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#1: 10-30-2011, 05:54 AM
Turbo failure wiki
 
 fahr_side
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Blown turbo info roundup thread.

Every other day a new thread is started along the lines of ‘OMG my stock turbo died, what should I do / what went wrong?’ etc. This thread will try and answer all these questions in one place and others related to it as they come up. Hopefully it will snowball into enough info to warrant a link or mention in the sub-forum FAQ. Please feel free to add questions or answers or offer better information if you have it.


Which cars are affected?

All 2.5 liter turbo models with OEM single-scroll IHI turbos are seen to suffer these failures. That means 2005~2009 LGT and OXT models to those in North America. Twin-scroll models sold in other markets do not seem prone to these problems. 2007 and later models with the revised VF-46 also seem to less effected, though it’s possible less failures are seen because there are less on the road or if they have just covered less miles so the failures haven’t started yet.


Is there a recall?


There has not been a recall on the turbo, oil supply system or related hardware. Some TSBs including this one have been released which discuss the issues with banjo filters etc., OCI has been reduced since the car was launched and Subaru themselves stopped fitting the banjo filters to several models in 2008.

Can I claim it on warranty?

Varying success on this. Some have been denied. Some have had a turbo replaced. Others have had their parts provided on warranty but had to pay labor themselves. Some have had a turbo but after the engine failed were on their own. Some have had both engine and turbo replaced / overhauled on warranty. Subaru are obviously aware of the issue at some level but not every dealer is. You may want to call in an area service writer to assist. As in all powertrain warranty claims, Subaru will likely deny you cover if you have done power mods like a downpipe, intake or stage tune. Proceed with caution. YMMV.

How many fail?

Check out the very helpful survey thread. From anecdotal evidence it seems a lot, though people who go 100k without failure don’t complain about it and are less likely to post this information. Many people go to very high mileage on the stock turbo, though this is of no comfort to those whose turbos fail.
Your turbo is not guaranteed to fail. Nor is it guaranteed to go forever. A journal-bearing turbocharger is to some extent a wear item like any other on your car. How it lasts depends partly on it's design, build quality and application, and partly on how you use and maintain it.

What will happen?

Symptoms of failure.

  1. Smoke. Some owners see smoke from the exhaust before or during failure, typically there is more smoke while in boost. May or may not be accompanied by oil in the intercooler, noticeable oil consumption.
  2. Noise. Owners report squealing, screaming noises from under the hood much of the time. In some cases it’s instant failure with no warning but most seem to be able to limp some distance before complete failure.
  3. Metallic particles in the oil. Very often very fine and non-magnetic, so magnetic drain plugs or magnets stuck on the oil pan may not catch this.
  4. Catastrophic turbo failure, no boost, CEL etc. Many owners report being stranded at the roadside unable to start or run the car. Very often it’s possible to run the car very gently but no boost can be obtained.
  5. Engine lubrication failure, oil contamination, catastrophic engine damage. Some owners have continued to run the car past the point where the turbo failed in order to get home or to a shop, and had the engine fail completely on the way. Usually a bearing spins, the oil pressure light comes on or some other combination of CELs occurs and the engine will no longer run or is so noisy the owner won’t run it any further.

Consequences

  1. Turbo failure. Problems usually start with oil leaking into either or both the turbine and compressor housings. A leak on the exhaust side will manifest itself as a smoky exhaust and turbo wear can be confirmed by pulling the downpipe and checking for radial play on the turbine wheel. If the problem isn’t solved at this point either the bearings wear so badly that the wheels crash the housings so hard they won’t turn any longer, or the shaft itself breaks right behind the turbine wheel.
  2. Oil contamination. The failing turbo bearings produce a stream of fine particles of bearing metal and / or the turbine shaft itself introduces steel particles in the oil draining from the turbo back into the oil pan. Obviously the longer the engine is run after the symptoms begin, the more contamination will be created.
  3. Possible engine bearing failure. Oil from the pan is of course picked up by the oil pump and passed through the filter before it’s returned to the main galleries. However, oil filters do clog when overloaded with suspended particles and they have a bypass to prevent blockage from stopping the supply of oil to the galleries. Better to have dirty oil circulating than none at all. The fine particles can and will clog the oil passageways in the engine, and score bearings from mains and rod ends to camshafts. Given enough particles and time the whole engine can be rendered damaged to a point where all moving parts need replacement. The camshafts run directly in the cylinder heads with no metal bearings. Wear on the camshafts can and will damage the bearing surfaces badly enough to render the heads useless.
  4. Possible engine failure due to ingestion of compressor debris. Not sure if this has been documented but potential exists for parts of the compressor wheel to get into the cylinders.

