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Could I Have The Wrong Turbocharger Oil Scavenge Pump???

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HomeBuilt101

Well-Known Member
Joined
Oct 20, 2015
Messages
384
Location
Aguila AZ
I have just reinstalled a rebuilt, normal turning direction IO-540 with a single automotive turbocharger mounted below the engine. The first five engine runs at 1200 RPM and the two full engine power engine runs were normal. The eighth full power engine run was normal with no oil drips nor exhaust smoke after shut down. A few minutes after the last engine run there was a VERY minor amount of oil smoke from the exhaust pipe so I cranked the starter motor a few turns to blow it out and then all of a sudden there was a large amount of oil dumping from both the waste gate pipe and the main turbocharger exhaust pipe.

Background:
The engine has just been rebuilt and the turbocharger has been replaced with a new Comp Turbo Technology CT3693S (CT40) turbocharger. The reason why I replaced the turbocharger was because prior to the engine rebuild I had the same problem with the oil dumping out of the exhaust pipes so I presumed that the turbocharger oil seals were bad and might as well replace the turbo when doing an engine rebuild. Well of course I have the same problem...again...

Turbo Oil System Description:
Tapped off of the accessory case at the place where engine oil returns from the oil cooler is the location where the turbo oil system starts. Oil is fed under pressure through a fitting and a hose down through a bare aluminum Cessna one way check valve then vertically down through the turbocharger center section bearing assembly then the drain oil flows up through a hose and then into a pink Commercial Aircraft Products Valve Check Part Number: 340100 and then after that Commercial Aircraft Products the oil flows uphill to a Lycoming Adapter Assembly-Turbo Scav. Pump 29C21305 V5217 mounted on the accessory case.

The purpose of the aluminum Cessna check valve is when the engine is shut down that check valve is supposed to prevent oil from gravity feeding down into top oil feed port of the turbocharger bearings. I cleaned and inspected that check valve and it is operating normally.

The purpose of the pink Commercial Aircraft Products check valve is when the engine is shut down that check valve is supposed to prevent oil from gravity feeding down into the bottom oil drain port of the turbocharger bearings. I cleaned and inspected that check valve and it is operating normally.

The purpose of the oil scavenge pump is to suck oil up from the turbocharger and keep the oil from bypassing the turbocharger oil seals.


Troubleshooting Steps Taken Thus Far:
OK...the previous engine installation did not have this problem...until...I replaced the oil scavenge pump housing because there was a crack in the housing that was leaking oil. I found a replacement serviceable unit and installed that unit on the engine and then the oil dripping issue started...so it must be the replacement oil scavenge pump...

Prior the the rebuild I removed the return hose and felt inside to the impeller and turned the propeller by hand and I could feel the impeller moving so the drive gear is indeed mating with the accessory case gears and I verified that the impeller key was installed so the impeller was turning.

I ALSO conducted a test to see if the scavenge pump was sucking oil and this test was made with a bucket of oil under the airplane and the oil scavenge pump hose placed into the bucket and I ran the engine. The oil was draining out of the bottom of the turbocharger bearing as expected however the oil scavenge pump hose was not sucking the out from the bucket...

So I could not figure it out and then I decided to just have the engine rebuilt because the case seam was also leaking so I figured that...IF...there was something wrong with the replacement oil scavenge pump the rebuild shop would have identified the problem...or if...I had installed the oil scavenge pump incorrectly they would have most certainly have installed it correctly during the rebuild ...or otherwise found some broken part because they rebuild about 50 engines a month for over a decade so they know what they are doing...way more experience than me...

So could this oil scavenge pump be from a counter rotating engine???

Here are some pictures and a PDF of my troubleshooting steps thus far with comparison pictures of the two oil scavenge pumps side by side...

THANKS FOR YOUR HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 

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