Jump to content
Ultimate Subaru Message Board

Recommended Posts

So I got a head scratcher here.  Need some other brains to think of possibilities here.

 

Backstory :   04 Forester XT.  Unknown history, but overall in good shape, 145k miles, ran well except for a large amount of black smoke and lacking full boost.  Removed Turbocharger, it had lots of obvious shaft play, bearing and seal failure.  

 

Took the turbo to a local, reputable turbo repair shop.  All they do is reman turbos, mostly for diesel trucks and semis, but they do smaller gas turbos too.  They rebuilt our turbo using a pre-assembled and balanced shaft assembly supposedly from a reputable european company.

 

We installed the turbo on the car.  Ran good for about 1/4 mile then started making bad sounds and boost was intermitent.  Turbo sounded awful, so we remove it again.....heres where it gets weird.  THE SHAFT NUT WAS MISSING!   it had spun loose and then gotten sucked through the turbine and was found in the intercooler.  damaging the turbine.

 

So we take it back to the turbo shop.  They are confused, first saying that it must be an issue with the engine.  Insisting it must be backfiring.  Well, it wasn't....ran smooth as butter, no CEL.  We verified oil feed to turbo while engine running, and engine was not backfiring.

 

Anyhow, they get us another shaft assembly and housing and reman it again.  We install it.  This time there was alot of smoke on start up......we figured some coolant/oil fell down the uppipe upon the last removal.  So we warm it up, take it for a test drive.  This time it did well for about 2 miles.....then same issues again.....noise, loss of boost.   Remove turbo again......SAME ISSUE!!!  the nut has spun off....this time it got kicked forward into the plastic intake tube that runs under the IM and stayed there in a groove in the tube.

 

So we go back to the shop......Shop owner is apologetic and confused.  His lackey was more rude, insisting that "well that engines eaten three turbos, somethings wrong".  While in a sense that's true, I point out the the first turbo indeed had failed bearings, but its shaft nut stayed in place.  Asked if he's ever seen a turbo fail and the shaft nut come off?.....He scratches his head and then admits "No".   So even if there had been an oil failure, that doesn't explain why the nut came off.  

 

Additionally, the lackey said "I checked the torque on that before it went out"  This made me alarmed, because when I brought the second failed unit in, he had begun trying to fit the nut back on the shaft by threading it right hand......except this is a left hand threaded unit....specifically to keep the natural rotation forces from loosening the nut!  He seemed to not know this!  But then pretended that "oh yeah, I knew that" when I called him on it.  In fairness, their shop is filled with literally hundreds of turbos for service of all sizes and types, and they do have a stellar reputation in the area.  Hard to tell what's BS and what's not.

 

They are going to order parts for one more, and this time the shop will disassemble and reassemble and re-balance the unit themselves to verify.

 

They have asked me to verify oil pressure.  And any other possible engine issue.  

 

we are about ready to demand our money back, take to small claims etc....and just buy a genuine Subaru reman for a few hundred more.

 

My question here is 

 

a)  has anyone seen this type of failure, nut coming off?

 

B) Is there any possible way that the VVT system is taking oil feed away from turbo when it activates?  They do share the same banjo fitting feed off the passenger head. (BTW, I checked the screen it's a-okay)

 

c)  Is there any way a fault in the tumble generator system could cause back pressure in the intake similar to a backfire (but this engine is not actually back fireing, and there are no CEL codes)

 

turbo experts rack yer noggins!  

  • Like 3

Share this post


Link to post
Share on other sites

I have never heard of that issue before.

And I have taken a turbo off My 04 Baja, and rebuilt it including removing and tightening that nut. And had no issues 10k miles later.

 

Though there is a TSB about removing the screens in all the banjo bolts. Both AVLS solenoids, as well as the turbo one (I think)

 

Though even if they were restricted, hard to make a connection between lack of oil and the nut coming loose. That doesn't make sense.

 

Imo, sounds like the rebuilder screwed up twice.

Share this post


Link to post
Share on other sites

checked the banjo screen and it was clear.  

 

Mounted MAF directly to the throttle, looped coolant lines toghether, and stuck a bolt through banjo fitting that bolts to turbo to block it off, and ran engine without the turbo.  It ran fine.  No smoke.  No misfires, no CEL.

 

Cracked loose the bolt on the banjo and oil pushed out with gusto.......Pretty sure there is good oil to turbo, but going back to the car and putting a gauge on it later today to confirm with a PSI number.

Share this post


Link to post
Share on other sites

You've searched Nasioc? If it's happened it's covered there.

