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Discussion Starter · #1 · (Edited)
Hi all,

A few months ago I picked up a 2003 9-5 Linear wagon with 125k miles for very cheap from a lady who had just had it with all of its repair issues. I drove it home blowing smoke and spewing trans fluid the whole way. I replaced the blown Garrett turbo with a Mitsubishi TD-04 and fixed a bad transmission leak (just a loose banjo bolt of all things) to get her up and running again.

The car ran great but the engine still made a chain noise, so I first checked the timing chain tensioner and found it almost fully extended. Mind you, my intention when I bought the car was to fix just whatever it needed to make it a reliable daily driver, as cheaply and with as little work as possible. I was hoping like hell not to have to pull the engine and trans, but I also decided I'd rather go that route than struggle with removing the timing cover with the engine still in the car, as pulling the engine would allow me to replace engine and trans shaft seals and provide easier access to replace bushings, etc.. with probably not much more work than the knuckle-scraping in-car timing cover job. I ended up installing a roll-in master link chain and left the old sprockets and guides in place. Chain slack was now within spec but the engine still made the chain noise.

Now suspecting the balance shaft chain and still not wanting to remove the engine, I opted to drop the sump to check for sludge and clean it out, and remove the balance shaft chain, leaving the balance shafts and tensioner in place to keep their oil passages blocked off but no longer spinning them. I was surprised to find not much sludge, but what I did find was a badly worn #3 center main bearing - both shells were worn through to the copper. The crank journal surprisingly was not too scored and still pretty shiny.

I chose to replace all main and rod bearings with the engine still in the car, along with the oil pump. I had to shimmy all the mains around their crank journals with the crankshaft still in place - not the easiest job, but it worked out. When reassembling the #3 main, the cap didn't want to go all the way down. When the cap was torqued down the crankshaft would not turn. My first thought was that when the block was originally bored for the crank main, the #3 main cap was not tightened down so not enough material was cut away, leaving a hole that was oblong and smaller than the circle it was supposed to be. They'd assembled it that way anyway and allowed it to "burn in" the too-tight bearing. Not an ideal situation but it had run that way for 125k miles already. I decided "oh well, it's f**cked anyway," and reassembled it that way again with a new bearing. After loosening the bearing, turning the crank, tightening it, turning the crank some more, etc.. I finally got it to a point where the bearing was torqued down and the crank would turn, although it was very stiff.

The car started and died a few times as it tried to idle down too quickly against lots of friction, but after a few minutes the bearing had burned in and the engine ran normally. The chain noise was gone and it was very quiet. I drove it for a few days and it ran great. Then one day arriving home from work the low oil pressure light came on at idle. Damn.

I connected a gauge and found that my oil pressure was good when cold, however once it got hot it would drop to about 5psi at idle, 20psi @ 2000rpm. Pretty low. I blamed the fried center main bearing and, again, set out to fix it cheaply to keep my engine alive. My idea was to take the #3 main cap from a junkyard engine to replace mine and install a new bearing again. I do realize why this is bad, each cap being machined with its own block and that cap not "matching" any other engine except the one it was machined with. However, my thought was that it would most likely be extremely close to spot-on, and certainly better than the too-small one I had in place.

Dropping the sump from a 2001 9-5 in the junkyard, I was surprised to find the exact same wear on only the #3 main.

I compared my #3 cap to the junkyard one, and also to the ones from the other unaffected bearings, and found that they were exactly the same size inside. So the cap wasn't the problem. I then went online and did some digging.

I found many discussions regarding the center main bearing and balance shaft bearing failures. Apparently the balance shaft bearings are oiled from a drilling off the center main bearing rather than the main oil gallery. The oil flows from the main gallery through a hole in the bearing shell into the bearing, through the center groove in the shell, and back out another hole in the shell into the balance shaft bearing passage. There are a few discussions out there blaming a pressure drop at one place or the other, causing the bearing to burn, in turn causing the pressure to drop more, in turn causing the other bearings to burn. Worn center main bearings and spun or seized balance shaft bearings seem to go hand in hand. It makes sense that the path through the bearing groove would be fairly restrictive in the first place, and if the bearing is torn up or the center groove restricted then the balance shafts see even less oil. The increased friction on the balance shafts causes increased wear on the chain and sprockets, and sometimes the shafts seize, teeth strip off the sprockets and chains break. Mostly people have blamed blockage of the sump strainer by sludge causing starvation to the entire oiling system. However, I've uncovered an alternative explanation.

I came across a post in an online forum from a guy who'd run into the same problem. He ended up removing his crankshaft and measuring each journal with a micrometer, and found that the #3 center main journal was slightly LARGER in diameter than all the other main journals - enough to wipe out any clearance the bearing was supposed to have. I suspect that this manufacturing defect was present in many of these engines and this is to blame for many of their oiling problems, and I'm floored that I found the same problem on a 2001 as my 2003! 2 years is a long time to still be putting engines together with the same defect. I think this could explain many of the issues people have had with these engines. I would have liked to provide a link to this post, however I cannot for the life of me find it again. The "conspiracy nut" in me can't help but wonder if it's been deleted by an organization trying to cover up this debacle - it wouldn't be the first time a corporation has tried to sweep its mistakes under the rug. However, rather than draw that conclusion I'd like to invite input from others in the Saab community. If my post gets deleted quickly without explanation that will give me a clue, however in that event I think I'll quickly re-post this on as many forums as possible. >:)

Anyway, back to my car. I reassembled it again, this time with another new main bearing on #3, started it and let it burn in again. I would have just used one of the already burnt-in pairs, but upon inspecting them I realized that they had become misshapen in a way that could have allowed oil to leak from between the block and the bearing shell. Amazingly it still runs GREAT! I modified the oil thermostat so that the oil always flows through the oil cooler. It may have been defective in the first place, not allowing oil to flow through the cooler causing it to get too hot and thin out, exacerbating the low oil pressure. It now takes a lot longer for the oil to get hot and the pressure to drop. However once fully warmed up on hot days I still see about 7psi at idle and 20psi at 2000rpm - still pretty low.

