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Discussion Starter · #1 ·
Thank you in advance for any and all help with this problem.

The wife's 9-5 wagon sounded like a small diesel motor when at normal operating temperature. We had purchased it used and immediately checked for the sludge issues. Cleaned and flushed the crankcase per instructions found on the forums. Performance improved but the diesel sound continued. Consistently setting number 3 misfire and complete loss of power brakes at random times.

Check compression and readings were low (20 to 30 psi below 155 psi) Added oil and rechecked compression with results about 10 to 20 psi increase across all four.

I decided tear down the motor (in chassis) to find out what was going on.

With the crank at TDC, the intake cam was 6 degrees advanced and the exhaust cam was at least 3 degrees retarded. (which could explain the lack of compression during the oil test)

Found evidence of piston slap on three of the four cylinders. Piston #1 is the worst of the three (see picture). Piston #2 is half and #4 is a quarter as bad when compared to #1. I also found the oil control rings were compressed fully into the piston and would not rotate.

I have three replacement pistons, full set of rings and bearings. (oddly enough the bearings are perfect)

I need advice on how to flush the piston cooling jets prior to reassembly of the motor. Still need to mic the cylinder walls, although they all still have the cross hatch from the factory and significant varnish from the cheap oil the previous owners were using.

The rebuild plan includes replacing the timing chain and installing the update #6 to the PVC system. Any other suggestions?

Thanks in advance... I need to get this done quickly, the wife is driving my truck... she ain't happy.:roll:
 

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What did you find when you checked for sludge? How did you inspect bearings, visual?

In the end I think your going throw the replacement pistons in and do a compression test. Then another test at the next oil change.
 

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Discussion Starter · #3 ·
Thanks Norm, when we got the car it had major sludge was in the pan. I cleaned the pan, ran fresh oil for 500 miles. Before I changed the oil, sea foam 30 minute idle and flush. (not quite as confident to do the 3 quarts of diesel with 1 quart of oil in a Saab... Chevy 350... sure, boosted four banger not so much)

The attached picture is the bottom bearing from the #1 piston, comparison to the brand new bearing.

The more I think about it the more I think the oil control ring sticking is the biggest culprit. While it doesn't have the same level of tension against the cylinder wall as the compression rings, it still would serve a major role in keeping the piston from tilting on the power or compression stroke.

While the following link is for Subaru, the tech makes a great explanation of the cause. Supporting the idea that the stuck oil rings are a cause for the slap. The rings get stuck because of the sludge.

http://allwheeldriveauto.com/subaru-piston-slap/#comment-109771


I am still as a loss as to how I can flush or clean the oil journals (piston jets) to ensure I don't have a repeat.
 

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But if bearings are good what caused the slap? Sometime the wrist pins fail but all 4?

THe jets are actually quite cheap I usually replace them but that was before the lack of parts supplies hit, but there may be some somewhere
 

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The jets for 1,2,and 3 come out easily from the bottom, you can pull them out and soak them in a solvent. #4 gets blocked by the cps wheel, I usually run a pipe cleaner or flexible piece of wire through it in place

Since you didn't find any sludge, I suggest checking for a lean running condition after you get it back together. Easiest to find if you can get hooked up to a tech2, you want to check for airmass deviation and proper fuel adaptation. Won't necessarily trigger a cel
 

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Discussion Starter · #6 ·
So I took some really high res pictures of the pistons and the cylinder walls. After reading several posts about piston slap, I am pretty certain that the oil sludge problem is the critical point.

Here is my non-engineering degree theory:

The oil is cooking in the oil control rings and thus gluing them into the grooves on the piston. Once the rings get cooked and stuck, the varnish begins to form on the cylinder wall. The rings are no longer functioning with the force to stabilize the pistons lateral motions on compression and power strokes. The scoring on the piston skirts correspond with less on the compression side (front skirt) than the power side (rear skirt).

I think because the cam timing was so far off, the engine was not producing enough power to really tear up the cylinder walls and bearings. I think the flush stopped any damage to the bearings, but it was too late for the pistons.

Are there any techs out there that can confirm my theory or tell me I am full of crap?
 

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I think its more heat related, the wrong oil was failing to lubricate thus building up the heat in the piston cylinder.
It looks like you were about 1-500 miles short of seizing the engine and or throwing a rod.
Good timing! (On your part not the car)
If you wanted you could go for oversize pistons, I think they are 100 mm.
I little more work though.
 

