The alternator oil pipe on combo van leaking does feed the vacuum and the return pipe.
it is possibly a heater hose
Alternator oil pipe? There is no oil pipe connected to the alternator that I have ever seen. The alternator has sealed bearings and does not require any outside lubrication. Are you sure you are looking at the alternator? Is it possible you have a leak at the power steering pump and that is what you are looking at? I really have no answer for you, only more questions. Please clarify. Clay is absolutely right. The alternator has no outside oil connection. Find out what REALLY is leaking. A/C compressor? Power Steering?
When repairing a leaking pipe, you need a plastic tube that is not leaking and with a mouth a little larger than the pipe you are replacing. No specific kind of tubing would be preferable over another type.
If it is leaking when you use the shower, not shutting off completely, it will need to be replaced. If it is leaking at the wall, take it off and reseal the thread on the pipe with either pipe dope or Teflon tape and reinstall.
The exhaust pipe was leaking.
This is done by plumbers or depending on the Pipe engineers.
Seep
What is above your ceiling. Chances are it is a leaking pipe (probably a waste pipe-ick) or condensation from around your air ducts. Is this a house? Leaking on 1st level or a basement? Is it a "drop" ceiling?
Copper can rust
What is the question?
leaking
An overflow pipe on a (toilet cistern?) will leak if the rubber disc in the ballcock slide valve needs to be replaced.