The Son of Evil Beetle

henryp

Veteran Member
Joined
Oct 31, 1999
Location
The Great White North
TDI
1998 NB TDI
It had to happen sooner or later...

This past weekend my 1998 NB TDI suffered a Turbo Meltdown exactly the same way that Mickey's evil beetle crapped out http://forums.tdiclub.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=27&t=000009

The symptoms and conditions were the following: Full power upshift from first to second, followed by the engine "coughing" and a severe loss of power. I managed to limp it along for about 100 yards or so and then it stalled when I pulled over and let it idle.
I tried to restart it and it wouldn't turn over. If I'm correct, then it is hydrolocked.

Today I put it up on stands and removed the intake manifold, turbo and intercooler.

There were about two litres of oil in the intercooler, so it's just about certain that the engine is hydrolocked.

The turbine wheel looks intact and spins freely, but the compressor wheel is siezed to the housing and the compressor wheel nut came off. I retrieved it right in the air intake to the turbo. So if the turbine wheel spins but the compressor wheel doesn't, that tells me the turbo shaft is broken, right? We'll see.

(VW dealer wants $1493 (cdn$) for a new turbo and $1161 (cdn$) for a rebuilt one.)

Question 1: Do you think that the head gasket is intact after hydrolocking? I have not pulled the head off, and I'm reluctant to do so. I can evacuate the oil from the cylinders by removing the injectors and sucking the oil out with a vacuum pump. Any ideas?

Question 2: Anyone know a good turbo repair shop with the appropriate parts to fix a busted VNT-15???

arrgh!


henry
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
usually with the motor hydrolocked, the rods are all bent, they can be straightened and heat treated for a nonminal charge like $150/set. 19:1 CR or is it 18:1 on your model? Either way this is very high, it is much easier to lock this motor than a 9:1 cr gasser. I'd pull the head! Plus all manifolds really have to be VERY clean, as any little dirt is going to kill the new turbo. something the size of a BB will wreck the blades and even sand grain size particles can do major damage. turbos really need to be clean, clean, clean and IMO you just cant clean out the oil and install new turbo, you will just kill the new turbo too.

I'm new to diesels of course but have fixed many turbo charge cars and clean is not clean enough. spotless is the word. Good luck!
 
M

mickey

Guest
Mine hydrolocked without blowing the head gasket or bending rods. These motors are incredibly tough!

Your turbo shaft is, indeed, broken. Lots of luck finding one.
It's possible, though, that the turbo shop can fabricate a new one. They're not complicated.

Machining my compressor housing and installing a new wheel cost $300. I don't know what it would cost to machine a new shaft. A complete turbo is about $1200 at www.vwparts.com But first, I'd to go www.majesticturbo.com and give Robert a call. Tell him "Eric" from the TDI Club says hi! (And my turbo looks great!) Explain the broken shaft, and ask if they can machine a new one.

If you go the repair route, rather than buying a new turbo, they'll have to install a larger size wheel because they'll need to machine the housing. (Awwww...darn!
)

Good luck! I would strongly suggest that you remove the head and install a new head gasket, along with Raceware head studs. With the head off you can check the height of the different pistons above TDC (you'll have to, actually, to select a gasket) and you should be able to tell whether you bent a rod or not. There will be very tiny differences in height, but a big difference indicates a bent rod. You can also remove the oil pan with the engine still in the car and check for bottom-end damage. My guess is a new/repaired turbo and a cleaned out intake will solve your problem. Just be sure to get all that oil out of the cylinders!

-mickey

p.s. Garrett "VNT" repair parts don't exist. No how, no way. The only way to fix them is to adapt parts from different model turbos or to fabricate parts. That's why I suggest Majestic. They were the first shop that didn't just go "duhhhhhhhh......."

[ April 16, 2001: Message edited by: mickey ]
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
Agree, take the head off measure deck height, if they are all the same, rods are OK. I don't know if I'd take the oil pan off if the piston height is good, you did not seem to run the motor long, I would not think there is bearing damage? Anyway clean is the word! I mean real clean.

Mickey, give us the lowdown on you "BIG WHEEL".
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
I dredged up this thread from a month or so ago:
http://forums.tdiclub.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4&t=002521

My guess is that something went awry with the boost control system and the turbo went into an overspeed condition.

