember, I spayed in brake clean.

The following pictures are first the famous bolt tightening sequence picture from which I named the holes. Hole # Take # 1 and 2 follow for each hole. You can compare each and draw your own conclusions.



























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Stanton
'88 Formula, red on gray

[This message has been edited by oneinch (edited 01-15-2021).]

That's a very nice study with the boroscope! On my 88 2.8L I just sealed hole #4, no leaks.

Diligent work. Thanks for sharing!