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Discussion Starter #41
I'm trying to ascertain if it's worth going ahead with the piston replacement - if it's possible the head has been overskimmed or something else has been bent or damaged during the head gasket and timing chain job then of course what good will new piston heads do - the mechanic also keeps repeating that it's done 170'000 miles as if that's extremely high mileage on a Saab but I've never had any engine issue other than head gasket on any Saab in 20 years whatever the mileage.
Of course for 500 dollars this could be a cheap bottom end rebuild and as he did the top end for free I should be laughing all the way to the bank if this solves it but I'm just not convinced - he was convinced it was just the valve lifters causing the sound and I can see embarrassment in his eyes but he's also a stern old swede and they don't like to admit failure ! So I think doing this bottom end rebuild at no labour cost is his way of trying to solve it - but I still have to buy the parts ....
 

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I don't know what he did wrong, you can't know in advance.
It was quiet before he worked on it, now it's in the process of destroying itself (that is not a benign sound). Pistons don't shrink when you take the head off. Get a straight story about why it's making noise and see if you can find a professional who doesn't laugh at it. Run it with the valve cover off, touch a finger to the lifters, the problem will be obvious.
Engines that have been repaired properly don't sound like that. Any court will agree.
 

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You DEFINITELY need to use a 2.1l gasket... the 2.0l motor has a smaller bore than the 2.1l, so the top of the pistons will touch the gasket. That needs to get fixed immediately. There could be damage to the pistons, but maybe not. Only way to know is to look.

WRT to that Haynes passage, I understand the point but Saab themselves don't make that distinction and in the probably 80 head gaskets I've done on c900s I've never had that experience. Maybe if you could slam a motor together in 15 minutes it could show up, but after a few minutes squeezed between cam and valve spring with no oil pressure any additional height on the tappet (if that's even a thing) would be taken of. Truly dubious about that claim.

Edit: Seriously cannot believe that the mechanic didn't check the parts, and didn't notice the obviously poor fitment of the 2.0l gasket on a 2.1l motor. It's QUITE visible.... 90mm vs 93mm!
 

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Discussion Starter #48
I checked the order and the gasket was for a 2.0 - different part number for a 2.1 - I just entered year and model and it hit me with the 2.0 - I didn't flinch - so this could have been my fault all along - I would have thought he'd have noticed but I still supplied it ! Well I guess that's the first thing to do
 

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Discussion Starter #49
Yep - confirmation from mechanic ! He's kicking himself ! He didn't check the gasket I supplied - it has to be what's causing the knocking. Really hoping it hasn't damaged the pistons !!!
 

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Discussion Starter #52
Yes that was never going to happen ! But the mechanics been test driving it everywhere ! Let's hope it's just a case I putting the right gasket in
 

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Discussion Starter #53
So I might be there when the mechanic pulls the head on Friday - as the pistons have been hitting that smaller bore gasket - what am I looking for in terms of damage ?- I mean is some damage ok, am I looking for something obvious ? I mean I know what cracks look like ha - is there a spectrum with acceptable wear on one end and obvious damage on the other ? sorry if it sounds ignorant but I've never gone this far into mechanics and it's good to learn
Troy
 

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Discussion Starter #54
We can say that car has been running like this with the knocking for about 3 hours total at operating temperature
 

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There really cannot be any damage to the piston tops - not only would there be an affect short term, but there would be a worse one longer term. I think you'll be ok since the piston tops would just be kissing the gasket surface and not mashing into it.
 
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