I noticed in the other thread that you've done the VNT adjustment mod ...

If it were my car, I would probably pull the glowplugs and get the engine spinning (do it by hand first, then crank it with the starter - it'll spit the excess oil out the glowplug holes), then check the compression and if any cylinder is abnormally low, it'll have to be torn down. Otherwise, plug the oil feed line to the turbo and see if the engine will start up (without the turbo, obviously). If it runs (which will get the excess oil out of the combustion chambers), then pull the glowplugs again, recheck the compression now that the amount of oil in there has been restored to normal. If these tests indicate that the engine itself is healthy, replace the turbo and get on with it.

Don't forget to thoroughly clean up the intake system before trying to start the engine. If the compressor wheel fragmented, the bits wouldn't have made it past the intercooler. And even if they did, and the bits did significant damage, it would show up in the compression test.

Brian P.
'96 Passat TDI mit UPsolute
 

henryp

Veteran Member
Joined
Oct 31, 1999
Location
The Great White North
TDI
1998 NB TDI
Mickey, thanks for the tips on checking the height of the pistons to check for a bent rod. I'll get going and do that.

And I'll definitely run the engine without the turbo on to blast any junk out of the head's exhaust ports.

Next stop is Majestic Turbo. Of course, I'll have to see if I can source a compressor wheel and turbine from an old VNT-25

Mickey - is this turbo hybrid a reveival of your dead turbo or is it a modification to your new turbo?

Well in the meantime there is work to do: remove the head, clean all the manifolds and other intake parts and buy replacement hardware, gaskets, nuts and bolts and other junk.

I wonder what caused the failure in the first place. Was it turbo overspeed? My VNT vanes were siezed (like Mickey's were) but I suspect that they were "baked" tight due to oil carboning after failure. Or was it the retaining nut that let loose? It was found in the turbo intake, suggesting that it may have come loose but not "off" until the last minute. IT was not inside the housing.
And why did the shaft break? It couldn't have been an oil problem (or could it?) Oil was definitely flowing - and no blocked oil passages in the turbo itself.



For the record: mileage was 143,800 km, oil used was Petro Canada Duron-XL 0-W-30 which was changed at 141,350 km. Mods include Upsolute Chip, K&N drop-in filter, VNT tweek. (Oh yes and a large lead weight that is usually attached to the top of my right shoe making it difficult to lift my right foot to slow down
)

henry

[ April 17, 2001: Message edited by: henryp ]
 

ScottTDI

Veteran Member
Joined
Oct 20, 2000
Location
Sierra Foothills, CA USA
Do you all think it would be worthwhile or too difficult to check the torque on this nut occasionally? We have seen enough of these failures to know that it is a Garret problem not a driver/mods problem. Even if a mod caused the turbo to overspeed (is that really possible?), the nut should not come loose.

Scott
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
Most turbo's the nut is torqued very carefully one time with lock-tight, then the unit is balanced by grinding the nut. Don't ever touch it unless you know what you are doing. NEVER.
 

henryp

Veteran Member
Joined
Oct 31, 1999
Location
The Great White North
TDI
1998 NB TDI
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Originally posted by Karl Roenick:
Do you think those were warning signs when the engine lost boost on your trip?<HR></BLOCKQUOTE>

Possibly - maybe the VNT vanes were sticking. But then again, the exhaust wheel looks intact. I'd just like to know what broke the turbo shaft. Mickey's wasn't broken. A local turbo shop suggested that maybe the bearing wore out causing the shaft to wobble. Perhaps it was a lubrication problem after all. Maybe Duron XL 0-W-30 is not the right oil for this application??


Intake Side is %$@^-ed


Exhaust side looks ok!

henry

[ April 18, 2001: Message edited by: henryp ]
 
S

SkyPup

Guest
Sounds like you might have had a bearing failure for lack of lubrication. The compressor wheel blow out could be secondary to that. Remove the shaft and look at it carefully, if it is darkened with bluing around the bearing interface, it was overheated, most likely from lack of lubrication or oil coking. If it is all bright stainless steel, then probably the compressor wheel lost a blade first and that caused the bearing failure and shaft breakage.

