[jmkcc]

My turbo went a few weeks ago. Felt a pop, then a scraping noise coming from belt area and then a smoke show started. I had just left work and limped back to the parking lot. Started to hear a knock and shut her down until I could tow it home.

The engine always had a slightly off sound, a feint rumble at certain rpms which I could never trace but thought was balance shaft bearings. Oil pressure was acceptable but on the low end. I had previously replaced main and rod bearings which were not bad at all but I was already committed.

When I did the bearings I found a 1/8" strip of metal about 3/4" long that had a slight curve to it. The metal kind of resembled a bearing but the diameter was way to small to be any of the engine's bearings. I could not figure out where it could have come from and hoped PO had dropped something in the sump and the magnetic plug caught it before it could do much damage.

I pulled the engine then the head and the timing chain cover last week to grab the new chain and guides. When I pulled the timing cover a similar but longer 1/8" strip of metal fell out. Then I noticed that the balance chain sprocket had "separated" - the backing that is stamped or welded to the sprocket was hanging on the mounting spindle and one of the metal rings or spacers that are on either side of the sprocket was missing (the unidentified bits of metal I had found!). There was a good deal of slop in the idler sprocket and the exhaust balance shaft sprocket had a noticeable bend in it's outer plate or cover so one of the pieces must have ground through that sprocket.

I'm guessing that was the source of the rumble. I had installed a new timing chain kit - but I cannot recall if it included a new idler sprocket or not. Kicking myself for not noticing any defect in the idler during the install.

It's the old chicken or the egg conundrum, what came first - balance chain failure or turbo failure. Either way the result was catastrophic. One piston is loose in it's cylinder (can be rocked back and forth) and I have not had time to pull it to see what's up with that. The cylinder does not appear scored which is weird, so maybe the quick shutdown saved the block.

I'll try to post some pics this week. Seems like a strange part to fail. I'm kicking myself for not deleting the balance chain when I did the timing. I've done the delete on a 900 and 93 but got nervous about some of the posts on deleting the balance shafts on a 2.3. However, I'm going for the delete on the engine that's going in next. I'll post the results of that at some point in the future.

So a bit of advice when doing a timing chain - check the balance chain idler sprocket carefully!

 

[Jeremy R.]

Good advice! I bought a 9-5 Aero with engine problems, and the cause of its problems was the balance shafts. They had seized up from sludge, which caused the balance chain to strip all of the teeth off of the balance shaft sprockets, and then the balance chain had enough slack that it was starting to wear through the oil pickup in the timing cover. It was a lot of work and way too much money to get that engine running again, but I did it. I had heard the same stories about too much vibration when deleting the balance shafts on a 2.3. I was initially going to do it, but when it became obvious that this was going to be my wife's kid-hauling car for a while, I decided to leave the balance shafts, although they were scored enough that I used some spare ones I had in a B234 block out of a 9000.

 

[jvanabra]

*sigh* I remember the days when your Saab left you on the side of the road and you could always say, "At least it's not the engine."

 

[Tboy]

Looking forward to pictures.


Nick at GS had always been against balance shaft deletion on the 2.3. I remember having that conversation with him long ago. I don't know if that has softened in recent years, I know there are lots of people who have done it. I understand your concern, and position now, it's just one less thing to fail, and might not be considered "required". Still, I would assume that failure is pretty rare.

 

[mio]

Nick at GS had always been against balance shaft deletion on the 2.3. I remember having that conversation with him long ago. I don't know if that has softened in recent years,

His viewpoint on this issue has not changed. GS recently completed a Viggen engine build for me and the balance shafts were retained.

-Mike

 

[EdT]

I wonder why some balance or timing chains go, while others don't.


As far as I know, there was never any work done on the timing or balance chains/guides on my non-turbo 2.3. They all worked fine for 392,000 km. (And in fact I have never checked the tensioner extension.)


Not only that, the gearing is shorter on the non-turbos, so 100 km/h is pretty close to 2500 RPM. That engine spent many episodes of a few hours at continuous 3000+ RPM on the highway.

 

[jvanabra]

I have heard from several mechanics that the non-turbo 2.3 was subject to timing chain problems, but I've never heard any technical breakdown.

Jeremy's problem may be the poster child for this failure - sludge -> low oil pressure and/or buildup -> balance shaft failure. If true, it would certainly follow that turbos would be more susceptible to the issue.