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Discussion Starter #1
Driving home a few days ago and my car (89 900S) developed a sudden ticking noise accompanied by some power loss, especially at lower RPM. My exhaust is in the process of returning to its component atoms, so I figured this was likely just a new crack somewhere near the manifold. Nursed the car home with no further development of the issue. Checking things over I quickly discovered that something else was wrong. Exhaust was intact (well, as intact as it was the last time I checked it), but the engine was ticking away and running rough. Isolated the problem to cylinder #2, confirmed spark and fuel, but no ignition and apparently (my gauge is a bit wonky) no compression. Seems like a lot of water coming out the exhaust while running as well, though not clouds of steam (possibly just condensation from sitting overnight).

Determined that the head needed to come off for further investigation. Got as far as pulling the intake, ancillaries, and valve cover today. No obvious carnage in the valvetrain, everything inside nice and clean (I just changed the oil a couple weeks ago). So far the only thing I found amiss is that the timing change tensioner measures 15mm, so clearly the chain is past its prime and needs replacing. Wondering if it slipped a tooth and caused valves and pistons to meet. I'll find out once I get the head off.

Questions:
- I will line up the timing marks and make sure everything is at TDC, then get a new chain in. Any specific tips on installing? Should I be replacing guides as well? What about the tensioner itself?

- Should I need intake valves, they don't seem available from the usual sources. Anyone have a line on these? New or good used is fine.

- Anything else I should be looking at while I'm in there? Cooling system was just done.
 

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Replacing the guides requires removing the cover, whereas replacing the chain can be done without any further disassembly. If there is nothing wrong with the guides, there's really no reason to replace them. The tensioner should not need to be replaced unless it's damaged, but you should replace the o-ring on the top bolt, and ideally the sealing ring around the main body as well.

I was able to buy intake valves last year... I'm not sure where they came from, but I'd guess either thesaabsite.com or eeuroparts.com... Hmmm... it could be that I have a 2.1/2.3 head on the car, and those valves were in production longer/later. I could imagine that. It's unusual to replace valves on these cars, so I wouldn't panic until there's a reason to. I have a whole heap of them if you need a few:


I don't know what's what, but probably most are from B202 heads.

I would plan on replacing all the exhaust manifold studs... non-turbos are less hard on them than turbos, but no point inviting disaster down the road. Consider replacing the alternator bushings and power steering pump bushings as access will never be easier. Check the shift coupler when you're there. Do be careful removing and installing the head, it's easy to break a timing chain guide. Cleanliness is next to godliness, be sure to follow torque procedures. Replace the little rubber elbow hose on the front of the head, maybe even if you did it recently.
 

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Discussion Starter #3
Thanks. In addition to the cooling system, I replaced a bunch of other stuff while I was in doing the front crank seal and oil pump O-ring last winter/spring, so all the alternator and PS stuff is good to go (including the PS hoses). Should look at the shifter though - mine's a bit loose. I've got the exhaust manifold hardware, head gasket, and intake and exhaust gaskets waiting. I'll inspect the guides once I get the head off.

It's also worth adding to the discussion that oil pressure and coolant temperature remained solid throughout (I have gauges), so this is not overheat related, nor do I think something went bad on the bottom end. The ticking definitely sounds like the top end, #2 intake side if I had to guess.

I understand the valves are robust, but given the circumstances I'm preparing for all eventualities, and valves rarely survive contact with a piston intact. If it turns out I need to replace some, I'll touch base with you.
 

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I don't think I've ever heard of a dropped valve on a B202, and the only time I've heard of a stuck valve on a Saab was just recently on a 9-3. I've seen burned valves and valves that don't seat right (carbon deposits, seat damage, etc.) but that's about it. I'll be really surprised if there was any contact. Get back out there and get the head off!
 

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Discussion Starter #5
I got the head off and located the source of the problem.

The head fought me all along the way. Downpipe nuts were completely rusted on, so I decided to pull the manifold off the head. The exhaust cam sprocket would not come off (bolt stuck), so I just pulled the cam. The head bolts were so tight that a 1/2" breaker bar with a 4ft cheater on it just barely gave me enough leverage to break them loose. I dropped the exhaust to move the manifold far enough out of the way to swing the head up and out. But out it came - eventually.

