Wet vac pump question

[JFLEISC]

In my continuing effort to plug all the oil leaks in my Continental 0-300 I
have a final question about wet vacuum pumps. How much oil out the vent is too
much? This is a '61 C-172 with the factory standard oil recovery system off the
wet vac. About twice as much oil comes out the vacuum vent as out the engine
vent. Is that normal and if not what is the fix? Are there seals in the pump
that wear out or something? Any info would be appreciated.

Jim

[Rip]

Wet pumps have no seals, per se, and in fact get their lubricating oil
from the accessory pad they are driven from. On many engines this means
that the seal is removed from the drive pad. Internally, the pumps have
either steel (ARO), or heavy graphite (Pesco, Garwin) vanes that do
eventually wear out, but you would tend to see this wear indicated by
poor vacuum, rather than extra oil. The typical "output" of these pumps
is a lot of air with a fair amount of oil entrained, almost like the
spray from an aerosol can. The engine breather vent should have almost
no oil at all, and at extremely low pressure (inches of water, rather
than PSI). Unfortunately, most air/oil separators don't do a very good
job. I've tried 4 or 5 different units, and only the Airwolf did what it
was advertised to do.

JFLEISC wrote:
> In my continuing effort to plug all the oil leaks in my Continental 0-300 I
> have a final question about wet vacuum pumps. How much oil out the vent is too
> much? This is a '61 C-172 with the factory standard oil recovery system off the
> wet vac. About twice as much oil comes out the vacuum vent as out the engine
> vent. Is that normal and if not what is the fix? Are there seals in the pump
> that wear out or something? Any info would be appreciated.
>
> Jim
>

[JFLEISC]

>The typical "output" of these pumps
>is a lot of air with a fair amount of oil entrained, almost like the
>spray from an aerosol can.

> I've tried 4 or 5 different units, and only the Airwolf did what it
>was advertised to do.
>

I was afraid of that. Cheaper to go with a dry pump, I think.

Jim

[Newps]

"JFLEISC" > wrote in message
...
> >The typical "output" of these pumps
> >is a lot of air with a fair amount of oil entrained, almost like the
> >spray from an aerosol can.
>
> > I've tried 4 or 5 different units, and only the Airwolf did what it
> >was advertised to do.
> >
>
> I was afraid of that. Cheaper to go with a dry pump, I think.

Then you have no experience with a wet pump. Dry pumps are an absolute
joke. Owners rave about getting 500 hours out of one. I have a Garwin wet
pump on my 182. I give it exactly zero thought. No oil on the belly from
the pump either.

[Javier Henderson]

(JFLEISC) writes:

> >The typical "output" of these pumps
> >is a lot of air with a fair amount of oil entrained, almost like the
> >spray from an aerosol can.
>
> > I've tried 4 or 5 different units, and only the Airwolf did what it
> >was advertised to do.
> >
>
> I was afraid of that. Cheaper to go with a dry pump, I think.

I think it's more of a lottery. Wet pumps, from what I read, will
outlast your engine, whereas dry pumps can last anywhere from .1 to
many hundreds of hours. But let's say they last 500 hours on the
average, that's four pumps over a 2000 hour TBO engine, reducing the
financial advantage of the dry vs. wet pumps.

-jav

[Rip]

Agreed. I won't fly hard IFR with a dry pump, and I laugh each time I
throw one of those Parker Hannafin "mandatory" notices in the trash,
unopened. The last wet pump I had overhauled had over 3000 hours on it,
and the overhaul facility changed the bearings, just so they could say
they had done something.


Javier Henderson wrote:
> (JFLEISC) writes:
>
>
>>>The typical "output" of these pumps
>>>is a lot of air with a fair amount of oil entrained, almost like the
>>>spray from an aerosol can.
>>
>>>I've tried 4 or 5 different units, and only the Airwolf did what it
>>>was advertised to do.
>>>
>>
>>I was afraid of that. Cheaper to go with a dry pump, I think.
>
>
> I think it's more of a lottery. Wet pumps, from what I read, will
> outlast your engine, whereas dry pumps can last anywhere from .1 to
> many hundreds of hours. But let's say they last 500 hours on the
> average, that's four pumps over a 2000 hour TBO engine, reducing the
> financial advantage of the dry vs. wet pumps.
>
> -jav

[JFLEISC]

>Then you have no experience with a wet pump.

That's right, I don't. What I'm interested in right now is cutting down the oil
usage. It's not likely this plane will be used for IFR except possibly as a
trainer.

Jim

[G.R. Patterson III]

JFLEISC wrote:
>
> That's right, I don't. What I'm interested in right now is cutting down the oil
> usage. It's not likely this plane will be used for IFR except possibly as a
> trainer.

In that case, make sure you keep the old vacuum pump when you replace the pump with a
dry unit. You ought to be able to get a fair price for it.

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.

[Newps]

"JFLEISC" > wrote in message
...
> >Then you have no experience with a wet pump.
>
> That's right, I don't. What I'm interested in right now is cutting down
the oil
> usage. It's not likely this plane will be used for IFR except possibly as
a
> trainer.

Any wet pump that uses enough oil to be noticeable is in need of overhaul.

[JFLEISC]

>Any wet pump that uses enough oil to be noticeable is in need of overhaul.

This is what I was wondering. I don't mind getting an overhauled pump if that
will stop it's oil usage, but the feedback on this thread leads me to believe
that many in this group think that 'noticable' quantities of oil out the wet
vac vent tube is normal. Do I have the wrong impression here (I hope)?

Jim

[Matt Whiting]

Rip wrote:

> Agreed. I won't fly hard IFR with a dry pump, and I laugh each time I
> throw one of those Parker Hannafin "mandatory" notices in the trash,
> unopened. The last wet pump I had overhauled had over 3000 hours on it,
> and the overhaul facility changed the bearings, just so they could say
> they had done something.

I agree. Dry pumps should be outlawed! :-)


Matt

[Matt Whiting]

JFLEISC wrote:

>>Any wet pump that uses enough oil to be noticeable is in need of overhaul.
>
>
> This is what I was wondering. I don't mind getting an overhauled pump if that
> will stop it's oil usage, but the feedback on this thread leads me to believe
> that many in this group think that 'noticable' quantities of oil out the wet
> vac vent tube is normal. Do I have the wrong impression here (I hope)?
>
> Jim

Yes, you have the wrong impression. After owning a Skylane for several
years, we had no issue with oil consumption due to the vacuum pump, but
did get enough oil on the belly to require an annual clean-up. However,
it takes very little oil to completely soil the bottom of an airplane.
Probably less than half a cup.


Matt