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Agreed with the "heat related". Cam timing being off can basically stop fuel adaptation, giving you a lean running condition (which is HOT)

Oversized pistons (if needed) would be 90.5mm or 91mm. If you need to go that far, I'd go to 91mm forged pistons. Not cheap and you'd pick up the expense of having the cylinders bored at a machine shop

check out some of the procedures here: http://www.serioussaab.co.uk/archive_pages/p_archive.html Great info for rebuilding your Saab engine
 

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Discussion Starter · #9 ·
Thank you for the input. I haven't been able to micro the bore on the cylinder yet, my neighbor who is an engineer is going to help me with that using some of his high end tools (at the rather bargain rate of a case of "Blue Moon" ale) later this week.

The factory pistons are #3 size and I have a spare set of #4. So we are going to measure them for comparison and see if there is a benefit to running the #4(s).

The wife loves this car, so I have to get this perfect... if momma's happy, then life is good.:p
 

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What'd you ever end up doing? I'm in sort of the same situation. I decided to have the cylinders re-bored and I'll be ordering oversize pistons, but I'm still looking to fix whatever caused the lack of lubrication in the first place.
 

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d boy, were you getting an oil light? There's lots of reasons these engines fail, not necessarily lack of oil pressure. For example, hydrocarbons from lack of pcv will stick rings in their grooves so they cannot work properly and your pistons start slapping
 

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Discussion Starter · #12 · (Edited)
d boy, were you getting an oil light? There's lots of reasons these engines fail, not necessarily lack of oil pressure. For example, hydrocarbons from lack of pcv will stick rings in their grooves so they cannot work properly and your pistons start slapping
D boy, N.E. Swede nailed it. My oil control rings were seized into pistons.

My final solution was to replace the pistons, rings and bearings. My cylinder walls were in really good shape, so I ran a bore hone (brush type) to break the glaze. Ended up having to replace two of the exhaust valves on #4. Basically because of the failing PCV system (pre-update 6) the motor was sucking oil. Prior to the engine tear down, I did a serious flush using kerosene and oil mix.

End result, first thousand miles smooth as silk. Piston rings set right away. She (Aunt Fanny) as my wife calls her Saab, hit triple digits in very short order. ;ol;

Hope this helps.
 

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d boy, were you getting an oil light? There's lots of reasons these engines fail, not necessarily lack of oil pressure. For example, hydrocarbons from lack of pcv will stick rings in their grooves so they cannot work properly and your pistons start slapping
At the time I bought the car (already knowing the engine was knocking) there was no oil light. Never was as long as I owned it. Previous owner had never updated the PCV :nono;. That is part of the re-build for sure. When I pulled the pistons out all the rings were freely moving. I believe my piston slap is coming from too much clearance between the pistons and cylinder walls, plain and simple. I think lack of oil is to blame because of several reasons:

  • There was some clogging in the sump screen, but not terribly.
  • The #3 main bearing was shot, which in turn may have led to low oil pressure
  • Looks like the balance shaft bearings are quite loose, which again may have lowered oil pressure. Anybody know how loose is too loose, by the way?
Turns out the #3 bearing oil passage is directly connected to the balance shaft oil lines. I suspect one bearing went, and then shortly after the other went. Either way, what was once slightly low pressure caused one bearing to go, further lowering the pressure until the next bearing went, and from there the piston jets lost enough pressure to be effective. End result - premature piston skirt wear :cry:. What's why you should change your oil properly and watch your oil pressure ;)

D boy, N.E. Swede nailed it. My oil control rings were seized into pistons.

My final solution was to replace the pistons, rings and bearings. My cylinder walls were in really good shape, so I ran a bore hone (brush type) to break the glaze. Ended up having to replace two of the exhaust valves on #4. Basically because of the failing PCV system (pre-update 6) the motor was sucking oil. Prior to the engine tear down, I did a serious flush using kerosene and oil mix.

End result, first thousand miles smooth as silk. Piston rings set right away. She (Aunt Fanny) as my wife calls her Saab, hit triple digits in very short order. ;ol;

Hope this helps.
I'm still on the fence about just putting in new stock-size pistons. I have the money for machining and new Wossners, but I'd rather keep my money if I could. There's enough scoring on the cylinder walls to make me nervous, though. Maybe I'd get away with it, maybe I wouldn't. Don't want to waste all this work just to develop new problems. I actually have a thread going on that matter here: http://www.saabcentral.com/forums/showthread.php?t=238091

Did your cylinder walls have any scoring? Ever get a chance to check out other bearings throughout the engine (i.e. balance shaft bearings, cam shaft bearings)?
 

