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Discussion Starter #1
We did this a long while ago, where we become paranoid that our timing chain is rattling away. Well, that paranoia has hit me hard. Cleve, this may be a thread to put in the FAQ that you're putting together, the topic comes up every once in a while. I've got rattles coming from every which direction, but the one I worry about the most seems to be coming from the timing side of the engine (coincidentally also the serpentine belt side :roll: ). Sound isn't too loud, can just barely hear it over regular engine noise. Rattle sound does speed up with the engine, especially when accelerating (I can hear it if my window is open and the speed is low enough that air noises doesn't block it.) Engine as I understand, has roughly 110K miles on it. So today I decided to pull the timing chain tensioner and have a looksy. First you remove the small bolt on the tensioner, which holds the spring and a plunger in the tensioner. Be careful when removing the spring, my plunger came out with the spring and fell to the ground, was lucky it didn't get caught up in anything. Next part is removing the tensioner itself, I believe it requires a 27 mm socket. Once thats out, presto, you have your timing chain wear indication. My understanding is that you don't want it to exceed a length of 11 mm, but 11 mm from where? Here's mine fresh out of the engine, with a centimeter ruler up against it:


So where am I measuring from? I've put the photo up again below for illustrative purposes. First choice, Number 1: Measuring the exposed teeth/ratchet points, which each measure a distance of 1 mm between each one's peak (7 teeth visible, 7 mm from tensioner housing to end of teeth)? Number 2: Measuring from the inner vertical edges? Number 3: Measuring from the outer vertical edge?

Any thoughts you guys might have would be great. I'm hoping that its actually the tensioner or an idler pulley, can't seem to find when the last time they were done by the previous owner who kept pretty good records since the car hit 59K miles (when he took ownership I assume). Could that possibly cause this rattling.
 

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Wow - Awesome post Nathan!

How did you get the tensioner out? I had thought that it was well burried under one of the accessories?

OK, well Alldata is useless, but I imagine you knew that already. It might be worth checking the bentley guide for c900's. I vaguely remember seeing a picture there, but I gave mine away when I sold my old car.

I've got a related question. In my c900, remember the chain between the camshafts was very tight, you could couldn't move it with you fingers. The one on my ng900 has a little play. Is this normal? It doesn't make any noise. I hope it is, then I can ignore S4L and go back to feeling paranoid about sludge. :eek:
 

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Discussion Starter #3 (Edited)
Actually, it wasn't hard to get to at all. Was just a matter of removing air intake from the plenum to the air mass meter and then look at the passenger side (US) of the engine at about the same height as the evap. purge valve. No serpentine belt driven accessories had to be fiddled with. For the bolt that holds the spring and plunger in the tension (awkwardly off-center on the tensioner, that was a sure sign I was in the right place), I did use a socket extension or two so that I could get better revolutions of the socket wrench, once that was out I used my large torque bar (only thing I had that would fit 1/2" driver that the huge 27mm socket has). It was a little bit of fun trying to get that to fit within the confined space (cruise control cable and iac piping where right in the area). Not too much trouble presented by the serpentine belt. I'll take some photos tomorrow of it's location. It was a lot easier to get to and check it's tension than I thought. One thing I noticed is that the tensioner had many more teeth that could come out than I found my tensioner to be at, perhaps even go out to just under twice the length mine is at. Reinstalled, started it up, still a noise. Might have to start dreading the thought of the balancing shafts' chain. Now that one from what I have seen/read, is a bit more involved to check the tensioner status (seeing how it's located within the engine).
Perhaps for the heck of it while it's on my mind I will follow Brewtide's timing chain replacement via master link chain directions and get it over with later this spring or summer. If that tensioner is saying the chain isn't stretched too much yet, it will be with a year or two I bet. Definitely take lots of pictures of that if I do it.

JMarkert said:
In my c900, remember the chain between the camshafts was very tight, you could couldn't move it with you fingers. The one on my ng900 has a little play. Is this normal? It doesn't make any noise.
With my NG900 last summer when I did the valve cover, the chain between the camshafts was tight, I couldn't depress it. Do the timing marks on the cam sprockets line up correctly?
 

