Turbo grief!
 

2 years of sweat, rebuild everything but.... that rear wastegate.

On the third flight I lost boost and went to 27" at 2000 feet. First thought... stuck open wastegate. Landed. Nope it moves freely. Spun the new turbo... yep spins nice. Check oil pressure to the waste gate...... good as it gets... no exhaust leaks.... no induction leaks that I can see....

question: The wastegate is original 3000hrs. It was adjusted, but looked pretty worn. It that the most likely failure point? Have you ever heard of one going bad? Where else can I look? How big of an induction leak would be needed to loose that much pressure? How big of an exhaust leak would be needed to cause zero boost?

I also capped off the return line to the wastegate so that off idle I would have fully closed the wastegate. Started the engine and nope 28" is all I can get out of it. Assuming that the exhaust and induction are in good shape, is the turbo and wastegate the only places to look? If the turbo spins freely and smooth, would that rule out the turbo?

Thanks

Richard

P.S. Performance is AWESOME!!!!!

2400 rpm, 22" clean, at sea level, gave me 150-160mph. Can't remember if that was good, but sure felt fast.

Richard,

You could have some debri blocking the inlet orifice of the wastgate actuator... have you tried back-flushing it? Remember now, the oil line comes off the bottom of the accessory case and the oil pump... and this oil is unfiltered.

Is this engine newly overhauled or what?

SkyKing

New engine.

I did clean and backflush. Then when I capped the return line and started the engine I did get full movement out of the wastegate. So it's closing.

turbo problem
 

I just replaced the front turbo on my bird for the same reason. Found that the exhaust turbin was rubbing in the housing. Would spin free with my hand but when we pushed onthe compressor side it moved back enough to rubinthe housing. According to my overhaul manual on the turbo there should be nomore than .003 movement in the turbo. Mine had .009 and only would move with a lot of pressure. My mechanic felt that under high power the exhaust pressure would move the turbine in the chambers causing it to rub and slow down. After the new turbo was installed I have not had any more loss in power. Hope this helps

Bob

Bob, I think you were trying to describe "axial" play of the shaft, and there shouldn't be any, except the minimum spec which you addressed.

As far as Richard's problem, if the wastegate closes completely with the return line capped, then the problem might be one of two things: either a faulty pressure relief valve, or the controller is not right or improperly rigged. The engine should go to full boost at about 2/3 throttle if everything is set-up correctly.

Richard... was the controller newly overhauled? I understoof or presumed the engine WAS performing just fine -- and THEN something apparently occurred where you lost boost in flight. Are all the hoses secure?

SkyKing

I capped the return line "pre" controller. Bypassing the controller completely. Yes, it was performing perfect for the first 3 hours. This is a brand spanking new turbo. Right out of the box too. I don't think I have excessive axle play, but something I plan on measuring today. Way I see it. Since I've bypassed the controller, going to full boost off idle, and verified shaft throw on the wastegate. I've either got one of four problems. Wastegate butterfly valve has collapsed, turbo is capuut, induction leak, or exhaust leak. Am I on the right track?

I would lean tward the wastegate valve going bye bye, since it is the oldest component on the engine. Have you ever heard of such a thing?

Richard

Turb problem
 

Richard, I would look more in the area of exhaust or induction leaks. Have you tried hooking a leaf blower to the manifold and with soap and water check all connections. Simple to do and not expensive. Only pulling 27 inches sounds like a pretty big leak and you should be able to find it quickly.
good luck
Jerry

It was the turbo. Manufacturer flaw, thrust bearing wasn't secured on the compressor side. Allowed it to fall out and end play was enough to gawl up the housing. Now I know what the Skymaster performs with a seized turbo.

Richard,

Inquiring minds want to know: Which shop did the overhaul on this turbo anyway? Are you saying that the nut on the impeller-compressor came loose? I can't imagine a shop not torquing the nut on to specs!!! That COULD have caused a lot of internal engine damage if had really come apart. Whoah!!

And now the fun part... that rear unit isn't the easiest puppy to get in and out.

SkyKing

The shop is being nice to me so I'm going to leave the name out of it. I'm not sure, something inside the center section was loose. Not that easy to get out... yes. True. Had to remove the lower skin. Got it removed and another installed in one day.

Well, I can see why! One-day service turn-around. Now that's what I call real 'AOG' service!!!

SkyKing

Interesting. The same thing happened to me a few years ago (not the same defect in the turbo, just the broader concept of a defective turbo out of the box). This was a brand new turbo from Cessna (ouch) because the turbo before it self destructed in the way Skyking descrbed and sprayed metal through my front engine. That was what caused my only power loss in a 337, and my overhaul. So anyway, when we put the new engine on, remans do not come from Continental with a turbo, so we had to buy a new turbo (no core to give Main Turbo, or whomever). And that new turbo would not deliver pressure, I never did pay attention to why, because we got another one under warranty. I was thinking of mentioning this during this thread, but it seemed like such a bizzarre case that it was not worth discussing. I was wrong about that apparently...

Kevin

Those yellow tags don't mean much I guess.

Hired hands...
 