 

Found this RE: torquing that nut. This is on the STi IHI VF39 and not a stock Mitsubishi TD04....different brands may be different specs:

 

"Two drops of red loctite, 28" pounds (not foot pounds) and then an additional 1/8th of a turn. It is a torque to yield. It is also a good idea to do this twice, to make sure that you have taken the slack out. Let us know if you have any other questions or if you need anything else."

 

 

Those stock TD04's seem to last <150K miles, so likely the original was just old. I'd call PRE - if still around - and see what they think.

Share this post


Link to post
Share on other sites

pb127111_0.jpg


If a turbocharger has failed due to oil starvation, there are
several key indicators to investigate. Firstly, if the compressor wheel nut is
missing, this is a clear indication of main shaft seizure. This may be
categorized further by the micro-welding of the main shaft to its housing,
locking it solid. 

 

from 

https://www.delphiautoparts.com/en/toolbox/turbo-failure-modes-oil-starvation

 

Mahle says the same.

https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs/catalogs-and-literature/turbo-damage-brochure-mo-2-612.pdf

The shaft might suddenly become blocked in the bearing housing due to the mixed friction. If the rotating assembly is suddenly blocked, the locking nut of the impeller can become loose.

 

I`ve never seen it,but,it sounds reasonable.

Edited by naru

Share this post


Link to post
Share on other sites

 Well, verified 80 PSI at idle, 95+ PSI at 3500 rpms AT THE TURBO line.  

 

REMOVE THE BANJO BOLT SCREEN!  There is a TIB for this.

 

tsb is to replace the screen, not remove it. I didn't replace but the OE screen is clear and flowing....See above oil pressure readings.

 

You've searched Nasioc? If it's happened it's covered there.

 

Found this RE: torquing that nut. This is on the STi IHI VF39 and not a stock Mitsubishi TD04....different brands may be different specs:

 

 

Those stock TD04's seem to last <150K miles, so likely the original was just old. I'd call PRE - if still around - and see what they think.

 

Original did not lose the nut.  Only the 2 replacements did.  And they did it within a couple miles.

 

 

pb127111_0.jpg


If a turbocharger has failed due to oil starvation, there are
several key indicators to investigate. Firstly, if the compressor wheel nut is
missing, this is a clear indication of main shaft seizure. This may be
categorized further by the micro-welding of the main shaft to its housing,
locking it solid. 

 

from 

https://www.delphiautoparts.com/en/toolbox/turbo-failure-modes-oil-starvation

 

Mahle says the same.

https://www.mahle-aftermarket.com/media/local-media-north-america/pdfs/catalogs-and-literature/turbo-damage-brochure-mo-2-612.pdf

The shaft might suddenly become blocked in the bearing housing due to the mixed friction. If the rotating assembly is suddenly blocked, the locking nut of the impeller can become loose.

 

I`ve never seen it,but,it sounds reasonable.

 

 

Shaft on the second reman looked nothing like the above worn out chewed up one.  (didn't inspect the first reman guts) It was barely scored, bearings still looked good, nearly new.  It was clear that the bearings only had wear because the nut came off and allowed the thrust change, wobbling around and such.  Everything looked nearly new except the thrust bearing pieces had significant wear.  The radial bearings (brass bushes with holes in them really) looked fine but measured as too loose.

Share this post


Link to post
Share on other sites

Wow that’s nuts.

 

With each instance are the nut and shaft it threads to new?

 

What isn’t replaced when they rebuild it and could that part be compromised in some way?

Edited by idosubaru

Share this post


Link to post
Share on other sites

Loose impeller nut fact sheet

http://www.btnturbo.com/assets/factsheet_8_looseImpeller.pdf

 

I did not read anything about the oil being changed.

Seems like debris in the oil from the first failed turbo may have destroyed the 2 new ones.

(you mentioned loose bearings on #1 replacement)

 

Another website specificaly mentions Subaru and insists that you remove and clean the oil supply lines

to ensure adequate flow.before installing a new turbo.

Oil pickup screen too..

Edited by naru

Share this post


Link to post
Share on other sites

I have used several chras from what I'm going to assume is the same European company. I've never had an issue with their complete chra. From where I'm sitting this seems to be an assembly error, not a product quality problem.

Share this post


Link to post
Share on other sites

I thought the nuts to a CHRA shaft were supposed to be opposite thread to the direction of the rotation? I know lawnmower blades tighten in opposite direction to rotation for this reason (less you have a 2 pound machete getting launched). Are they using a correct thread direction for the application??

 

One thing though, is you can't just retighten the shaft nut. Everything needs aligned to the point of where it was balanced. So if the compressor wheel is advanced/retarded in relation to the rest of the shaft (think 1 o'clock vs. 4 o'clock) and retightened, it'll be out of balance, though I suspect your shaft probably bent and can't be reused.

