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Topic-icon Wet Vacuum Pump

2 years 1 month ago #957


New to the forum but found nothing in the search function, so here goes. I have an Apache/Geronimo with 2 wet vac pumps. The left side stays relatively dry but the right flap gets dripping wet after 10 or so hours. I did a run this morning (3-5 minutes) with a rag covering the vacuum pump output hose in lieu of it going into the (tiny) separator. This yielded a pretty nasty rag. My conclusion is that the wet pump is putting out excessive amounts of oil. I'm sure there are also other sources but this seems to be a large & confirmed one.

I understand that there is a seal around the input shaft to the pump. Is this a possible solution or is the oil output indicative of internal wear and will not be affected by the shaft seal? I'd hate to replace the pump if it is not needed but will in a heartbeat if the pump is spent.

Steve Rochna

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2 years 5 days ago #973

First off, I am a big fan of wet vacuum pumps. They just wear out; they don't destruct like dry pumps. That said, there have been many upgrades and improvements in dry pump technology during the last 10 years.
According to information I have a healthy wet pump should exhaust 20 to 50 cc of oil per hour. This converts to 0.67 to 1.69 fluid ounces. Although that doesn't sound like much when one fluid ounces of 50 weight engine oil is heated to 180 degrees it will make a big mess if there's a leak.
All wet pump systems are equipped with a oil/air separator which is designed to separate the and re-capture the oil in the pump exhaust and return it to the engine.
It's not uncommon for air oil separators, especially small original equipment ones on older airplanes to get clogged up with carbon and crud. They should be removed and thoroughly cleaned at regular intervals.
I've also seen restrictions in the oil return lines from the separator to the engine.
Before I removed a pump I would check to make sure the air/oil sep is clean and open so oil can return freely to the engine.
There is a seal around the drive gear (it's called a Garlock seal) that, if leaking will allow excess oil to be pulled into the pump. The part number of the seal on you Lycoming engine is part number STD-208. These cost under $7.
I would clean the air oil seps and the return line first.
Then I would check the Garlock seal.
If they're good it's time to send you pump for overhaul, or exchange your pump. Exchange prices are between $500 and $600 depending on whether it's a Pesco or a Garwin pump.
Let me know what you find,

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2 years 5 days ago #974

I also am a wet pump fan, have an overhauled unit ready to go. Job currently held up awaiting the garlic which is back ordered from spruce.

Thanks for the info-I'll be cleaning the breather and tubes at the same time as I don't want to pull the cowling any more than required.
Steve Rochna

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1 year 11 months ago #981

Cleaned breather tubes and breather, replaced Garlock seal and R&R'd pump w/rebuilt unit from Spruce. No oil spewing after about 6 hours on it. Problem solved.

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