I am aware that the B2x5 block was redesigned from the B2x4 with a lower-volume oil pump and shorter-skirt pistons with piston-cooling oil jets in order to reduce friction and increase efficiency. I'm also aware that the balance shaft chain tensioner operates under oil pressure, and people say that when deleting a balance shaft chain the tensioner must be removed and its oil passage blocked off, since if the plunger comes all the way out it will lose oil pressure there. This can only be done with the timing cover removed (engine-out job, by my choice). But, I've also read that the chain can just be cut and removed out the bottom with no other modifications (this is what I did) and that the tensioner plunger will just hit the chain guide and cannot come all the way out. I tend to believe this is true, although I have not gotten in there yet to check.

Since I've been bitten by the Saab bug and I've already upgraded to the Aero-spec turbo, my plan has been to drive this engine into the ground while building a hybrid B234/235 block with all the strongest internals and the higher-volume B234 oil pump and timing cover. Then I will have a solid block and a good basis to start playing with different ECU tunes, make more power and have some fun!

On the other hand, it seems a real shame to let a good-running engine die when it could be fixed cheaply and easily by the right resourceful person. (like me! :)

Obviously I still don't want to have to remove the engine from the car to fix it, because after all that I would want to just install my new, built engine.

The solution I am proposing is to obtain or fabricate a new pair of bearing shells. The new shells would have the same OD as the stock ones and a slightly larger ID to accommodate the larger crank journal and put the bearing clearance in-spec. They would have the oil groove in the center like the stock bearings. The block side shell would have a hole through to the main oil gallery to let oil into the bearing, but no hole through to the balance shaft passage. This would block off oil flow to the balance shafts (which don't spin anymore anyway since I removed the chain) and not allow pressure to be lost through their worn bearings.

In order to determine the ID the new bearings should have, I'd have to mic the journal all the way around with the crank still in the engine - not the easiest task, but I feel it should at least be do-able.

I'd have a few options to source these bearings.

The stock bearings would not work because they already have a hole through to the balance shaft passage. I've seen bearing sets for other applications with holes in the block/rod side but not the cap side, but the Glyco bearings have all the holes in both halves. Maybe there is another brand available with holes in only half the shells? One of the non-hole shells could be drilled for just the main gallery passage. I'd then have to have a few thousandths machined off the inside to get the correct clearance, provided this does not machine all the babbitt off and go all the way through to the copper. I could also try something like soldering the balance shaft passage hole shut, but I'm not at all confident that solder wouldn't just re-melt under engine heat.

A new set of bearings from a different application but with the same OD and no hole for the balance shaft passage *might* exist. I feel this isn't too likely but who knows. Ideally they'd already be the correct ID, otherwise they could be machined on the inside, again provided that machining them doesn't remove all the babbitt. I don't know how I'd go about finding the bearings from this other mystery application, but maybe someone more knowledgeable about bearings could shed some light.

Or lastly, I could have a pair of shells fabricated to spec by someone who is in the business of this type of fabrication. If this doesn't cost too much it's a no-brainer.

All this will involve dropping the sump at least once more to mic the crank - possibly twice if I want to still be able to drive my car while I'm waiting for the new bearing. Also, what if the center main and balance shaft bearings are not the main culprit for the oil pressure loss? At some point this project may grow into more hassle than it's worth and maybe I'd be better off just driving it while building a fresh engine in my spare time. If so then I at least plan to switch from Mobil 1 0W-40 to 15W-50 to help maintain better pressure. What do y'all think?

Thanks again to the Saab community for all the helpful information I've gathered on this and other forums. I look forward to hearing your input. Enjoy your Saabs!


· Registered
8,371 Posts
Interesting post

A couple of things, firstly the Hybrid can't use the 234 timing cover and pump without modification.

Next, why not use 234 bearing shells and modify them with the correct oiling holes

INteresting about the #3 bearing never saw any differences

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2 Posts
Discussion Starter · #3 ·
Thanks for the heads-up J. I heard that the B234 timing cover is missing a boss which the B235 cover has for bolting up the power steering pump bracket. I was hoping to deal with this by using the B234 bracket, and if necessary the pump as well - although I have not looked into this at all, I have no idea if it will fit in a 9-5. I also heard that Saab reverted to the B234 oil pump and timing cover for the post-2008 9-5s. Maybe that version of the cover has the boss needed for the newer style bracket?

I have not yet gotten around to seriously researching this hybrid block build but from what I've seen so far I like the idea of B235 block (has the piston oil squirters which the B234 lacks, no?), forged B235 pistons, stronger rods (either forged aftermarket or from B204 which I hear are the same length as the B235 ones but stronger), T7 head, possibly uprated valves/springs, not sure about T5/T7 cams.

That said, a B234 block instead is not out of the question.

In any case I'd really like to use the B234 oil pump. Is there anything else that prevents the B234 timing cover from fitting on the B235 block, besides the power steering bracket boss?

Thanks for the suggestion regarding the bearings. eEuroparts lists B234/B235 shells as the same item, but there could be an older version available somewhere with fewer holes. I also see that the pre-1994 mains only have one oil hole - perhaps these will fit, I have no idea.
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