broken turbo

That's like asking "what happens when the brakes break, is it like having no brakes at all, or do you have some braking?".

As will all complex systems, there are many, many failure modes, and the resulting symptoms will depend on the failure mode. There aren't many turbo failure modes which result in total engine failure, but there are some.

Usually the turbo doesn't fail at all. If it does, a common mode is that the bearings start getting noisy, and you get a loud whine from it while using it heavily. If you wait long enough, the impellors will eventually start hitting the insides of the housing, which turns the whine into a howl. This, of course, wears on the impellors and housing, making a rebuild of that turbo less of an option , because the parts aren't in prime condition.

Is this a curiousity kind of question, or are you having problems with a turbo? Maybe with more details in the question a better answer could be given.

Dave Hinz

If the turbo bearings go, then oil might spray into the air intake of the engine proper and clouds of blue would result?

I don't know; I've never had one of mine misbehave. The two turbos I've had apart belonged to others, and I don't know the smoke history of the car. It's been years, so I can't visualize how specifically the seals relate to the bearings, but I _think_ that that would be a different failure mode. The bearings are pretty much designed to let oil float all around them, so they don't block it from getting anywhere. The seals are further towards the airflow sides of the turbo. I've heard of those failing too, which would probably be the "smoke" mode of failure, as opposed to the "whine" or "howl" modes caused by bearings.

Is there anyone here who has seen a meaningful number of failed turbochargers on Saabs who could comment? I don't think any individual will have seen many, if any, failures.

Dave

Any one of a number of things happen, but the usual cause is worn bearings or failed oil seals. If the bearings wear you need to rebuild the turbo before the housings and impellers are damaged from rubbing, if the oil seals fail you'll have massive oil consumption, lots of blue smoke, and it can plug up the catalytic converter. Either way it's something that needs to be fixed immediatly.

Also at least in the Volvo group people occasionally ask if they can just remove the turbo, the short answer is no, if the engine runs at all it'll run like crap and won't have nearly the power of the standard non-turbo engine.