I was wondering that as well as I've heard about this a few times. If anyone knows, I would really appreciate knowing:

- What causes the vacuum pump to fail?
- I've heard the vacuum pump rebuild kits don't always work right. Why is that?
- Are there warning signs before the vacuum pump fails? Is it enough to drive home and fix later or will it just die and spit it's guts into the engine?
- Can inspecting the existing vacuum pump help to determine it's condition and longevity?

Dkr.