No way did the nut on the compressor wheel fall off by its own little self, something drastic caused that to happen.

There is a real good chance no pieces got through the intercooler into the engine intake since most of the large stuff would get caught in the intercooler and the small stuff would be in the oil. Of course, if the oil is in the pistons, then you'll have to clean out the upper end too.

Good luck, any more thoughts on what caused it?
 

GeWilli

Top Post Dawg
Joined
Aug 6, 1999
Location
lost to new england
TDI
none in the fleet (99.5 Golf RIP, 96 B4V sold)
Not a chance that it is the oil's fault alone. But then I have been warning people that if you decide to make a Skypup mobile or a Mickey Evil Beetle clone that you need to be running ONLY Amsoil Series 3000. But that said even at the limits I am impressed with this oil.

It has to be the sum of your mods (esp the VNT) combined with something else (failure like the colorado turbo).

The shaft could have broken just from teh compressor coming off. The fact that mickey's didn't break is something different I believe. not due to oil.

I have been saying all along though that if you choose this oil you should not do more than a few performance mods. Just chipping or Tuning box or something like that is probably okay depending on how you drive. This is only because there is a better oil out there for that and that is what Mickey had switched to.

Heck he was tooling around using a lesser oil (Chevron Delo Synth) than the PC 0W-30 Duron (IMHO) for most of the miles leading up to his failure.

the fact that the intercooler filled up with oil means to me that the oil was there doing it's job right?

is the intake clogged up? (ie was there lots of restriction in teh manifold?)

I am curious to see the answer to Skypup's latest question.

But this (to my account) is the second turbo failure due to a nut that we know of correct?
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
I don't see a problem with the nut flying off, if the wheel is frozen to housing and the other side is turning, then yes, it will just spin the nut off, even if the nut is torqued on correctly, the question is does the turbin wheen spin to tighten on loosen the nut (assuming the compressor wheel is frozen). Some do, some don't, some are just friction welded together and have no nut.

This is my seat of the pants list of turbo failures, that I've seen:
1) unknow, act of God, what can be said?
2) dirt, metal etc, sometimes if comes from a melted piston and blows apart the turbin, sometimes it comes from the intake, like a poor fitting filter. I should tell you guys not one single rice race that I know of has an air filter of any kind on their turbo. Most highend kits, can't even fit a filter on it. Like the Drag Prelude kit.
3) oil, but this is usually coke, and the shaft is really heavly cooked and the bearings show big time wear, this is a slow process and you start pumping oil out long before the bearing goes out. the carbon oil slinger has very little tension and a vibrating shaft just pumps huge quantities of oil out. usually the intake is filled with liquid oil and the car smoke like a old MB Diesel. This kind of bearing slop can also let the wheel contact the housing, I've seen housings milled away over a period of time by a wheel, most of the time the wheel does not blow up...
4) over speed conditions, or pressure surges. This for the most part breaks the wheel off the shaft. I've heard of wheels shattering, but for the most part the shaft sheers off and then maybe then wheel with the new found play blows up. I never seen a blown apart wheel still on the shaft, unless it was caused by a forein object. i.e. exhast valve head burning off and then shattering the turbin...
 

henryp

Veteran Member
Joined
Oct 31, 1999
Location
The Great White North
TDI
1998 NB TDI
Turbo update:

I performed an autopsy on the turbocharger last night, and here's what I found:

The shaft was indeed broken - seemingly at it's thinnest (and weakest) point. The turbine wheel seems to be intact, but because of the broken shaft, it is slightly damaged near its base.

The VNT mechanism is frozen (or baked) solid. I don't know if this was a cause or a symptom of the failure.

The compressor wheel is completely destroyed. Plus it's backing plate is also destroyed.

The turbo shaft itself is a nice blue colour, suggesting that there may have been some overheating. However, the shaft is not worn or scored. There were absolutely no clogged oil passages. The sleeve bearing itself was intact. The oil seals and backing plate on the compressor side looked like they were destroyed, but again, I don't know if this was a cause or symptom.

There was slight play between the turbo bearing and the shaft, but I don't know what the tolerances are supposed to be.

