1st start

[T41pilot]

Did my first start on my Turbo Aerovee yesterday and things did not go as well as hoped for. Oil leaked out of the front cover of the oil pump at a pretty good clip even though the cover had been torqued to the 14lb spec. Had another pretty good leak at the turbo mini sump. Not really surprised there. RTV did not seem like the best idea for mating the surfaces but I followed the manual anyway as I have done throughout the project. Have since made a gasket for that and that cured that leak. The cover still leaks after removal, cleanup and reinstall. The real icing on the cake and apparently a major deal breaker is that a substantial amount of oil is getting puked into the exhaust pipe. I've only run the engine a couple of times for just a minute or 2 while my crew were looking for problems. I never ran the engine past 1500 rpm. My indicated oil pressure was 50 psi on the first run. Today I started the engine again to play closer attention to the oil pressure. Again I only ran the engine a minute or 2 before oil was puking out the exhaust again. Oil pressure indicated between 38 and 40 psi on this run. Those numbers certainly are not high but my crew are guessing the seals in the turbo are no good. I removed the exhaust from the turbo and sure enough, the turbo was covered in oil on the exhaust side. I could understand if the oil pressure was sky high you could blow a seal anywhere in the system but it was never above 50. I had to reclock the turbo to make it fit correctly during the install. Could the seal have been mechanically damaged during that? Can a seal just dry out and be no good from sitting on the shelf for 3 or 4 years? My oil lines are plumbed the same as shown in the turbo retrofit manual. I'm in the process of pulling the turbo out right now. I'm sure it needs to be looked at somehow or replaced. If somebody could enlighten me with an explanation of what my problem may be and how the oil makes its way through the turbo housing and seal system it would be most helpful. I'm starting here because there are long lead times at sonex for most anything right now.

[Bryan Cotton]

Congratulations on your first start! I don't have the turbo but my motor leaks like the Exxon Valdez. I suspect I'll be chasing leaks for a while. I'm jealous of your oil pressure, mine is around 80 psi.

[Waiex 0194]

Those three leaks could be related. The front pump scavenges turbo oil and keeps the return line from the turbo below ambient pressure. If the outlet of the pump was restricted, the unmonitored pressure would climb until it found a way out. This could also cause the turbo oil outlet pressure to be the same as engine oil pressure, which would get past the turbo’s labyrinth shaft seals. If these thoughts have any merit there should be engine oil in the intake tract as well.

[T41pilot]

Thanks Larry. I've pulled the turbo out to see if anyone can inspect it for me. I can pull the hoses to make sure they aren't plugged or something. There are no sharp bends in their routing to cause problems. What you said makes sense to me. Could I perhaps connect the turbo supply and drain hoses together and just crank the engine to see if oil is dumping back into the engine(near the top of the engine under the oil cap area on my engine) as a means of testing the pump? As a final thought, if my Turbo inspection finds nothing unusual, it would most certainly be a drain side through pump problem by the sound of it if I understand you right. Is there such a thing that you can put too much lithium grease in for priming when you put together the pump and plug it that way? Thanks for the help.

Regards

[Rynoth]

I can think of only 2 places oil could get into the exhaust. Through the turbo, or through the cylinders (past the piston rings and out the exhaust valves.) Is there oil in the exhaust pipe pre-turbo?

Larry's thoughts are good and a definite possibility. Re-clocking the turbo would not have affected the oil seals. I have disassembled my turbo in the past, the interface between the intake/exhaust sections of the turbo to the core have no relation to where oil passages are. The oil gallery is entirely internal to the core.

One thing I might try as an experiment (while you have the turbo out of the engine) is to force some pressurized fluid (oil, mineral spirits) with a syringe into the oil inlet on the turbo, and see where it comes out. Might be a pointless experiment but could show something. Might not be able to replicate 40+ psi though.

Your test of the scavenge pump is sound (determine if it's actually scavenging oil) if you can find a way to do it safely without too much of a mess.

