In-out play in front balance shaft normal?

[XC92]

So I've been reinstalling everything on the engine front as part of a timing belt job, and as I was about to reinstall the front balance shaft (the one that runs off the balance shaft belt) spacer and sprocket, I noticed that the shaft had some in-out (but NOT side- to side like a bearing was failing) play in it, like 5-10mm or so (just guessing as I didn't measure it). This made reinstalling the keyed sprocket slight harder as I had to pull the shaft out all the way and be careful to not push it back in and thus not be able to key the sprocket. I got it back on and bolted it tight using the belt and something to secure the crankshaft balance shaft sprocket.

But I'm wondering if this play, or any play really, is normal with the front balance shaft. The rear one that you install the oil pump sprocket on doesn't appear to have any play. If it's not normal, am I basically hosed and have to either remove the front cover and see if I can fix it, or just do a BSE? If it is normal, why is there play? Does it service any purpose or is it only there when the sprocket it off and goes away when it's reinstalled?

Also, with the belt on, there's around 5mm of sprocket teeth on the outside of the sprocket that aren't covered by the belt, whereas the crankshaft balance shaft sprocket teeth are fully covered by the belt. Is this also normal, because the smaller sprocket is wider than the larger sprocket? If so, why is that? I assume that all of this has a reason, even if it's not obvious.

 

[DSMPT]

I noticed that the shaft had some in-out (but NOT side- to side like a bearing was failing) play in it, like 5-10mm or so (just guessing as I didn't measure it).

It's normal. Maybe a couple of mm, 10mm is probably too much.

with the belt on, there's around 5mm of sprocket teeth on the outside of the sprocket that aren't covered by the belt

It's normal, too.

But I'm wondering if this play, or any play really, is normal with the front balance shaft. The rear one that you install the oil pump sprocket on doesn't appear to have any play. If it's not normal, am I basically hosed and have to either remove the front cover and see if I can fix it, or just do a BSE? If it is normal, why is there play? Does it service any purpose or is it only there when the sprocket it off and goes away when it's reinstalled?

I could be wrong but I guess it's because the front shaft (RH) is floating and belt driven. The rear shaft (LH) is gear driven by oil pump drive gear, that's why there is no much play.

 

[XC92]

This is the balance shaft that's closer to the front of the car (making me wonder why it's called the rear shaft), that's driven by the balance shaft belt off the crankshaft balance shaft sprocket (i.e. not the one that's closer to the rear of the car that's driven by the oil pump gears).

The play was strictly in and out, meaning that with the nut, sprocket and spacer removed I could pull it in and out around 5-10mm, but there was no wobble or side to side play. This made it slightly difficult to reinstall the sprocket because I had to make sure that the shaft was pulled as far out as it would go and that I didn't push it back in when I reinstalled the spacer and nut. But it wasn't that hard. I just had to be gentle. And when the nut was tightened there was barely any in-out play, 1mm at most if that.

This was during a timing belt replacement job, of course.

What I'm wondering is whether this is normal, or a sign that something's wrong, perhaps whatever retains the front or rear bearing in place failing, and I need take things apart and either fix the issue or delete the balance shafts entirely. Is the rear shaft held in place right-left by the bearings being press fit into a sleeve, or some other mechanism holding it in place? Or is there supposed to be this much play when the sprocket is removed?

I wouldn't have basically reposted the same thread were it not for a couple of additional things that just occurred to me that might be signs of a failing balance shaft.

One, when I start the car, with the proper amount of oil in the engine as indicated by the dipstick, it takes a while for the stock oil pressure gauge on the dash display to pass the first bar, so it appears that oil or oil pressure is low. Eventually it passes that line and stays around the center between the first and second bar. But I heard somewhere that low pressure could be a sign of failing balance shafts, since they have oil openings and pass oil through themselves.

And two, when I pulled the oil pan a few months ago to clean it, I took some photos of the bottom of the block, and one captured the balance shaft in question, and there seemed to be something off by the right end of the shaft, like a groove had worn around the shaft. I'm not sure if this is normal or not but here's the photo:

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One other data point is that when the engine is idling, there's sort of this regular tapping sound, like 3 or 4 each second. I didn't record it and with the timing belt still off the car I can't do so now. But it stands out and I don't know if it's normal or not, especially with a cold engine.

Oh, and this is probably unrelated, but at idle the turbo boost gauge often dips below 0. Not sure if that's normal or not or related to this.

Also, when I tried to loosen the rear balance shaft sprocket nut using the balance shaft belt to hold it in place, the belt snapped, and for all I know it had stretched and been loose for quite some time, perhaps skipping teeth and doing damage to the shaft.

Anyway, should I be concerned and is the shaft failing, or is this all normal and I can finish putting everything back together? This is totally apart from whether I might want to delete the balance shaft entirely as a precautionary measure, which I'd decided against for the time being as I don't race, launch, rev and such, and the car still puts out stock power, so I'm not in the high risk group for cars that still have their balance shafts installed.

