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Hi,

So in order to spend all the spare time I have, I did some work on my 9k CS 2.3T (-92), now at about 240000km's. Among other things, I opened the cylinder head and timing cover. I know there is stories going around about balancing shaft problems on the Saab 9000. Well, I guess there is some truth in it...According to the info I have, the early (1990-1992) B234 (2.3litre) engines have too weak drive sprockets for the balancing shafts. So if you have that model year, check the condition of the balancing shaft system asap...Needless to say, I threw the chain away, and the engine sounds MUCH nicer and I did not notice any increase in vibrations after disabling the balancing shafts.



-Ville
 

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The word is the sprockets on early balance shaft engines were not hardened correctly. Your picture shows that clearly. Anyone going that deep into their engine would be wise to replace the chain and sprockets. Of course, the balance shaft is primarily for cosmetic reasons, less noticeable vibration from the engine. The engine should run fine without them, though it will tend to throw up some interesting vibrations at certain sustained rpm.

There's no magic to balance shafts, the older smaller four cylinder has the same vibration pattern as the bigger ones it is just that big fours tend to develop big enough vibrations as to be objectionable to many customers. Not all big fours have balance shafts, the superb BMW M3 engine which eventually went to 3.0 liters didn't use them as far as I know. SAAB has adopted balance shafts even for their smaller four now and I believe many other manufacturers have also.
No question balance shafts make for smooth running (some V6 engines also use them) but its no free ride. The balance shafts do absorb some torque and add to the rotating inertia of the crank.
 

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What was the warning about oil flow and oil galleys? I can't quite recall and can't find the info. Besides vibration, are there any other drawbacks to disconnecting the mechanism?
 

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That definitely looks like a well worn timing chain sprocket. How long and how hard was it to gain the access to the lower sprocket? Did you pull the engine or were you able to get enough room while the engine was in the car?I keep contemplating changing my timing chain and sprockets on my NG900's B234i engine, but don't have the time or means to take the engine out.

When I got two FOBs programmed at the stealership (my only visit), I asked the mechanic about the timing chain and he told me to not worry about the timing chain.....because I should be more worried about the balancing shaft chain.
 

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No need to take the engine out, there's plenty of room. You go in through the inner wheel arch, remove all the moving gubbins, then take off the timing cover and there it is! :)

Always a good time to also change the head gasket as there aren't that many more bolts and oh, while you're there, get the alternator checked, particularly brushes and change all the water and oil O rings, both idler pulleys, front crank oil seal and stick on a nice new belt at the same time.

Set you up for another 100k miles.

Timing chain or balance shaft chain, in my opinion, you have to remove the cover to inspect it all. It simply isn't enough to remove the cam cover and look at the cam sprokets as many seem to want to. As the Saab mechanic said, it's the balance chain and there are 5 more sprokets that can't be seen without the cover off.

David.
 

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i am curantly altering a B204 9000 engine to fit in to a 9-5, i have 2 to choose from but both had the ballance shaft sprockets worn down to nothing but the bottom sprorcket was ok :roll:
 

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Discussion Starter #9
djtaylor said:
Always a good time to also change the head gasket as there aren't that many more bolts and oh, while you're there, get the alternator checked, particularly brushes and change all the water and oil O rings, both idler pulleys, front crank oil seal and stick on a nice new belt at the same time.

Set you up for another 100k miles.

Timing chain or balance shaft chain, in my opinion, you have to remove the cover to inspect it all. It simply isn't enough to remove the cam cover and look at the cam sprokets as many seem to want to. As the Saab mechanic said, it's the balance chain and there are 5 more sprokets that can't be seen without the cover off.
David.
Yes, did just about everything that David wrote above and then some (clutch, cylinder head, dampers etc...). Also, the cyl. head was cracked, one of the cracks didn't hold in the pressure tests (so it was all the way from the combustion chamber to the channels), another known weak spot for the early B234 Turbo engines...I was lucky enough to find a recently refurbished head (new hydr. lifters, valve rubbers etc.). Right, but now I've got a silent as a whisper engine that's MUCH more responsive. All is well now for another 100-200kmiles :cool:

-Ville
 
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