 

I had good luck with a company called "g pop performance turbos" http://gpopshop.com/ You might wanna call them and see if they can help (real people answer the phone there). They have high-end balancing and can work with just the CHRA assembly vs. entire turbo to save on shipping. Prices are reasonable.

Share this post


Link to post
Share on other sites

Why would oil supply cause the nut to loosen?

 

If that were likely wouldn’t this happen far more often?

 

I get theoretically it changes fluid dynamics and forces on the assembly but causing the nut to back off on its own just seems unlikely or again it would be more common.

Share this post


Link to post
Share on other sites

I thought the nuts to a CHRA shaft were supposed to be opposite thread to the direction of the rotation? 

 

That keeps the nut tight against boost pressure,but,if the shaft binds for microseconds at a time,it tends to loosen.

Share this post


Link to post
Share on other sites

idosubaru, on 10 Feb 2018 - 09:43, said:

Why would oil supply cause the nut to loosen?

 

If that were likely wouldn’t this happen far more often?

 

I get theoretically it changes fluid dynamics and forces on the assembly but causing the nut to back off on its own just seems unlikely or again it would be more common.

 

Poor oil supply or worn bearings lead to microbinding of the shaft.

Shaft decelerates for a microsecond-interia of the compressor wheel and intake air wants to loosen the nut.

 

It does happen pretty often according to the turbo builders and a quick look around the forums.

 

Here is another reputable reference to "compressor nut missing"

https://www.ms-motorservice.com/fileadmin/media/MAM/PDF_Assets/Turbocharger-damage-in-PSA-Motors_54369.pdf

Good info on measuring oil flow too.

Edited by naru

Share this post


Link to post
Share on other sites

Loose impeller nut fact sheet

http://www.btnturbo.com/assets/factsheet_8_looseImpeller.pdf

 

I did not read anything about the oil being changed.

Seems like debris in the oil from the first failed turbo may have destroyed the 2 new ones.

(you mentioned loose bearings on #1 replacement)

 

Another website specificaly mentions Subaru and insists that you remove and clean the oil supply lines

to ensure adequate flow.before installing a new turbo.

Oil pickup screen too..

 

We did put new oil in and verified the oil supply through the lines.  And note when I said loose, I mean just barely, and in a wedge pattern......meaning they wore because the vanes of the impeller where pushing against the housing after loss of the nut, which puts a side load on the radial bearings and a major angled force on the thrust bearing, which showed the most wear.......Even still........we are talking about tiny scratches not chewed up, ground away metal like your pics......If we hadn't measured the ID of radial bearings, you might not know they were worn at all.  Only the thrust bearing plate (with the tiny feed hole) showed real sign of "grinding"

 

Since I posted yesterday we went ahead and removed the oil pan.  No "debris" to be found.  There was a bit of sludgy stuff in the bottom of the pan, but nothing metallic, and like I said, there had been oil flow to the turbo.

 

I removed the oil cooler also, this car has a "double stack" assembly that actually points the oil filter back away from the exhaust.  4 O-rings to seal it....geez.  Gonna clean that and replace the oil pickup tube o-ring as well.  No signs of trouble with it though.

 

Didn't cut open the filter yet, but I will later today and see what that reveals.  I would LOVE to find something that takes away the mystery, even if it's bad news.....but right now it's still a head scratcher.

Share this post


Link to post
Share on other sites

Poor oil supply or worn bearings lead to microbinding of the shaft.

Shaft decelerates for a microsecond-interia of the compressor wheel and intake air wants to loosen the nut.

 

It does happen pretty often according to the turbo builders and a quick look around the forums.

 

Here is another reputable reference to "compressor nut missing"

https://www.ms-motorservice.com/fileadmin/media/MAM/PDF_Assets/Turbocharger-damage-in-PSA-Motors_54369.pdf

Good info on measuring oil flow too.

 

 

Hmmm.... the way I read this article, it is listing a loose or missing compressor nut as a CAUSE of oil starvation to the bearing...

 

From the link  

"Damage symptoms and causes

 

—Rotor shaft is jammed or blocked

Cause: Inadequte oil supply due to the shaft bearing obstructing the oil system (ill 3.)

— Shaft nut loose or removed on compressor side.

Cause: Delays, i.e. blocked rotor shaft.

Result: Shaft nut leaves impact marks in the funnel of the compressor casing or on the compressor wheel........"

 

 

Kinduv a Chicken or Egg scenario, but the way I am reading this......an incorrect bearing, or an incorrectly installed bearing could have blocked the oil supply (since I've verified oil supply to the unit) and caused the shaft to stall.

