See above.
What could cause the securing nut to fall off the compressor impellor of a brand new / Subaru supplied / standard turbo charger? The unit has done less than 200 miles.
If the turbo suffered poor oil supply and seized, would you expect this nut to unscrew itself? I'm not convinced.
Thanks for any ideas.

 

wow that sounds unlikely the compressor nuts a left hand thread i believe to avoid it working loose ?? can someone confirm this,what turbo is this ?

 

Standard TD035. Same as installed when car built.

 

There's no such animal as a "TD035". There's a TF035, as fitted to the Forester, and there's the TD04, as used on the Impreza.

I can't easily see a circumstance under which a 200 mile old turbo could seize either - with the possible exception of the oil supply being completely blocked. Even if it happened, again I can't see a mechanism by which it'd undo the compressor nut.

And, as above, the compressor nut is left-hand threaded, and so should never work loose in use provided it has been properly installed and torqued. As such, the implication here is that the turbo was not properly assembled. If it's as new as you're suggesting, the obvious recourse is straight back to the supplier.

 

thankyou splitpin for confirming that its lh thread

 

Thanks for replies. I'm not having much luck at the mo. Its a Forester so must be the TF035 LOL.
I had a new Subaru turbo fitted about 2 months ago which lasted a couple of weeks. The compressor impellor was damaged by foreign material (source unknown but not off car. Legal case pending with garage). The next unit fitted and supplied by Subaru last week, as I've been awaiting delivery for a month. Just checked with inspection camera through intake and the securing nut has come off! Whats going on?
Oh, and oil pressure checked by Subaru. Found to be ok to Turbo.

 

It sounds, on the face of it, that you literally have been unlucky, as far as the second one is concerned, at least.

In the case of the first failure, about the only way "foreign material" can get into the turbo is if something further up the inlet tract breaks off (there aren't exactly many things that could do that, and if something like this had happened, the broken part would be visible) or, as would appear more likely in your case, some clumsy spanner jockey has left something in there when the unit was fitted.

In the case of the second one, it's difficult to theorise without actually having the unit on the bench in front of you (normally, when you can see it, the failure process tends to be quite obvious), but as above, it's difficult to suggest anything much other than that you've got the one that slipped through the quality control process.

 

Yes split pin, my thoughts exactly regards the first failure. The second failure has me scratching my head. I can't believe how unlucky I have been.

 

Could a faulty / stuck blow off valve cause enough back pressure to cause turbo stall, enough to spin turbo in wrong direction? Is this even possible whilst engine is running, and if so, what symptoms would be experienced?

 

No, is the short answer. There is no mechanism by which the dumpvalve can cause backpressure. All it does is effectively make a hole in the inlet tract - thereby relieving pressure from it.

If you meant the wastegate, there's no mechanism by which one of those failing/breaking could cause back pressure either, all you would get is no boost if the wastegate sticks open. There is pretty much no concievable way you could get a turbocharger to spin backwards once installed.

Edited to add - having seen the other thread you started, it seems you're misusing the term "back pressure" (this term refers specifically to the exhaust side of an engine, not the intake), but I sortof get what you're trying to ask. The answer's the same though. First of all there is no obvious way by which a dumpvalve (especially an OEM Subaru one) will jam shut. When they fail they almost invariably open too much (because of a fractured or de-tensioned spring) rather than the opposite.

Secondly, if you did do something that jammed the dumpvalve shut (or deleted it), you certainly would experience compressor stall. However, again, you still wouldn't end up spinning it backward, and, if there was any effect on the compressor nut as a result of something like this, it would be further tightened, not loosened.

 

Was this second turbo a completely new unit (did you see it?) or could it be a rebuild of the first failure?

 

Brand new unit Butty, the old one is in my garage lol (dont know why I'm laughing there, must be the drugs kicking in). The first unit was not fitted by Subaru. To be fair Subaru have been as good as gold, think I am sorted now. Hopefully this will be the last of the problem, fingers crossed.