 

[DSMPT]

Sorry for replying late. I didn't receive any update notification for this thread.

making me wonder why it's called the rear shaft

The R stands for Right side shaft, not Rear.

is there supposed to be this much play when the sprocket is removed?

That's normal that you have more play without the sprocket (Like 5mm-6mm or so). Because you can push in the shaft more without the sprocket. And the play should be way less with the sprocket but it should still have some play (Should be like a mm or maybe max 2mm or so)
I can't be 100% sure since I haven't checked your engine by myself but I don't think you need to be worried much about this in/out play, if I understood what you mean well, then this sounds normal to me. But if you see side to side or up/down play, yes you should be worried.

Also, when I tried to loosen the rear balance shaft sprocket nut using the balance shaft belt to hold it in place, the belt snapped, and for all I know it had stretched and been loose for quite some time, perhaps skipping teeth and doing damage to the shaft.

To be 100% sure, you have to disassemble and inspect, but I don't think you damaged the shaft or bearing by doing that. I don't know how hard you did but people even use an impact wrench to loosen that bolt. And the balance shaft bearing clearance is not as sensitive/strict as rod/main bearings, so actually even if you got some small scratches on the bearing it would work as long as if it has a good oil pressure and proper clearance.
Turn the shaft by hand and if it rotates smoothly without catching anything (but you would probably feel some centrifugal force), then probably there is no problem.

 

[XC92]

Yes, no side to side, up-down or wobble-type play. Strictly in-out, or axial, that basically goes away with the sprocket and spacer installed and nut with washer locked down, with perhaps 1mm still there. Several people have told me that this is all normal and I shouldn't worry, so I've started putting everything back on and should be done soon.

The one remaining "hangup" is accessing that rear bottom engine bolt so I can insert a screwdriver to make sure that the rear balance shaft is rotated properly when aligning the timing marks. with the t-case, exhaust, cross member, CV axle and A/C compressor in the way, it's all but impossible to get enough access to it, and I really don't want to remove some of these to get to it.

So I'll probably use the other method of balancing it, spinning it to make sure that it wants to rotate CCW, not CW. I've already torqued it down using a pry bar on one of the teeth and a torque wrench. They really designed things tight on this car.

 

[DSMPT]

I have a complete 6bolt engine for parts and still all belts are installed, and was running when I got it many years ago.
I took a video, maybe it would make you relieved.

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[XC92]

Yes! That's exactly what I saw with everything off. I'd already realized that this was fine, but this makes it that much "finer". Thanks. In an alternate reality I'd write an alternative version of the FSM for real people, that includes such arcane oddities.

An aside, but I can't believe how long it's taking me to do the TB job. Of course I'm replacing nearly everything, including all 5 seals, 5 belts, pulleys, etc. But mainly I'm spending so much time cleaning parts, plus it's been cold and I've had a bad cold. Everything seems 5 times slower. Today I cleaned the valve and top cover, and a small engine mount part. I hope to finally finish tomorrow.

 

[pauleyman]

Yes, no side to side, up-down or wobble-type play. Strictly in-out, or axial, that basically goes away with the sprocket and spacer installed and nut with washer locked down, with perhaps 1mm still there. Several people have told me that this is all normal and I shouldn't worry, so I've started putting everything back on and should be done soon.

The one remaining "hangup" is accessing that rear bottom engine bolt so I can insert a screwdriver to make sure that the rear balance shaft is rotated properly when aligning the timing marks. with the t-case, exhaust, cross member, CV axle and A/C compressor in the way, it's all but impossible to get enough access to it, and I really don't want to remove some of these to get to it.

So I'll probably use the other method of balancing it, spinning it to make sure that it wants to rotate CCW, not CW. I've already torqued it down using a pry bar on one of the teeth and a torque wrench. They really designed things tight on this car.

If you just put a fresh seal in that "wants to rotate" method probably won't work anymore.

 

[XC92]

I've noticed that, but it still shows a slight tendency to prefer going one way than the other, depending on number of rotations. But how to access that damn bolt to make sure? What an incredibly stupid design, hey, let's put this bolt that can make the difference between a smooth running engine and one that could vibrate itself to death in a place that can't really be accessed, at least in a fully loaded model.

It never ends, does it?

 

[pauleyman]

I haven't done it in years but I could swear I didn't have too much trouble. 1g has a lot of room if you remove the battery. You can stick your arm behind the manifold. I know I've changed a knock sensor without removing anything.

 

[XC92]

Thanks, this was the key, going in from the top and right. Just enough room to fit my arm and some tools. Got the bolt out, inserted screwdriver, confirmed the oil pump pulley was rotated the correct way, and was able to get the TB back on. Things went much slower than I'd hoped, but that's usually been the case.

Tomorrow it should all be done. Just some finishing up I wasn't able to get to because it got dark.