Underlying causes

  1. Oil change interval. Subaru now recommends an OCI of 3,750 miles for all turbo models and insists on synthetic. Back in 2005 the OCI was 5,000 miles and dino oil was okay. Perhaps Subaru has increased the requirements due to all the turbo failures. Many long-term owners prefer to change oil at 3,000 miles.
  2. Oil quality. We can debate all we like on what oil is better but as long the lube meets Subaru’s specs and is changed at the recommended interval it should be sufficient.
  3. Oil filter screen in oil delivery pipe aka banjo filter. On 2005~2008 models here is a small mesh screen filter hidden away in one of the banjo fittings which supply oil to the turbo. Note that the oil supply comes out of the passenger (LHD) head oil gallery, which also supplies oil pressure to the AVCS solenoid. It is filtered oil and as such should be as clean as it gets. It seems reasonable to surmise that Subaru initially fitting a filter means there are good chances that contaminants will make it past (or around) the main oil filter. It could be they expect owners will miss an oil change or extend it so far the filter becomes clogged and bypassed. The stock banjo filter is very small in size and can easily become so clogged with debris it starves the turbo of oil. The location of the filter is so well hidden that many Subaru techs are unaware of its existence.
  4. Weak turbo design. The turbine shaft is extremely small in diameter and there is a groove cut into it right behind where the turbine wheel is welded to the shaft, which is believed to weaken it considerably. If the shaft breaks, this is where it will happen. IHI’s bearing design is considered by many to be rather outdated, and inferior to other, newer designs. IHI themselves have several different bearing cartridges and they vary in size. The VF-40 and VF-46 use some of the smallest cartridges seen on turbos with wheels in this size range. It may be noted that ’08 WRX and ‘08~ FXT models are fitted with MHI TD04 turbos and run similar boost pressures as the LGT / OBX. Very few turbo failures have been reported on these cars.
  5. Tuning. It’s hard to tell from anecdotal evidence what percentages of failures occur on tuned cars and whether or not cause and effect can be proven. Stock boost pressure is in the range of 1 bar. Stage 1 and 2 tunes can push boost pressure up to 17psi or even higher. In order to reach these pressure ratios the turbo has to spin faster, all other factors being the same. It’s understandable that the bearings should require more oil to retain a hydrodynamic wedge at increased speeds as radial loads to the wheels increases. If the oil supply is already limited, it is reasonable that more failures could occur when running at higher than stock boost.

Immediate remedy

Replacement turbo. VF-40 and VF-46 turbos are available from Subaru dealers and the usual online genuine parts vendors. IHI turbos cannot be practically be rebuilt as genuine overhaul parts like replacement turbines, compressor wheels, bearing kits, seals etc are not generally available. While there are kits out on eBay there isn't any info on how well that worked out. Even though you can buy parts it's not possible to DIY a turbo overhaul as the wheels needs to be balanced to extremely high specifications since the assembled compressor and turbine spin at such high rpms.
The only practical repair is to purchase a complete center housing rotating assembly (CHRA) and fit your housings to that. Of course if your housings were badly damaged when the turbo failed this is not going to work for you.

Several vendors now offer direct bolt-up replacements (upgrades) for turbos with the vertical compressor outlet unique to later LGT, OXT, WRX and FXT models. A list of suppliers appears in Appendix I below. While STi / early WRX-style turbos can be fitted directly to LGT models, this falls beyond the scope of this article.
Please note that replacing a turbo does not guarantee your problems are over. A second turbo failing shortly after the first is quite common.


Preventative measures before failure. Not every turbo fails but there are some points worth noting if you want to be the one to brag that you’re at 200,000 miles and still on the original turbo.