[T41pilot]

Thanks for the reply Ryan. The oil in my exhaust appears to not be combusted at all and the engine starts right up so my 1st guess is the problem is on the turbo side of things right now. It's hot as all get out today, so I won't be going to the hangar but I'll see if the exhaust manifold is dry at the turbo attach area tomorrow. I brought the turbo to a friend who has an A&P buddy that said he might be able to have a look at it if it was a turbo he was comfortable taking apart. In the meantime, I'll look at the pump circuit and try to determine if something is wrong there. Is it possible to assemble the turbo side of the pump upside down or 180 out so that passages don't mate up? I don't remember at this point since it was assembled so long ago. It was puking a lot of lithium grease out the front cover on the first run. Seems like you need a lot of pressure to do that. If the A&P decides he doesn't want to look at the turbo, is it rocket science to take it apart and have a look myself?

Regards

[Rynoth]

If the A&P decides he doesn't want to look at the turbo, is it rocket science to take it apart and have a look myself?

Regards

It's not rocket science to separate the 3 main parts of the turbo (intake housing, exhaust housing, core), but it can be tricky (and potentially dangerous.) The only difficult part is removing the big hefty snap ring on the intake side. I had to modify the tips on my (strong) snap ring pliers have enough access to get it out, but if that thing snaps free it could be nasty. Wear eye protection.

There won't be much to see though and probably wouldn't help your troubleshooting. The compressor/turbine blades are part of the core, all you would be removing is the intake/exhaust housings. This is what the core looks like with the housings removed: https://i.ebayimg.com/images/g/2-AAAOSw ... -l1600.jpg

I actually (destructively) disassembled an old core out of curiosity (took it completely apart.) Don't do that unless you're going to throw it in the trashcan afterwards, it would likely void any sort of warranty repair and throw off the factory balancing. But I will mention that the nut on the compressor side of the shaft is left-hand threaded (found that out the hard way.) I would doubt that an A&P would mess with turbo core internals, seems like more of a factory thing to me.

The more I think about it the more Larry's thoughts make sense. Definitely investigate the oil pump (and pump to crankcase oil path), if I recall the pump is disassembled/reassembled during the engine build, with potential opportunity to get things wrong. Check your Turbo return oil lines to be sure they are free of blockage (you know oil is getting to the turbo because the sump was leaking). In particular, be sure the pump-to-crankcase return oil is truly able to drain freely into the crankcase and isn't actually ending up in some kind of void with no escape.

[epeachey]

I had a similar issue with my turbo pushing oil Kerry's response below
It may be that your oil pump is not scavenging the oil from the turbo as it should be. I will forward you information on wat to check and how to correct the issue if it exists.

Dear AeroVee Turbo Customer,

We have recently learned that a small batch of AeroVee Turbo oil pumps (ACV-T05-47) were shipped with one of the two required oil passage plugs missing. You are receiving this email because your oil pump could be affected, causing low engine oil pressure.

If your pump is missing a plug, you can easily install the missing plug using the following pictures and instructions, or you may send your pump to Sonex for installation of the plug at no-charge. Only the forward half of the pump will need to be sent back for service work. Please contact tech@sonexaircraft.com to request and obtain an RMA number before sending back any parts.

Service Work Instructions:

[T41pilot]

Thanks Elwyn. I sent you a PM.

[T41pilot]

It appears that after talking to Kerry at Sonex, that one of the ports on the turbo side of my oil pump was never drilled out. He indicated that they saw one instance of this and thought it was a one off. Apparently not. I think their incident was on the input side of the pump. He sent me a picture and said to make sure the gears were visible through the hole and that the hole could just be drilled out if it wasn't there. My problem appears to be on the output side of the pump. There is a dead end there. No path to the center of the pump. I'm waiting on a response from Kerry whether this side can be drilled out to the center of the pump. Does anybody here have a turbo pump that isn't installed yet to see whether that hole is a straight shot to the center of the pump like the input side is? I tried to submit a picture of the interior of my pump but the board just hangs up and I can't send a message. Probably a resolution issue with the picture.