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With my NG900 last summer when I did the valve cover, the chain between the camshafts was tight, I couldn't depress it. Do the timing marks on the cam sprockets line up correctly?
I should of looked while I had the valve cover off. I assume they're fine since the motor runs nicely and I don't get much noise from the chain at all. If I take the cover off again I'll take a look. Right now I'm doing the auto-rx thing (which I'm still half convinced is a cult). I have some nice "before shots", so maybe later this summer when I'm done I'll take off the vc for some afters and look at the position of the cams etc.
 

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as far as i know, it's 11mm (i've heard 14mm, but whatever) from the inside end of the plunger aparatus. The reason I say this is because the way the tensioner works; that part of the plunger, the very end, is what actually PUSHES the guide right into the chain, thus, tensioning it. The gap between, 2 in your diagram, is what is actually extending itself.

Seems to make the most sense in my head, at least.

And just to let you know, if your guides and sprockets DO look okay, go ahead and try that master link fix. I've done it myself over a weekend, and it's not too rugged to do. I posted a while back (a month?) about how to do this and what you'll need to use. It's actually pretty simple just be patient, get a seperate set of hands and DON'T drop anything into the void; that'd suck pretty hard. Also, If i recall, after you break the existing chain, i found it easier to pull the top piece of chain towards the FRONT of the car, as opposed to the other way. I used a dremel to break the chain and a ball peen hammer to reassemble when complete. Like I said, I posted my 'directions' earlier on this forum.

Hrm, what else. Oh, when you do fit a new chain, i figured it was better to assemble and crank the wheel around by hand to let the tensioner take up the initial slack of the chain, slowly. The tesioner moved in on my car , say, 3-4 'clicks' on the ratchiting mechanism on the tensioner itself. I figured this to be normal.

I only changed my timing chain, no sprockets and guides, and it's happly went another 15-20k without any noise at all. (does have tranny issues, but that's completely unrelated..).


Good luck, be patient, it can be done, and it cost me like $60 incuding a new valve cover gasket!

peace,
bny
 

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Discussion Starter #6
Oh, I brought your directions into this in my second post. I plan on following your's if/when I do it. Do you happen to recall the engine number for the 2.3 9000? I ask because the NG900 S models use a 2.3L also, number B234i. When you did your timing chain change, did you bother to use the tensioner as an indicator? If you did do you recall what your measurement? The 11mm measurement I stated earlier in this thread I read from that post where you wrote the directions. Where did you guys find that length? I check alldatadiy.com and I can't located that number (can't locate any length measurements at all). Only thing they have under specifications is the torque when putting the tensioner back in the car.
 

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The engine is a B234, but I am unsure of the 'i', I forget what all the letters mean, but if I recall, the i means it's an n/a - And Mine was an n/a. Sorry, but I know it's the B234 at least. Perhaps the 'i' stands for balance chain? One second, lemme dig out the haynes...

Okay, i was right the first time, i is for the n/a engines, all B234's have balance chains, vs, the B202's which are without, I believe.

As far as the length, I believe it got it from a scanned copy of an official saab documentation on timing chain repair, that I scarfed off the web somewhere. Actually, i was on the saabmaster website; I just checked for the actual document, but it's run on some guys cable modem / dsl computer, and it takes him a while to update his IP to the domain when it changes(!).

http://www.townsendimports.com/

click the 'saabmaster' link; it's up sometimes, down others. Just keep trying! The PDF file is on there somewhere, when it's up and working (very frustration, I know, I need to mirror the information on my site!).

My tensioner, was at 14 or so mm, that's where I'm recalling that measurement from. Sorry about prior confusion. At 14mm (or so) , the tensioner was FULLY EXTENDED, so it was just blatently obvious that it needed to be done (aside from the horrible horrible slapping sound, heh).

That again makes sense with their 'time to change at 11mm' statements that weve been beating around, as it allows for a little bit more time until the tensioner is simply worthless. Make sense?

Like I said before, it's not rocket science, and I had 4 mechanics (and my parents, haha, which is worse?) telling me that it was a bad idea, but it was successful. I've always been one of those 'stubborn' people, but after I had read up and brought myself upto fully confident, it was go time.

As many other stated, this isn't the 'end all' solution, esp. if it's been slapping for a while (causing your guides or sprockets to wear..) but if it just started and you caught it early, I wouldn't think about a full tear down.

If your balance chain is slapping, then it's a different story; mine was fine, and I've actually read, on these forums, of people taking theirs OUT and having (again, this is internet hearsay, heh, ) that there was no vibrational difference. *shrug*.