Here's one theory:
The compressor side oil seal may have given way partially, or the bearing may have been out of tolerance. I say this because I had noticed a bit of increased smoke onthe last tankful, but discounted it to poor fuel.
Eventually, the vibration caused by the oil seal issue or the out of tolerance bearing caused the compressor wheel or backing plate to break.

Hard to tell which event occurred first.

Oh well - off to the store to buy a new turbo.

henry
 

GeWilli

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Joined
Aug 6, 1999
Location
lost to new england
TDI
none in the fleet (99.5 Golf RIP, 96 B4V sold)
did i read it right somewhere else?

you've been towing a boat with this thing?

lord o mighty not only chipped tweaked tortured but towed?

Not as surprising now esp since valois says you got a code that indicated overspeed conditions . . .
 
S

SkyPup

Guest
<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR>Originally posted by Karl Roenick:
Are you sure it was overboost?<HR></BLOCKQUOTE>

Are you sure you did not mean OVERABUSE instead of overboost?


Blue colored stainless steel indicates SEVERE overheating and lack of lubrication. The stainless steel should be bright shiny stainless steel, indicating that it has never exceeded 1000* or so, if it is BLUE, it has exceeded 1,500* and toasted itself into destruction.
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
would seem so. A good build up for towing would be something that get rid of pumping losses and heat.
Down pipe, TT exhaust, louver the hood at the rear, or off set it up 1/2 inch and yank all the weather stripping, accusump to the turbo, idle cooldowns (never liked the turbo timmer), find a 280Z turbo cooling fan and hook it up, maybe an intercooler fan, 110 injectors, maybe a bigger compressor, maybe a lower CR 18.5, water injection, propane, new intake and intercooler tubes?

I would not do a chip or TB, as both may or do widen the injection pulse which will tend to add heat build up during towing, just some thoughts. Also I was a big time Dodge guy for many years and most VNT's failed due to gunk build up on the vanes, leaving them frozen and forcing the turbo into a permanent overboost/overspeed conditions.

I'm not knocking chips or TB, I saying for this setup, getting rid of heat and stopping pumping losses, what you don't want is to up boost or lenthen the injector pulse width. Yes I understand that the thermal load of increased boost maybe less than at stock boost (given exact same inector pulse), I still think there is a work load imposed on the turbo at the increase boost that may be bad for long term towing.
 

Karl Roenick

Top Post Dawg
Joined
Sep 22, 1999
Location
Clifton Park, NY, US
Would removing the turbo at 100k miles, giving it a cleaning and (big maybe) new bearings, etc be worthwhile?

Does anybody have that link to the pictures that the guy from Europe made who was converting his turbocompressor into a gas turbine (I think)? He had some gunked up vanes.
 

valois

Banned
Joined
Jan 11, 2000
Karl, we archived that thread, it should be under the maintenance archives, I would think cleaning the vanes would be an excellent idea.
 

GeWilli

Top Post Dawg
Joined
Aug 6, 1999
Location
lost to new england
TDI
none in the fleet (99.5 Golf RIP, 96 B4V sold)
am I wrong? aren't these VNT turbos running with hydrodynamic film bearings? IE oil bearings?

not ball bearings, right? that was a fair bit of sludge in teh intake the exhaust side could be looking much worse than the one that was taken apart!
 
S

SkyPup

Guest
Karl, you are totally confused about VW TDI turbochargers, the vanes are NOT gunked up, they are always nice and carboned that way. Plus the VNT Dogdge turbos OldMan refers to are all on much hotter gasoline engines twelve years ago when the first Garrett VNT turbos were produced (only 2-3,000 then compared to 3,000,000+ now).

You need to take home a VNT Term Paper and do some reading to educate yourself better so you have some idea about what a Garrett VNT15 turbocharger on a VW TDI really is.

