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Discussion Starter #1
PART ONE

We bought a 1997 GM900 Vert on impulse after seeing it on ebay, as you do; 113000 miles with what the seller described as a 'slight bearing noise' coming from the front of the engine. After prodding in the general area with a long screwdriver held to my ear I diagnosed the noise to be one of the idler pulleys. I also read up on the forums about the common GM900 issues (and now believe my car suffers from most of them !) and in particular I was concerned about the loud 'rattle of death' when starting from cold. So the day after buying the thing I did some research on the forums and decided to whip the cam cover off and have a nosey. The top-end looked pretty black, but what stuck me was that the chain didn't look quite right. It appeared to be skewed, as if being forced over on an angle:



The effect on the cam-timing was pretty impressive. I turned the crank with a socket until the cam TDC marks lined-up:



....and this is where the crank was!!!



I initially thought that the chain must have jumped a link, but actually I now think that this was simply because the chain was longer than it should have been.

Whipping the tensioner out confirmed excessive chain stretch (yes, this is after I removed the centre bolt first):



CONTINUES ...
 

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Discussion Starter #2
PART TWO

I read that the engine had to come out to change the chain, but found a post on one of the forums where someone had managed to do it by removing the mounts and pushing the engine to one side. Not having a hoist I thought it was worth a try. After cracking off the crank pulley I removed the exhaust downpipe and both of the front mounts, supporting the engine on two trolley jacks.

This allowed me to slide it across towards the battery giving a couple of inches clearance:



The cover was pretty sludged:



As was the sump:



The strainer wasn't as bad as I expected to be honest:



CONTINUES ...
 

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Discussion Starter #3
PART THREE

Comparing old and new chains side-by-side shows just how much the original one had stretched:



It's hard to see on this pic but the teeth on the bottom sprocket were worn at an angle:



The balance chain guides didn't look too good either:



I cleaned everything with oven cleaner, I found it great at removing the baked on carbon. Here is the sump after a good scrub:



CONTINUES ...
 

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Discussion Starter #4
PART FOUR

I took my time putting everything together. Here is the new chain:



On the new sprockets:



I packed the oil pump with Vaseline before fitting and spun the engine over with the fuel pump fuse out to build up oil pressure. On starting the engine for the first time I noticed that the chain was lovely and quiet, much to my relief !!! What struck me is that the engine appeared to be running fine when I drove the car home after I'd bought it, the only hint that I had chain problems was the rattle when cold which disappeared as the engine warmed up.

Cheers,
Chrisall.
 

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Thats wicked and scarey at the same time.. The only warning was a rattle when the engine was cold.. Another SAAB saved from the beakers..
 

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I recently noted a slight camchain rattle on my 1999 lpt 9-3 which has done about 95000 miles. Upon removing the plastic cover over the throttle I saw that the rubber nipple that attaches the breather to the cam cover had disintergrated. Upon removing what was left of it I saw that parts of the nipple were in the camcover which I removed as a result. No sign of any sludge but there was plenty of baked on "varnish" which I cleaned off. I did notice that the camchain itself had worn unevenly as in the picture, it was however very slight. In fact I thought it was an optical illusion until I saw this post. There is a lot more miles left in it yet though.

My point is that for the chain to wear unevenly, surely the crank and cam sprockets must be out of line, anyone else got any veiws on this? This seems to be born out by the uneven wear on the crank sprocket. When I eventualy renew my timing chain I shall run a straight edge across the sprockets and check the alignment. I wonder if this could be corrected with shims?

Anyway once everything was back together with the new nipple fitted, guess what, no chain noise! The open hole caused by the original nipple disintergrating was amplifying what chain noise there was.

The next job is to drop the sump, just for peace of mind.

Excellent post by the way.
 

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Discussion Starter #11
.......
My point is that for the chain to wear unevenly, surely the crank and cam sprockets must be out of line, anyone else got any veiws on this? This seems to be born out by the uneven wear on the crank sprocket. When I eventually renew my timing chain I shall run a straight edge across the sprockets and check the alignment. I wonder if this could be corrected with shims?
........[/b]
I thought it was an optical illusion at first too! What happens when the chain stretches is that the pins holding each link to the next stretch thus each individual link sits at an angle rather than them all being in line. I saw it quite clearly when comparing my old and new chains. This caused uneven wear on the bottom sprocket, wearing each tooth at an angle. The pics I posted don't show it clearly but I'll try and take some close-ups & post an update. I'm certain that the sprockets were perfectly in line else I reckon it would have thrown the chain.

I would strongly recommend you remove the tensioner and measure how far extended it is, as it's easy to do and is a good indicator of how stretched your chain is.

Cheers,
Chrisall
 

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I will take issue with you on the chain wear. I have been on the motorcycle scene for over forty years and the only time I have seen chain and sprocket wear like ours ( in fairness yours was much worse than mine ) is when the there is an alignment issue e.g. on a motorcycle where the rear wheel adjusters have not been pulled up equally on both sides. If everything is accurately inline the chain and sprockets should show even wear.

On my old 9K I replaced the timing chain at about 100,000 and it was worn evenly as were the sprockets.

I checked the chain for wear by nipping the chain tightly across the exhaust sprocket and lifting a link in the centre of that arc, slight movement so there is alot more life in it yet.

Regards

HAL999
 

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Discussion Starter #13
I will take issue with you on the chain wear. I have been on the motorcycle scene for over forty years and the only time I have seen chain and sprocket wear like ours ( in fairness yours was much worse than mine ) is when the there is an alignment issue[/b]
I thought that too but I can assure you that all of the sprockets were perfectly aligned.

Cheers,
Chris
 

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Hey all,

That is an amazing job you did on your timing chain. I just got my engine kit from Genuine Saab and I'm planing on doing the deed this new years eve. Nothing like starting off the new year with a new chain and a cleaned sump. I just clicked over to 110K and after hearing the dreaded "clicking" noise about a week ago, I'm now ready to take my car to the next decade with a new chain. I'm also dying to see what my sump looks like after using AMSOIL for 80K miles. With Saabs bad rep for slugging this is the day of atonement for all that AMSOIL claims. My questions this evening as I plan my attack are as follows;

1. The dowels in the chain cover...how hard were they to remove? Do I need to go buy a slide hammer?
2. The chain markings for TDC; all I need to do is set each cam and shaft to their markings then set the chain to those exact yellow painted links correct??? Does the other chain need to be as precise? I dont see colored links or any real markings on the gears.
3. Why does the new balancer shaft chain tensioner have a push pin in the side of it? Do I pull that out after I install it or before?
4. How exactly did you jack up your engine? I see you removed all the turbo and intake/exhaust connections, but I'm curious what I need below, all I have are 4 jack stands two scissor jacks and one floor jack.

Any help would be appreciated.

Regards,

Al
 
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