Thanks for all the advice. I've been doing some research, and Bars Leaks seems to have been a mainstay for a lot of people for a long time. Some others that have also gotten good reviews are Thermaweld, Thermaseal, Steel Seal, K and W Block Seal and K-seal, none of which have particles that could conceivably clog passages. Some people have said that the active ingredient in many of these is sodium silicate, which you can buy for peanuts from any chemical company.

I'm not sure a block sealer will work if my leak is from the intake manifold gasket, though, as the temperature there may not be high enough to cause the chemical reaction these product need. The Thermaseal people says it will seal intake manifold leaks, though

The only thing i'm still worried about is whether these products will damage the mechanism in the AC servo, as I'm not really sure how that works, and it seems to have a lot of moving parts that could get sealed along with the leak????

So, any additional advice would be greatly appreciated.