Harmonic Balancer bolt falls out (I think)

[catchmup]

My 1989 4wd v6 4Runner has had this problem twice. The pully (I think harmonic balancer) that is outside the timing chain has a bolt that holds the pully in place, this pully runs all the belts. (obviously I'm not a mechanic) Anyway the bolt came out twice in the last year. Putting it back in is a major pain on this engine model. Just wondering if I should take her to a dealer or keep doing this myself. This is my weekend car and am the original owner. The vehicle only has 123000 miles and I'd like to keep driving it. But since I don't do a lot of toying around with cars just wondering if she's worth putting money into. Let me know if anyone has any suggestions on what could be wrong or how much a dealer would charge. Thanks Scott

[catchmup]

I got the bolt back in here's how I did it.

Removed the fan shroud, removed the fan (this is hard with the radiator in the way) once out I was able to loosen the alternator belt and the power steering belt. Then I was able to get the bolt back in. My question now is even though I'm holding the starter pulley and tightening the bolt is it tight enough. Since this is the second time this has happened I don't think it will be. Any thoughts and back to the original question, is this a dealer issue and could something be bent just enough to keep spinning the bolt out?????

[catchmup]

Obviously, I know nothing about what i'm talking about. Apparently this is the crankshaft bolt that holds the pulley in place. Put everything back together with a little bolt lock and it came right out. I give up.

1989 Toyota 4runner 123k miles for sale!