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Discussion Starter · #1 ·
Alright guys, this is an issue I've never encountered before. I have always had an incredibly noise engine (purchased the car with 182k miles), and figgured it was the timing chain. I planned to do a complete overhaul of my NG900 once I get my C900 running, and classes are over; but the NG900 got jealous of all the attention the C900 was getting and she has other plans, this what happened.

I drive the **** out of my car, and the other day I was bounching it off rev limiter in first, and when I came down to idle, my timing rattle became very loud. At anything over 2500 RPM's, it sounds like something is bounching around in my engine.

I pulled the valve cover, and my timing chain is a bit loose, but not enough to make this sound, nothing out of the ordinary. I am losing no oil, no collant, nothing, so I'm going to rule out ring landings, and it is a slapping sound, so I'm going to rule out bearings.

What does a bad balance chain sound like, and how do I fix it! I hear people just cutting the chain with the oil pan off, is that a good idea? Should I install Genuine Saab's Balance Shaft Delete Kit? What's the deal guys!

Tom
 

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Mine was removed while the oil pan was off (for cleaning). The mechanic cut it from the bottom, removed the chain and left everything else in place.

However that does not completely address your other symptoms, because with that much noise, you may have sheared a few teeth off the balance chain sprockets, and metal particles may be in the oil pan, the oil pump, and so on.

The end of one of the plastic timing chain guides might have broken, which is not something you can tell by checking the timing chain tension from the top, etc... If something that broke IS bouncing around under the timing cover, it will be an engine-out job.

Probably the first thing that should be done is inspecting the timing chain tensioner, with valve cover in place. That tells you where you stand with the timing chain. The position of the tensioner reflects the excess play in the whole timing chain system, incl. the guides. Pulling up on the chain from the top does not do that. After that, clean any metal bits out of the oil pan, and on from there.
 

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Discussion Starter · #4 ·
Thanks PMI, always been the most thorough guy on the board. If no one has said it, we missed you and your information terribly. It's good to have you back!

I do need a new chain and guides (they are a tad worn and the tensioner is almost fully extended), however I plan to do a FULL rebuild after class is over (in four weeks). So should I even bother to roll in a new chain (one with a master link) and remove the balance chain, or just do the balance chain and do the timing chain when I do the full engine overhaul....
 

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genuine saab sells a tensioner blockoff kit. your slap sound could be piston slap. you could have spun main bearings, i don't recommend just cutting the balance chain. pull the motor do it the right way, pull the chain and tensioner and install the oil passage block off leave the shafts in, i took the balance chain guides out and replaced the spots with washers but you can leave the guides in. the timing chain should not be loose. it is automatically tensioned with a spring tensioner located on the back side of the head
 

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Discussion Starter · #6 ·
I unfortunately don't have time to do it the best way AZ, I live an hour away from school and I've got 4 weeks left. I guess I'll try to remove the balance chains, and drive it till I can be done with school and do a full rebuild with engine out. I don't know how I would have piston slap (internals are stock and never been change, not like they installed a piston backwards from the factory) and I've pulled the head before and valves were fine and pistons were fine. I suppose bearings are possible, however they will be changed and I'm always good about oil changes and checking oil level (we all know that the stock rev limiter is far lower than any damage causing high revs). I hope pulling pan will show some balance shaft teeth, and when I pull the chain all will be well, but things that lucky tend to not happen to me.

Tom
 

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... So should I even bother to roll in a new chain (one with a master link) and remove the balance chain, or just do the balance chain and do the timing chain when I do the full engine overhaul....
Since you already know that the tensioner is NOT fully extended, I would leave that alone for now. As long as there are any clicks left, rolling in a new chain from the top will not help in the short run. Most of the excess play will be in the guides anyway, not in the chain. You can inspect the teeth on the timing gears from the top, and to some extent on the crank gear from the bottom.

I think you do have to get the oil pan off to see what might be inside. If you know how, you should also inspect at least one of the main bearings, and one of the rod bearings, mine were in pretty sad shape by the time we got to them.

Cutting the balance chain would depend on what you find, personally I am happy to be rid of mine, but not everyone feels the same way about that.

And, thanks, :)
 

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atcutally i spun my main bearings bouncing rev limiter. piston slap (edit) SOMETIMES cannot be seen by removing the head, nor is it just because of upgraded internals. it can be caused by worn cyl whether at top or bottom, causing piston slop

I unfortunately don't have time to do it the best way AZ, I live an hour away from school and I've got 4 weeks left. I guess I'll try to remove the balance chains, and drive it till I can be done with school and do a full rebuild with engine out. I don't know how I would have piston slap (internals are stock and never been change, not like they installed a piston backwards from the factory) and I've pulled the head before and valves were fine and pistons were fine. I suppose bearings are possible, however they will be changed and I'm always good about oil changes and checking oil level (we all know that the stock rev limiter is far lower than any damage causing high revs). I hope pulling pan will show some balance shaft teeth, and when I pull the chain all will be well, but things that lucky tend to not happen to me.

Tom
 

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Discussion Starter · #9 ·
Alright, I suppose it's possible that I could have spun my bearings. If this is possible, what damage do I cause while continuing to run the car, score the crankshaft? Can I swap bearings with the engine in the car? Ugh I need to do a full engine rebuild, but I dont have the time till another month. If it is bearings, will I do any damage running the car for 4 weeks on bad bearings? I suppose piston slap is possible as well, I did run 12psi of boost on my N/A 2.3 motor for about 3 months, it was a tad unhappy.

Tom :evil:
 

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Can I swap bearings with the engine in the car?
Yes, from the bottom. That's how it was done on my car, but the car was on the lift. Not sure I would want to do it without one, I have a low tolerance for getting oily crud on my face, and you have to exercise a modicum of care, since this is one area where reassembling something with the wrong torque can really hurt you.

If it is bearings, will I do any damage running the car for 4 weeks on bad bearings?
That's a crap shoot. When the rod bearings start to seize, a rod will usually fail, and come out through the side of the engine. Hard to say how often that happens. Until you take a look, we are just guessing what might be wrong.

I think I came pretty close. On this car, the rod bearings are apparently more fragile than the mains. This was the worst one of the lot, the mechanic laughed and told me he had never seen one in pieces like this from a car that drove in under its own power.

 

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Discussion Starter · #11 ·
Hmm, I'm pretty good with being oily and whatnot, actually I perfer it! Anyway, to get at the rod bearins, I'm guessing one would have to drop the crankshaft. Does anyone have a procedure or DIY of doing this through the bottom end, with engine in? That would be great!

Thanks,
Tom
 

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I am pretty sure the crankshaft stayed where it is, but it was a few years ago. I was more interested in how the bearings looked at the time.

I was sort-of trying to make a joke about the oil, seems like a job that would be difficult with ramps or stands. I would ask for some tips in the C900 forum, I suspect there are lots of people there who are intimately familiar with both sets of bearings.
 
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