Here is Tom's nice link to his gas turbine experiments for you edification:

http://www.technologie-entwicklung.de/Gasturbines/VNT15-Turbo/vnt15-turbo.html
 
S

SkyPup

Guest
Garrett VNT15 Mechanical Design & Performance

An actuator rod is attached to the external crank and translates rod movement into vane position change. The external crank and crank fork are joined in a fixed position onto a adjustable common shaft between the compressor and turbine housings. The crank fork engages the upper unison ring, which rotates in both directions concentric to the turbocharger rotor centerline. The unison ring adjusts all the vanes simultaneously, which rotate inside a nozzle ring, by engaging the vane "arms" which protrude outward from the opposite side of the ring. The nozzle ring assembly is spring-loaded against the turbine housing, with spacer pins in-between to assure correct vane side clearance. This arrangement allows the nozzle ring assembly to follow turbine housing thermal deflection without change in vane side clearance. The spring disk and tube seals the mechanism cavity against exhaust gas combustion by products. An actuator mechanism spring keeps the vanes in a fail-safe open (low boost) position in case of system failure, To ensure that the turbocharger operates within acceptable limits, tamper-proof calibration screws are used to set minimum and maximum vane opening positions.

The VNT15 mechanism has to function in a high-temperature, corrosive environment with non-lubricated surfaces expected to maintain minimal frictional losses and wear over the product life cycle. Selected alloys in cast or wrought form containing cobalt, nickel, stainless steel, and others perform well under these adverse conditions. The vane control mechanism is composed of movable cast stainless steel vanes mounted on the nozzle ring, which is composed of high chromium iron bearing material for temperature and oxidation resistance.
The vanes are free to turn on this ring by means of "arms" welded to each vane, which protrude outward from the opposite side of the ring. A grooved "unison ring", fine blanked from a precipitation hardened, austentic stainless steel, adjust the vanes simultaneously. This unison ring floats on six independent roller bearings which are located between the vane arms and the which ride on the fixed nozzle ring. Foreign particle deposits which might jam the mechanism are not a problem due to the "sweeping" action of the vanes themselves. Particles that begin to collect between the vane and nozzle ring are continually swept free by the continual movement of the vanes.

Along the lines of constant engine speed, air/fuel ratio increases more or less linearly with pressure ratio.
Exhaust temperatures are also speed dependent. Constant peak firing pressures in the VW TDI engine also increase somewhat linearly. As speed increases at constant boost, peak pressure decreases for the same combustion kinetics reasons that produce smoke, and because the effective fuel stroke (volumetric efficiency) of the BOSCH VP VE 37 fuel injection pump is dropping off. At low boost, below about 1.8 pressure ratio, the air/fuel ratio is so low that combustion efficiency is severely reduced. However the engine performance improves through the high-boost, low-speed range with the increased air/fuel ratio. This area is the area where the VNT is very good at, remembering that adventuring with higher air/fuel ratios flirts with peak firing pressure limits. Care in matching this with VNT nozzle control is necessary.

The control device of the VNT15 is the nozzle opening and the mechanically available nozzle opening has been carefully calibrated. A variable rate actuator opens the vanes at an initially low rate until the engine reaches a predetermined boost, whereupon the vanes begin to open at a much faster rate.

To best utilize the VNT turbcharger, several considerations must be addressed: How well does this turbomachinery match this engine? What are the service requirements of the engine and especially where is the bulk of the fuel burned in the vehicle/engine duty cycle? Different countries have different driving cycles which profoundly affect the optimum match of the VNT15 to the VW TDI engine. Obivously, the most common useage of the engine needs to be considered during the TDI-VNT match so that the appropriate turbine design point is chosen.

The present control system uses the measured "error" between actual boost pressure and a "desired" boost pressure found in a pressure map in the BOSCH ECU. In steady-state operation, this never results in negative or adverse cylinder pressures. It does in transient operation, however, so an adjustable limit is included in the control logic of the ECU for VNT override. The software then allows various combinations of rates, coefficients and proportional, integral or differential operators to be used to control the VNT.

The greatest steady-state VNT15 operations are derived at low engine speeds. By overplotting islands of best turbocharger efficiency and integrating the final use of the engine the optimum match of VNT to the TDI engine is achieved.


When compared with the turbine of the A3 TDI GT15 fixed nozzle geometry with wastegate, the new A4 design VNT15 offers a significant increase in available turbine flow range for any given operational point of the TDI engine. As an example, the new A4 VNT15 unit demonstrates a third gear WOT acceleration from 1,500 RPM to maximum (simulating a passing event) reaching full boost 30% faster than the older A3 GT15 design. Similar results of a WOT launch from idle are seen.