 

And THEN that caused the shaft to bind kicking the nut off

 

The reason I am so strongly feeling that the problem is in the turbos is that the nut failures were so sudden.  Very little wear on the bearings or shafts at all.  Not compared to the OE unit which was ground to hell, but still had the shaft nut tightly in place.  Both replacements tossed that nut with hardly any wear showing on the shaft, in a matter of minutes. Seriously less than 2-3 mins of driving either time.

Share this post


Link to post
Share on other sites


Out of curiousity, were both turbos dry of oil at start up? i.e. you got them back from the rebuilder, installed back on the car (manifold, oil and coolant), and engine started? Or did you add oil directly to the turbo via the oil feed, hand turn, etc. until sure it was fully primed before reconnecting and starting the engine?

Share this post


Link to post
Share on other sites

 

Out of curiousity, were both turbos dry of oil at start up? i.e. you got them back from the rebuilder, installed back on the car (manifold, oil and coolant), and engine started? Or did you add oil directly to the turbo via the oil feed, hand turn, etc. until sure it was fully primed before reconnecting and starting the engine?

 

First one I installed without pouring anything in the oil feed first.  But I did leave the Banjo bolt cracked and cranked engine without starting until oil flowed out to verify oil to the unit.  Then tightened it down and started.

 

Second one I poured oil down the feed hole until it began pouring out of the drain line.  Then installed and checked for flow to the unit again before starting.

Share this post


Link to post
Share on other sites

Those were rapid demises indeed.

It does make one wonder.

 

The way I read it there are 2 poor lubrication/loose nut scenarios.

 

In the first,poor lubrication causes bearing wear allowing the turbine wheel to hit the housing thereby slowing the shaft and loosening the nut.

 

In the second,poor lubrication or debris slows the shaft of a tight or normal bearing and the nut loosens.

 

Here is a Honda story that sounds eerily similar to yours

https://honda-tech.com/forums/forced-induction-16/compressor-wheel-nut-keeps-coming-off-2506930/

2 loose impellor nuts within 25 miles.

Restricted oil line.

 

I agree that a bearing fitted too tightly COULD be the problem.

 

I would want a seperate oil pressure gauge  on the turbo fitting for the next test run just in case.

 

Don`t know if you read the other links,but,the first insists that shaft binding is the ONLY reason for loose nuts.

Share this post


Link to post
Share on other sites

When I had a turbo rebuilt for my Saab years ago, I pulled the hard lines (it had banjo bolts as well) and sprayed the lines, banjos, and bolts with oven cleaner and eventually chased with garden hose high pressure setting. After several cleanings/rinses, everything was back to bare metal. Also, the water flow (or lack thereof) can indicate if sludging in the lines is present. Also worth checking if the drain line is getting plugged as it enters the pan, or conversly the oil feed is lacking. If you have an oil pressure gauge laying around (or just buy a $20 pod gauge at parts store) consider unhooking and unbolting the turbo (run open exhaust) plugging the return line, looping/plugging coolant lines, and thread the gauge into the oil feed for the turbo. My NA ej22 with 10w30 is usually 75-80 psi cold idle, and around 10-12 psi fully warmed up @idle, and suspect yours should be around those numbers if all is well. If extremely low and no oil restrictors, you might have an oil pressure issues within the engine itself that needs clearing.

Share this post


Link to post
Share on other sites

That's a head scratcher, for sure. Keep us posted!
 
 
I know the conversation has moved on, but I hate this kind of mis-information. I know a lot of people prefer to remove those screens, and that's fine. But it is NOT directly from Subaru. In fact, if you buy a Turbo from Subaru, it will not be warrantied unless you replace the turbo feed screen.
 

Though there is a TSB about removing the screens in all the banjo bolts. Both AVLS solenoids, as well as the turbo one (I think)

 
 

REMOVE THE BANJO BOLT SCREEN!  There is a TIB for this.

 

Attached is the real Subaru TSB

Banjo Bolt.pdf

Share this post


Link to post
Share on other sites

Ok, so just the solenoids require the removal of the mesh screen. Not the turbo feed.

I guess I just bought the new feed banjo from subaru and didn't even think to look for the screen.

Share this post


Link to post
Share on other sites

Ok, so just the solenoids require the removal of the mesh screen. Not the turbo feed.

I guess I just bought the new feed banjo from subaru and didn't even think to look for the screen.

 

On this 04 the Turbo feed line and the AVCS use the same port on the back of the pass head.

 

Didn't replace the screen, but I did verify that it is clear and flowing.

Share this post


Link to post
Share on other sites

Numbchux, you appear to be correct.  HOWEVER.  EA81T/EA82T/EJ22T/EJ20G//EJ205 all came without the screen.

 

You don't need the screen, nor should it have ever really been spec'ed by FHI.

Edited by carfreak85

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×