Make up a solution of sodium carbonate (washing soda, not bicarbonate) and TSP (tri-sodium phosphate). I get the former at the grocery store (an old timey one) and the latter at Lowes.
This should have a good high pH, and be not quite saturated at room temp. Boil hard in this solution for about an hour, and if you've got a real tough one, a spoon or two of lye in there helps too. This is a non critical recipe. When making up a couple gallons of solution for my degreasing for plating I just put in a couple handfuls of this, and a handful of that...I sometimes add a spoon or two of lye, and/or borax. They all help get the oil off. Note this is for hydrocarbon oils, I don't have much experience with silicones, other than they are much harder to get off, usually needing a halogen type solvent at some point, and just more scrupulous work.
If it's something as insanely hard to clean out as a bellows pipe -- you should be lifting one end, then the other out of solution during this time to get flow through the tube or it will still be filthy in there. You can't use this on aluminum, though, which has it's own set of issues. At any rate, call this "step one".
Step two is rinsing, and I mean really rinsing, with flow. First with tap water, then distilled -- maybe even add a little denatured alcohol to the final rinse. Blow dry with compressed air, or otherwise remove the water between rinsings, don't let it just dry there leaving any dissolved contaminant behind, which kind of defeats the purpose.
For problem cases I bake parts in my powder coat oven for a couple of hours, particularly aluminum. It's just amazing how much cutting lube, oil, whatever can get beneath the surface of that stuff. A home oven at full heat will do this, and things you thought were clean -- get a visible coat of burnt oil or whatever on them, proving this out. Then you can mechanically clean (sandblast, sandpaper, degreased steel wool -- and it needs the boil treatment above to get that way) or whatever, then you can do the boil in oil solvent thing again.
Sometimes you need to repeat all these steps from the beginning, if you're trying to get a good adherent electroplate on the part. It's that picky, and I'd guess that vacuum systems are even more picky. A single fingerprint from a washed and dried hand will mess up either one -- you can see "fingerprint" on my mass spectrometer in the vacuum case, and in the plating case, it may as well be a process resist -- you get a nice picture of your print in metal, with the plate not sticking to the ridges in your print
The high pH stuff that you can use for most materials will eat and pit the aluminum, so you can't use that on it if that would be a problem, else, just keep an eye on it and fish it out before there's trouble from that. I usually use some solvent, or something else, or just allow some etching to occur. It's a great way to clean things if you don't worry about surface finish -- just eat some away that the dirt was sticking to, and the dirt comes off too. Either weak lye or HCl does aluminum all too fast -- less is more, here. I have also found that anodizing it seems to take care of any oil, and when it doesn't -- you can see that pretty well if you went in with it shiny - the contaminated parts will stay mirror, while the anodized parts of the piece get a faint haze.
A vapor phase degrease on Al is good, but more often than not, not quite good enough. Alternate with the oven treatment and see --if you get black or brown, it didn't get it done.
Hopefully I will get that anodizing thread going soon, as it's a useful technique for a lot of things, even vacuum (despite what some say). Done right, it's a great electrical insulator as well.
If done and then sealed up right, it's not a noticeable source of outgassing here -- but that takes a little finesse and following the rules (and no dye in vacuum!).