Go for it, as long as you do this procedure sucessfully, even IF it starts slapping again (or the balance chain makes noise, later on) you're out what? $60 ish dollars and a bit of time.

But in that same note, you've learned and feel quite accomplished when everything starts back up!

peace,
bny

good luck.
 

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Slaab4life said:
We did this a long while ago, where we become paranoid that our timing chain is rattling away. Well, that paranoia has hit me hard. Cleve, this may be a thread to put in the FAQ that you're putting together, the topic comes up every once in a while. I've got rattles coming from every which direction, but the one I worry about the most seems to be coming from the timing side of the engine (coincidentally also the serpentine belt side :roll: ). Sound isn't too loud, can just barely hear it over regular engine noise. Rattle sound does speed up with the engine, especially when accelerating (I can hear it if my window is open and the speed is low enough that air noises doesn't block it.) Engine as I understand, has roughly 110K miles on it. So today I decided to pull the timing chain tensioner and have a looksy. First you remove the small bolt on the tensioner, which holds the spring and a plunger in the tensioner. Be careful when removing the spring, my plunger came out with the spring and fell to the ground, was lucky it didn't get caught up in anything. Next part is removing the tensioner itself, I believe it requires a 27 mm socket. Once thats out, presto, you have your timing chain wear indication. My understanding is that you don't want it to exceed a length of 11 mm, but 11 mm from where? Here's mine fresh out of the engine, with a centimeter ruler up against it:


So where am I measuring from? I've put the photo up again below for illustrative purposes. First choice, Number 1: Measuring the exposed teeth/ratchet points, which each measure a distance of 1 mm between each one's peak (7 teeth visible, 7 mm from tensioner housing to end of teeth)? Number 2: Measuring from the inner vertical edges? Number 3: Measuring from the outer vertical edge?

Any thoughts you guys might have would be great. I'm hoping that its actually the tensioner or an idler pulley, can't seem to find when the last time they were done by the previous owner who kept pretty good records since the car hit 59K miles (when he took ownership I assume). Could that possibly cause this rattling.
So then, if I have this right,, and if not, I will edit - The exposed teeth are to be counted (shown as the red 1); in this case 7, which is very good.
4 - maybe this is as new
7 - normal for high miles
11 - the wear limit
14 - fully extended, slapping will occur

IMO, during the extensive 100K service, the tensioner must be removed and measured, this number must be reported to the car owner.
I will do mine when the rain stops and the temperature is mild..
'96 900S, 143K miles..
Right now, all is quiet on the engine front.
 

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Discussion Starter #9
I really hope earthworm is right and that the measurements are based upon the ratchet teeth (then again if its not the TC, then it might be something more sinister). 7 sounds like a healthy number for an engine thats gone 110K miles over 8 years. For those interested but haven't dived in to look for their tensioner:

This is looking from the firewall. Luckily no serpentine belt accessories in the way, you can see that their is an idler pully right next to it, but still had enough room to get the big socket in there for the tensioner. Space above the tensioner is limited with the evap purge lines and aic lines running above. With the small bolt, like I said, I ran two extentions on the socket (nearly to the firewall to get better rotation distance when removing), if you have a few 1/2 inch extentions for the tensioner removal, that would be good. I was able to get about an 1/8 of a turn because the torque bar was right at the socket and many things right above. But once you break that initial resistance you can unscrew it by hand (little cramped but possible). It's been rainy all day so I haven't been able to look around much. I did take note today that whether the engine is cold or warm, low or high rpm, the noise can be heard (does speed up with the engine). I have a sound clip, but nowhere to host it. Does anyone know anyone who can host the clip (going to be a .wav file) or care to get an email of it and tell me if I'm just paranoid?
 

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The accuracy of this measurement will not be known until another member chimes in or I check out my own known to be good tensioner.

This will take some time - several weeks anyway..
 

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Discussion Starter #11
So I've read elsewhere that the measurement is #2 on the illustration. Not from an official source though. I've also been told that some people and mechanics are uncomfortable with using the tensioner as a true means to guage the condition of the chain. It was suggested that I first replace the upper chain guide that is mounted on the valve cover. For $6.50 I can't go wrong trying that first.
 

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That, I agree is a good idea.

These wear plates do take a beating and their shape could be an indicator of the chains condition.
And the 900(original) forum should should have some more good info on this matter..
 

