On May 11, 8:53*am, wrote:
I purchased a used Robinair 15102-A vac pump last winter (much better
price off season). *Now I am ready to use it. *I added oil (did not
replace the old oil since I was doing a test evacuation) and hooked
the vac pump up to the vehicle's A/C system. *I was able to pull 26 or
27 in of Hg of vacum. *As I understand it I will need to pull 29 in of
Hg to properly evacuate the A/C system (after repair).

Will changing the oil have an effect on the pump's performance (pull a
stronger vacuum)? * I searched for a manual or an exploded view of the
pump with no success. * What other sort of maintanence might I need to
do to the pump? *Other than hooking the pump up and letting it run,
are there any other proceedures that I should / need to follow?
Suggestions / links to info very much appreciated.

Oil will pick up all sorts of volatiles, I strongly recommend dumping
the old stuff and putting in fresh. Keeping the intake and outlet
sealed between sessions will help, too. You need vacuum pump oil,
too, not just car oil. Just thought I'd mention that, you never know
what some people will do...

Manufacturers sometimes will have rebuild kits, I know Welch pumps
do. Used vac pumps can be a crap-shoot, you never know what kind of
service the thing's been in, once a month, once a week, 24/7, you just
never know. If it's been in the usual repair garage, nobody's changed
the oil since it's been bought new.

Don't be too quick to blame the pump, a car A/C system has lots of
leak potential, until you've replaced all the seals, you won't know
what you've got. Attach the vac gauge directly to the pump and test
it that way. Refrigerant sniffers have come waaay down, that would be
my first choice for tracing leaks. Even HF has one, not that that's
what I have.

Stan