  1. Oil change interval and quality. Stick to the recommended OCI or have your oil analyzed if you think it might need changing more often. Use synthetic oil with the specifications that Subaru requires. There are many threads dealing with the question of which oil to use, all of which can be found via the search function. Definitely check your oil level regularly and keep it topped up.
  2. Banjo filter cleaning. You can remove, clean and replace the banjo filter every time you change your oil, or every two times or whatever makes you comfortable. Many people report having found debris on that filter even they thought their OCI was sufficient. Others have taken them out spotlessly clean. You could make sure it’s clean and sleep better at night.
  3. Banjo filter removal. There are two schools of thought about this issue, which can summarized as follows:
    • Pro-filter. Subaru put it there for a reason. Without the filter, dirty oil will contaminate the turbo bearings causing them to fail. If the filter is kept clean, there is no problem.
    • Anti-filter. If the filter is clogged, the turbo bearings will fail. It’s very hard to get to the filter and even Subaru techs often fail to find it. You might decide to follow Subaru’s lead and put more faith in the turbo being able to deal with contamination than your ability to keep up with the OCI or keep the engine topped up with clean oil. In this case you could pull the filter and toss it in the garbage.
  4. Oil line and / or filter upgrade. You may decide the stock oil supply isn’t enough or isn’t filtered well enough. Several kits are available that have bigger diameter lines. Some are filtered. More info in Appendix II below.
  5. Turbo replacement. Some people go so far as to replace their stock turbo with a different one in order to avoid all of these issues before they happen. Options in Appendix I below.

Preventative measures after failure. The turbo failing is very often not the end of the story. A great many people have suffered a second turbo failure shortly after the first and almost as many have reported an engine failure after the initial turbo dying. Chances are that if you have bearing particles in your oil you are going to have a bearing failure. You can try to prevent further problems with the following steps. Whether you take these steps or not you can still experience a second turbo or complete engine failure after the first, but it's cheaper and easier to try prevention than cure.

  1. Banjo inspection / cleaning / removal. If one turbo has failed it’s wise to look for the cause before installing another and just driving the car. You should at the minimum check the banjo filter is present and see if it’s dirty. A dirty filter is a sign that the turbo may have been running on a restricted supply of oil and failed from starvation. You may decide if you want to wash and replace it or ditch it or choose another oil supply solution altogether.
  2. Drain oil and check for contamination. A failed turbo bearing will probably leave contaminants in your oil. Left unchecked they will start to clog your oil filter and could pass either through or around it to cause more engine damage. Drain the oil and inspect it for bearing metal or steel leftovers from the turbine shaft.
  3. Pan inspection / cleaning. A really caring owner might want to drop the oil pan to see if there is any bearing material lurking in there, which didn’t drain out with the oil. Normally you’d expect if there is bearing metal in the oil, the pan is also contaminated. It's been reported that the shape of the oil pan is so complex and there are so many places for metal particles to get stuck, that it's really impossible to clean properly even with ultrasonic cleaning, and only replacement will guarantee no contamination re-enters the lubrication system.
  4. Engine flush. Whether the oil appears to be dirty or not, bearing debris can be present in the block and oil passages that didn’t drain out with the oil. A flush is a cheap way to help any such contamination to make it out of the engine.
  5. Oil cooler replacement. The oil cooler module which sits above the filter is reported to have such complex and narrow passages inside that contamination can easily build up inside and while impossible to clean properly, that contamination can escape slowly over time. You might have flushed the engine and cleaned the pan, but still have contaminants coming out of the oil cooler between oil changes. Only replacement will fix this, and it’s a $230 or so part here or here.
  6. Intercooler / intake manifold cleanup. If the compressor wheel has lost any vanes or parts of, take a look into the intercooler to see if they are loose in there. Nothing is likely to make it through the intercooler but better clean out any metal shards in there just in case. Anything that did make it through has either damaged something or not on it’s way into the exhaust. Either it did or it didn’t cause any damage.
  7. Debris in downpipe. If you have a catted exhaust there may be metal shards in front of the first one. Shake them out before reinstallation.
  8. Catted uppipe. Unrelated but well-documented issues with early cars having the cat in the uppipe come apart and destroy the turbine. While you have the turbo out for replacement, either gut the OEM pipe, fit a catless OEM pipe ('06~ WRX / '07~'09 LGT / any FXT or STi) or an aftermarket item. Note the stock cat is not ceramic and not as easy to hack out as the ones in the downpipes. Some owners have had a hard time removing it.
Appendices I and II appear below with info on repairs, rebuilds and replacement turbos and oil feed / filtration upgrades.

Last edited by fahr_side; 06-28-2013 at 09:27 PM.. Reason: Moar info
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