Timing belt, exhaust cam jumped

Dirtbag · Post by **Dirtbag** » 14 Jun 2012, 20:34

I hope I haven't just doomed this project to another two weeks of waiting for parts.
I was on the road to reassembly, that is all the parts are her, and the timing belt was to be the first (and deepest) project to complete. I followed the VADIS procedure where you rotate the crank 90 degrees past the timing mark, then rotate it CCW back to the marks, to unload the springs in the cam sprockets. (at least, SO I thought) So far, so good.
I loosened the bolt in the center of the tensioner, used a hex-key to back off the tension, then slipped the belt off the waterpump and tensioner. when I slipped it off the exhaust cam, damned if the sprocket didn't jump about a tooth and one-half backwards (CCW)
So, my question is: Can I rotate the cam gear back to it's correct position without disturbing the location of the cam, or do I have to get a tool for locking the cams, including having to remove the cam cover (and all the attendant hardware). I really did NOT expect the exhaust cam to move when I slipped the belt off

Post by **JimBee** » 14 Jun 2012, 22:01

This happened to me the first time I changed a timing belt on the 850. I made a stick with a couple of long 1/4" bolts to leverage the cam sprockets and just turned it back. Assuming your crankshaft is aligned on the timing mark and your cam sprockets were properly aligned with their tiny, barely visible marks pointing into the V-notches on the belt cover, then you just need to return your cam sprocket to its correct position. If it keeps slipping off the high points of the lobes, I wonder if your crankshaft is exactly on the correct timing point. You have to make sure it is. When I bought my first 850 the exhaust was stinky. Much later, when I changed the belt, I found the exhaust cam was off a tooth (late, I think). So they can be off and still run.
If your sure of the crankshaft position, then thread the timing belt up and around to the intake sprocket. This is where you need your lever (stick with 3 inch bolts or whatever) b/c you'll want to be able to snug that intake sprocket CCW to pull out any slack on that side. Don't rotate so hard that you turn the crank, the belt should be just tight to the touch.

Then you'll slip the TB onto your exhaust sprocket and using your lever again snug that one until the TB is tight across the top between the 2 cam sprockets. At this point the belt must be tight from the crank up to the intake sprocket and across to the exhaust sprocket and the sprocket timing marks must point directly into the notches on the plastic cover.

If you're that far and your sure the crank hasn't moved, then just finish routing the belt and after a final check, you'll be ready to pull the pin.

Final note. When I'm sure my crankshaft timing mark is properly aligned, I used a short 6" level, place it vertically across the middle of my crank accessory belt pulley and using whiteout or a Sharpie marker if the pulley is clean, just scribe a vertical line that is exactly "plumb" on your level. Then you just look at that line or put your level back on it to check for movement of the crank.
You should also use a marker, whiteout, or something to mark the timing marks on the cam sprockets.
And, when you have the intake sprocket with the belt on and snug properly lined up, I suggest using a tiny vice grip to just "clothespin" the belt to the sprocket. This will hold it on while you work the TB onto the exhaust sprocket.

Good luck.

Dirtbag · Post by **Dirtbag** » 14 Jun 2012, 22:43

Thanks for the quick reply JimBee. Did your 850 have variable cam timing? This beast does. I'm not certain that the sprocket jumping back was the cam rolling off a lobe. (been there, done that) If it is just that, then your advice is precisely what I need to do. If it is the variable timing thing, and the sprocket backed off because of internal springs in the assembly, then I have to determine if I can crank it back in position (with a lever) without disturbing the position of the cam. If this thing had an inspection port that would expose a view of the exhaust cam, I'd be able to watch and see if the cam moved when finessing the sprocket back to time.
So, this begs a new question. Does the exhaust cam have springs and/or a sprague-type clutch built into the sprocket assembly? Or, perhaps a better question...how does that vct system work? What does what?

Dirtbag · Post by **Dirtbag** » 14 Jun 2012, 22:54

JimBee, forgot to mention, I did have the foresight to highlight the timing marks on the cams. That was the blur I saw when the belt popped off. Duh. I've had cams move when the lobes are just so, but in those cases, there was no vct issue AND the cams were visible. The other timing marks were and still are spot-on. I will use your plumb-line trick on the timing gear end, as the accessory pulley is off. i will also use your "clothes-pin" trick. I can see where the belt would be difficult to keep in place, especially if a cam is trying to twist out from under it.
Do these engines (S80 turbo) have bearing hold downs under the cam cover, or is the cam cover the only thing that keeps the cams in the bearing journals in the head?
Thanks again for the reply

Dirtbag454 · Post by **Dirtbag454** » 15 Jun 2012, 17:30

OK, a glitch in my cookies caused me to inadvertently re-register as "dirtbag" rather than "dirtbag454". Doh!
The post covering "Setting S80 VVT" sums up this experience. I will post the results of my folly as they occur.

Post by **JimBee** » 15 Jun 2012, 20:55

Hope you got this figured out. I have no experience with the VCT system, but if that's what you have I can see it would be tricky. I'd be on the phone picking up whatever hints I could from a Volvo tech (in Mpls. they will answer questions). In fact, you could call Borton Volvo from anywhere I suppose and ask a tech the question. They usually go through a middle guy and when the tech has a minute they'll ask while you're on the phone.

Good luck.

Dirtbag454 · Post by **Dirtbag454** » 16 Jun 2012, 00:58

Thanks JimBee. I grabbed the exhaust sprocket and turned it by hand back to the correct position. It sprung back to it's current position as soon as I let go. I am pretty confident that I can run the belt around the crank, idler, intake and exhaust cams, securing it gently with the needle-nose vice-grips (great suggestion, btw), and finishing the job on the waterpump and the tensioner. I may fire it up without the Aux belt or the cam tower cover so I can observe the belt. I'm all excited that this project may eventually be finished! I'll keep all posted as I plod and stumble to completion.

Dirtbag454 · Post by **Dirtbag454** » 19 Jun 2012, 03:32

Well, it's late, it's dark, and it's done. I'll wait till tomorrow to fire it up, still have to add coolant as I changed the water pump and thermostat. What a PITA! I fooled around for about an hour and a half, trying to get the belt over the tensioner, or the waterpump. I finally gave up on that approach and decided the last loop would be the exhaust cam because A) I could see it, and B) I could see it. Went on first try. VADIS wants to see crank, idler, intake cam, exhaust cam, water pump, and finally, tensioner. Great if you have tiny little hands and are already blind and used to working on stuff you can't see.
The springy sprocket on the exhaust wasn't a problem too much. I knocked the cams out of time a couple times, but the crank never moved. finally got all the marks lined up where they belonged with the belt on and the tensioner tensioned. Two rotations and the timing marks came up exactly wherre they were supposed to. We'll see how it runs after I put the coolant in. What a PITA.

Dirtbag454 · Post by **Dirtbag454** » 19 Jun 2012, 20:09

Well, it runs! Haven't had it on the road because I'm doing the control arm bushings now, and it has minimal ground clearance, plus, there is no place to hang the wheels. I was going to forego the cv boots,but noticed that I tore one (it was marginal anyhow) so now I HAVE to do that axle. This is the right hand axle, and the removal procedure doesn't seem to be the same as the left axle. How DOES one remove that axle from the transmission? Any VADIS procedures? Please?
Dave

Post by **Pauloil** » 19 Jun 2012, 21:39

pull it out and push the new one in.