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Discussion Starter · #14 ·
D boy, Sorry this is long.

The machine shop that installed the new valves checked the bores for the cams since they don't have separate bearings. They checked out fine. Since I did the job with the motor still in the car, I didn't check the balance shaft bearings. The rod bearings were in really good shape, the mains showed no sign beyond normal wear.

The cylinders checked out fine, no scoring of the walls. My theory is the oil control rings being stuck in the piston grooves reduced the piston stability on the compression and power stroke. Thus the difference in damage on opposite sides of the piston. My cylinder walls were varnished pretty bad from the oil being baked versus scrapped, so I was able to get by with a light clean up of the bores.

After reading your other thread, I think we both were dealing with the same issue. I am guessing I caught a break doing my motor a bit sooner. I had the exact same problems. Just my bearings didn't reach critical mass like yours. If you have the cash to do the job with the upgraded pistons, I would give it serious thought. You would have the advantage of having the machine shop hot tank the block and clean out all the journals. You could install new balance shaft bearings and all new timing chains. I did replace my cam timing chain when I did the job (that was a real pain to get timed), but wish I could have done the balance chain as well.

Thanks to the previous owners lack of maintenance I will be replacing the turbo because it is leaking oil through the bearing. The oil journal was coked up pretty bad, so I am guessing it was starving for oil.

Hope this helps, I am nowhere near a Saab expert.
 

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Discussion Starter · #15 ·
On the matter of the lack of lube through the motor, lots of threads out there on the subject. My two cents... Poor maintenance, Heat load from Cats under the #3 and #4 pistons, PCV problems, and crap oil.

I flushed my motor with a solution of 3 quarts of kerosene and 1.5 quarts of oil. Drained the old oil out with the motor hot. Put in the flush solution, new oil filter either Mobil One or K&N. Started the car an idled for 30 minutes (DO NOT REV THE ENGINE, OTHERWISE THE BEARINGS WILL BE DESTROYED). The solution was as dirty as the old oil I had just drained. After draining I pulled the pan, chunks of paraffin were in the screen and the bottom of the pan. Probably not the recommended method by subject matter experts, but it has worked well for me over the years.

I use Mobil One Extended Performance and Mobil One oil filters, changes are between 3500 and 5000 depending on type of driving. Trying to figure out a way to shield the oil pan from heat without increasing wind noise or effecting the cats.
 

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Longbow-06,

Thanks for taking time to reply. I wish I got off as lucky as you. After tearing apart my engine I'm convinced the previous owner was rather abusive. Wish he would have stopped driving it as soon as it developed the knock.

I've got enough scoring in the cylinder walls that I feel a re-bore is necessary, so I think that's the way I'm going to go. I'll be doing a hot tank just like you mentioned, and in fact I've already changed out the cam timing chain. I think I may have a problem with my turbo like yours, too. The few times I drove the car to get a feel for the way the engine was running, I remember seeing a puff of smoke after I let off the gas. I've read that means the turbo's on the way out. Considered doing a rebuild? Any good info you've found on that matter?

Engine should be in tip-top shape when I'm all done, but I want to make sure it stays that way, which means making sure oil is getting where it needs to be. To make sure of it, I will have installed new main bearings, new rod bearings, new balance shaft bearings (inner and outer), new o-rings throughout the oil system, pcv update, and possibly a new oil pump too. Might wait until after I have the engine running on the oil pump - that will allow me to hook up a oil pressure gauge and see if it's doing its job or not. Oh, and of course nothing but full synthetic oil and regular changes ;)

I've also read that a lot of heat comes off the cat converter. I don't remember where I saw it, but somebody on here mentioned attaching insulation to the bottom of the oil pan just above the cat converter. Not sure what type of insulation, but it sounded like a good idea and certainly couldn't hurt, right?

What do you think? Anything I've overlooked?
 

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Discussion Starter · #17 ·
D_Boy, Sorry for the delay. Sounds like you have a great opportunity to dial in your motor. If the funds aren't an obstacle I would punch the motor out to the over-sized sluggers.:cheesy:

Are you thinking about building your turbo or having it built? I have heard horror stories about rebuilds gone bad?

I have not found a method to vent the cat with increased air flow yet, I have found a couple of improvised "heat shields".

Keep us updated on your progress.
 
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