 

Karl Roenick

Top Post Dawg
Joined
Sep 22, 1999
Location
Clifton Park, NY, US
Thank you for the link and educational words Skypup.

Thomas does write:
(before assembly): "I noticed, though, that the NGV actuating mechanism was rather stiff, if not to say stuck (at this time yet I didn’t know why)."

(after assembly): "Now that the turbo’s cleaned and reassembled the NGV actuating gear works much smoother."

What could be done, say at 100k miles, to extend the life of the turbo? What kind of tests can be done? We can check how easily the vanes work without taking anything apart, I think. Could oil pressure readings on the turbo oil lines indicate an impending failure? How much would it cost to rebuild a turbo at, say, 100 k miles? Would it involve changing out the bearings, cleaning out oil passages, cleaning the parts, and what else?
 
M

mickey

Guest
Henryp: Your "autopsy" sounds EXACTLY like what I found in my blown turbo. Every single detail is precisely what I found. I believe one of your compressor wheel blades fatigued and snapped off. That would severely unbalance the turbo. The hardened steel shaft won't tolerate vibration at those kind of speeds. It'll snap very quickly. That causes the seals to separate from their seats, and oil pumps out under pressure.

-mickey
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
Yes, I agree, lots has happened since the 88 VNT Shelby cars, however, I read the same VNT, hype at that time also (1987 ish), I can dig up the turbo mag article later (1987 ish)? I'm not saying lot more engineering has gone in and for sure 3 million TDI (how many are VNT?) is a huge sample size. I am saying the VNTs were hyped before and passed some sort of QA before reaching production, where a good number did in fact fail in service. I said good number as these were low volume to begin with, all the ones I know of failed, but of course I can't say "all". My two original GLH-S with T3 ran well over 100,000 miles before the turbos were upgraded and were putting out far more than the stock 12.5 PSI for the entire time (17 to 22 PSI). Same company, same motor, just different kind of turbo.

That said, I would still be leaning toward removing pumping losses, getting the best oil and cooling the stuff on the next go around. Just to be real sure.

It is hard to compare a TDI in America to a euro spec one, as we have far poorer fuel, I would not be surprised to find things like the sulfer in the fuel eating into the metal, higher exhaust temps due to emissions, and all kinds of other problems that just did not come up in Germany. Toss in a bunch of after market parts and then towing, I'm sure we will all agree that Henry is almost like his own R&D for TDIs.

I'm not knocking VNT, as my A4 performes better than I ever thought a diesel can perform and then some. I do have concerns about the vanes on Henry's VNT being frozen. Sure he is towing but I can't help wondering is this a towing, raised boost, lengthen the fuel map combination failure. H

Henry, what is sticking the vanes? is it all the burned oil? is it a piece of metal left from the compressor? Baked on soot? Warp backing plate?
 

valois

Banned
Joined
Jan 11, 2000
Hey Oldman, you are in good company, both BG and myself are previous GLH owners, Man I loved that little car, and meanwhile GM was producing it's 305.
 

Oldman

Top Post Dawg
Joined
Feb 3, 2001
Location
Leander,TX,USA
Mickey, I don’t know about that, you would think when a blade snaps off the unbalance would vibrate the shaft and it would be the copper (or whatever) bearings that get whipped out as bearing is a much softer metal. This is a higher heat, high boost setup, could the higher heat close the clearance down between the wheel and the housing, friction welding the wheel to the housing causing the shaft to sheer? The shaft has been already weakened by repeated extended thermal loading.

I’ve stated that no Honda racers that I know of run any sort of air filter and broken blades are common among the group, I can’t think of one that failed in the above way due to a missing blade Unbalanced or loose clearance turbos, pump lots of oil and kill the bearings. But refer to above, I have stated most failures really have no know single cause. Hey, I’ve worked on turbos that you can rock the shaft, they still can put out boost! Sometimes even over 20 PSI, but they pump a huge amount of oil. The walking compressor wheel mills itself into the aluminum housing! But like I said, still work..
 
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