It seems real difficult to hire a good hand these days and it's gotten to the point that if you don't do the job yourself, it never does get done right. Everybody seems to be cutting corners... and quality of workmanship doesn't happen when it's a hurry-up and get-it-out-the-door thing. And some shops, with inexperienced people working on rather complex systems like the turbocharger set-up who don't understand have been known to misdiagnose a problem and repeatedly send a perfectly good part, like a controller, out to a distant repair/overhaul facility, costing the owner big time... when the problem all along was a small carbon particle blocking the inlet orifice to the wastegate. But do you think the shop would rectify the 'problem' they created? NOPE! It's part of their 'troubleshooting.' And that's why it's best to have a retired IA work with you on your plane where YOU take responsibility for getting the job done. Yah, their are exceptions like having to send out a turbocharger or whathaveyou, but the majority of things can be accomplished with a little common sense. That too seems totally lacking in most shops.

SkyKing

knew of a guy to install the oil lines on the tee fitting wrong.
One nipple has a restrictor in it, the other does not.The turbo will last about 30 min. if hooked up to the restricted side. poor guy bought 3 turbos before he figured it out.

You're right on Skyking. I've seen some quality shops in Portland go from great work to "best guess". Flying back several times to a shop just to get a simple thing fixed, and fixed, and fixed. You're right, they cut corners. I can understand why though. It's quite clear. It's all a matter of "financial crisis". The owner is pressing the A&Ps to get the job done cheap...... "Get it done" Shops are competing for what little work their is in the GA world, so they bid low.... Then comes the expensive part.... the parts. Jacked up pricing on the parts leaves the shops with little room for what should be important.... the labor. You can make a really nice part into a crappy one in the "wrong" hands.

Doing it yourself seems to be a growing tend. (One I'm VERY happy about personally) Don't get me wrong. I love the people in the GA matanence. Great people. They just have their hands tied. I think it's refreshing to see people figuring out for themselves, they CAN do the work. They CAN use their own ideas, and with a little QC from friendly A&P's IA's. The work really turns out nice. I've seen some "non approved" work on planes that just make you say.... "Dang, why didn't they do that long ago."

What we are facing is an extinction of GA. Kit planes out sell certified planes (best guess) 100 to 1. Why? Because, if I put a newer tach in my plane.... who cares! I personally know of two skymasters who have been down for almost a year now because of one silly, stupid, unexplanable event..... they are needing a tach. Can't get them rebuilt anymore, can't find used, can't find a "approved" replacment. That's just silly. If GA is going to survive at all, things HAVE to change. If we all just sit and take it, your skymaster might as well be converted to a lawn mower.

Did you know the adverage age of an A&P is over 42 years of
age!

Sorry, didn't mean to get off topic. Just my sensitive side.

New turbo is really working well. Flew 5 hours today just to break it in. New one is much more effcient than the older one.

I think a large part of the problem, although I don't like it, is that the mechanics are paid so poorly. None of us wants to be paying more in what is already a fairly expensive activity. But a guy expected to know what they need to know to properly troubleshoot, repair, and work on aircraft - and to take the responsibility required, and the time needed to build experience even in some of these more obvious things - while getting paid under $20 and hour, even after years of experience...well...

I think that part of the overall problem is pretty obvious.

general turbo thoughts
 

i've run turbo skymasters for 20 years. living in colorado the turbos get used! the wastegate controllers tend to coke up when the shafts wear. with 3000 hours i would bet the shats are worn. you can use a copper based lubricant periodically or have the wastegate overhauled($s). i also have had problems with the turbo controller, it seems a lot of shops don't know how to correctly overhaul them. eventually i found someone at firewall forward in ft collins, co that knows what they are doing. what i have noticed over the years is that shops in the mountain areas know a lot about turbos and oxygen systems because a lot of aircraft have them. sea level shops just haven't seen that many. as far as induction leaks, i had a rubber coupler come completely loose and still got near full boost at 7000 feet. the turbos are a bit overdesigned.

turboooooo
 

Richard, that's why I mentioned ealier in the thread about checking the turbo. I've had both supercharged and turbo aircraft and when you told your problem, it was identical to the one I just went thru. My mechanic said right away that it was the turbo on my bird. It doesn't take much to shut down them compressors.

Bob

VAPC & Turboshaft coking...
 

Bruce,

Just to make sure we're all on the same page here... are you saying the variable absolute pressure controller (VAPC) up top side tends to coke up when the main turbocharger shaft cokes up, or that the wastgate itself cokes up? As you know, the oil line from the engine to the wastegate and on up to the controller (VAPC) is totally separate from the oil line that lubricates the turbo shaft.

We have a 1200 hour TSIO360(C) that's producing a little carbon and of course flecks get stuck in the wastgate inlet orifice, which will cause zero boost until enough oil pressure overcomes and forces stuff out of the way... but that orifice is pretty tiny and since unfiltered oil is taken off the bottom of the accessory case to drive the wastegate actuator, this can be a continuing headache as the engine ages. Carbon can also block the controller. It's a many 'splintered' thing!

SkyKing