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Slaab4life said:
We did this a long while ago, where we become paranoid that our timing chain is rattling away.
If that is paranoia, I could have used a dose a few months ago when the camshaft cover was off. Rolling in a new chain would have been a snap (pun intended). Paranoia will be when I strain the gunk in the sump for pieces of chain guide when I get that far. The only positive bit of news here is that if I had traded the car in a year ago, someone else would now be cursing about the p.o. in this forum... :cheesy:

Thanks to this and other threads and information posted here and elsewhere, I finally checked it yesterday. It was extended past the LAST click, shaft measured just over 18 mm when I took it out, using Dimension 2 in this thread (and also Haynes manual and Alldata diagram)

The tensioner is super-easy to access with either the upper idler pulley or the camshaft cover off. Only a little more difficult if you do not touch anything else (you have to work blind behind the upper idler and belt.

With the upper idler off it took all of 10 minutes to get it out. Another 15 to measure the extension, curse, measure again and satisfy myself it was REALLY extended to the limit. 15-20 minutes more to clean it up and get it back in. Only tools needed are a ratchet with a 6-inch extension, 12 mm (spring retaining bolt) and 27 mm (tensioner housing) sockets.

When I cleaned the shaft carefully, I found the series of wear bars on the back of the shaft (opposite the teeth) as it extends a click at a time over the life of the chain. (referred to elsewhere on the web)

The smallest extension I was able to get when I reassembled the tensioner with the spring and pushed the shaft in was about 9 mm. The maximum extension is 18. I tend to believe those who state that 13-14 mm is about where you might find it after a few years under best conditions.

Given what I have found and the noise coming from the timing cover, I think it is no different from other older 4 cylinder cars with timing chains. Chain wear and need for replacement depends more on the number of starts and not on mileage. Chain life is shortened again with winter driving and hard starts, which is exactly the conditions my car was driven under for several years. The fact that someone gets 200k life out of the chain driving mostly on the hwy means little to the rest of us, regular oil changes and other maintenance notwithstanding.
 

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I checked my timing chain adjuster today and from saab4lifes photo on the number one marking from the photo mine reads 11mm so is this time to change the chain and pulleys or just the chain?

From his photo his only reads 7mm and mine is 11mm and the car has done 115K

Thanks Mark
 

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Discussion Starter #15
Doing both the chain and sprockets is the expensive route, if you do all the sprockets. The one that is down off the crankshaft requires quite a few hours worth of work, possibly even engine-out to get it done. Rolling a master-link chain is probably the most economical way to go, though you don't end up knowing the condition of that lower sprocket. I think the Haynes does illustrate how to do the whole thing with the engine still in the car. Once my chain does need to be done I'll be tempted to take it off the road for a week or so and go through the whole procedure carefully.

Whether or not to even do anything based purely on the chain extention that has occur is kind of a hazy thing too. Most will base it on chain extetion (based on the tensioner), whether or not the rattle is present, and condition of the chain guides (especially the guide mounted to the inside of the valve cover).
 

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Discussion Starter #17
ricot83 said:
couldnt u just change the chain tensioner???
If one was to change out the chain tensioner, it would extend to the same length as the other one. The chain tensioner serves to deflect the play that develops over the years of revolutions that the chain develops. Over time the chain lengthens to a point where the links will seperate or the chain just breaks and wreak havoc upon the timing of the valves and whatnot, resulting in catastrophic failure (these are interference-type engines).
So in summary, its the chain that is facilitating the extending of the chain tensioner.
 

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mpgscott said:
I checked my timing chain adjuster today and from saab4lifes photo on the number one marking from the photo mine reads 11mm so is this time to change the chain and pulleys or just the chain?

From his photo his only reads 7mm and mine is 11mm and the car has done 115K

Thanks Mark
At this point in time I would change the chain, probably the upper guide as well.
Around $60 for the master link chain is not too bad..

More expensive than a belt,but more dependable and durable.

More skill and very steady hands( four of them ?) are necessary..
So, some special tools need to be developed and employed; this does seem to be a one-man job.

If the chain is changed a mite early, before it has stretched excessively, the beating that the sprockets normally take is alleviated.

And does anyone know about these sprockets - do the teeth break ?? I never have experienced this, but my knowledge is limited..
This is one for the Harley Davidson people - I 'm sure they know chains and sprockets better than we do...
 

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