Once I got it on the ground and flipped it over, the issue became fairly obvious. One of the exhaust valves on #2 has a chunk out of it. Fortunately, there is no other sign of damage anywhere, so I think I may have dodged a bullet with the super-stretched timing chain.

The question now is what to do about the other exhaust valves. My gut feeling is to replace them, but I'm less keen on spending extra money on a car that was supposed to be as cheap as possible. What's the hive consensus here: replace all the exhaust valves, or just the one that cracked? I figure maybe wire brush some of the carbon off the pistons and combustion chambers, clean everything up, new gaskets, new chain - anything else I should do while I've got the head off?
 

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Discussion Starter #10
Agreed it seems a weird failure. No damage that I can see anywhere else, not even a mark on the #2 piston. Here's the valve in question.
271961


I can get new TRW exhaust valves for $14/ea - if I'm going to the trouble of replacing them all, I figure I might as well go with new.
 

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Discussion Starter #12
Got the valve out. It is a mess.



Fortunately, it seems to be the only thing that's a mess. A few minutes with a toothbrush and some brake cleaner yielded this:



The biggest fear was for the valve seat, but it looks totally unaffected.



With that dealt with, I cleaned up the head with a pressure washer in the driveway, and then prepped the gasket sealing surfaces for eventual reinstallation. Blasted everything clean and dry with compressed air, then fogged the cams with WD40.




Everything looks fine apart from that one valve. Even the piston and block are apparently unaffected.


So I guess it's now just to clean up the block, replace the exhaust valves (I don't think I can live with just replacing the one that failed), and get everything put back together. Still have no idea what caused the valve to fail.
 

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Man, I really would not eyeball this. You'd be well-served having a machine shop check that head - guides, seats, etc.
 

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Discussion Starter #14
If this were a different kind of car I might agree, but this was a cheap car I bought as just that. Machine shop charges would probably add 50% to my total investment at this point. I've had a bunch of engines apart over the years, and I can feel with reasonable certainty when a surface is not right. I'm confident saying that the seat is fine, and I don't feel any play in the guide. Probably going to replace the stem seals while I'm in there, but beyond those and the exhaust valves, it's going back together once the parts arrive.
 

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I mean, I guess, but not spending $100 for a machine shop and wasting $100 on gaskets and fluids if it's not right... seems like cheap insurance.
 

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That certainly is an interesting failure , You have found the symptom and will repair that , but I wonder what the root cause of the problem is , the valve looks melted as opposed to damage from any foreign object .Is the car extremely lean in cylinder 2 ? perhaps a failing injector ? You should be keen to find the root cauise or the symptom will likely repeat .
I believe in the photo of the cylinder 2 crown you can see the corresponding heat impact to a lesser degree
 

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Discussion Starter #17
Finding a machine shop around here to touch anything for $100 is in the realm of fantasy, sadly. If it were a different sort of project, sure. I'll lap in the new valves and check for good seating, but then it's getting bolted together and sent.

All the piston tops look pretty similar, though I see what you're referring to Aussie900 - I'll look more closely at that, as well as checking the injectors (they'll be getting new O-rings as well, and I've got a new fuel filter waiting to go in). On another forum, a mechanic with many years of experience suggested that it could be cause by a bit of debris holding the valve open for even a few revolutions, and if you look closely at the valve you can see carbon built up around the failure point. Right now that's the leading contender.
 

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That explanation seems the most likely. Such a specific breakage seems like a valve seating problem leading to a hot spot. What caused that buildup is another matter - maybe it's just an old motor, but maybe a clogged injector, low quality fuel, or oil leakage?
 

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Discussion Starter #19
Hard to say. There's definitely some carbon built up in there, but I've seen a lot worse. I'm going to put new stem seals on all the valves, so that should help with oil consumption (though this engine leaks rather than burns oil for the most part). Fuel quality on my watch hasn't been a factor, but I can't say what previous owners did.

My usual technique for cleaning up the inside of an engine is to get it hot and then siphon water into the intake slowly. It burns off in the cylinders and steam-cleans everything quite effectively (think about what a cylinder looks like after a head gasket leak). Hadn't yet done it on this engine, but depending on how much comes off easily with it open, it may be getting steamed once it's all back together.
 

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If a valve sticks open there won't be any combustion and everything would get cooler.
It looks like the erosion you see on a boat prop from cavitation; little explosions caused by micro vacuum bubbles imploding. I bet coolant did that on the hottest spots.
 
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