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Old 02-18-2023, 03:51 AM   #1
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Cylinder 3-6 Cams Jumped Timing

Hi guys,

Long time lurker and always appreciative of the advice I get from this forum.

I have a 2004 986 2.7 RHD, 3 chain engine with 127,000 miles. I'm based in the UK, if that makes any difference.

My car was over-fuelling due to an exhaust leak in one of my cats. But seeing as I was going this far and faced with an alignment after removing the braces, I thought I'd keep going and do my juddery clutch, slack flywheel, RMS (I have a nasty leak) and probably the IMS (if I felt brave enough).

A friend of mine came over to give me a hand with getting the gearbox out and we stripped the clutch down to the flywheel. Unfortunately he rotated the crank using the flywheel bolts (totally the wrong direction for trying to undo the bolts, I would add, durr) and it's messed up the timing of Bank 2. His actions were associated with three clangs, which I'm pretty sure was the chain jumping on the IMS sprocket. All three tensioners were in place and untouched.

I've pulled all four caps from the camshaft ends and verified that the Bank 1 markers (front of engine) are bang on when the crank is at TDC. Bank 2 at the rear are consistently off of centre (to the left). I say consistently, both intake and exhaust are off by the same amount.

So I'm in a quandary of how to fix this. The engine does rotate via the 24mm crank pulley bolt, which is how I've verified that the timing is off. Didn't feel too difficult to move either, considering the spark plugs are in the car, so I don't think I've bent any valves.

Any help or advice would be massively appreciated, as I would love to have my car back on the road. I can take my time with it as I have another car, but I'm tight on space so the engine has to remain in the car.

Cheers!

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Old 02-18-2023, 08:44 AM   #2
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if you got lucky you can fix this in the car, reinstall the1-3 cam holder and the crankshaft pin, then remove t he 4-6 oil scavanger pump, loosen the 4 bolts holding t he cam gear in place and try to turn the cams from the other end to line up and if they do tighten the bolts on the cam gear. If you cannot get it close then you will have to remove the cam cover and rotate the cam gear to get the chain back in the right spot. you can download the 986 service manual to look up on how to accomplish that, but it can be done.
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Old 02-18-2023, 10:21 AM   #3
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Quote:
Originally Posted by harryrcb View Post
if you got lucky you can fix this in the car, reinstall the1-3 cam holder and the crankshaft pin, then remove t he 4-6 oil scavanger pump, loosen the 4 bolts holding t he cam gear in place and try to turn the cams from the other end to line up and if they do tighten the bolts on the cam gear. If you cannot get it close then you will have to remove the cam cover and rotate the cam gear to get the chain back in the right spot. you can download the 986 service manual to look up on how to accomplish that, but it can be done.
Thanks for the advice - very much appreciated!

Iíve been reading all day and I have a feeling that Iím going to have to lock Bank 1 and crank as you suggest, remove the tensioner on Bank 2 (which is a bit of a pig), then the cam cover to hopefully move the sprockets on the chain. Assuming thereís enough slack, of course. Thatís all I can think, at least.

Just to check Iím not being an idiot, the slots on the cams are definitely all supposed to be vertical when the engine is at TDC?
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Old 02-26-2023, 03:11 PM   #4
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Well this is proving to be a pig of a job!

Iíve got my cam timing tools now and have locked the two affected cams at, what would be, TDC. The valve cover is now off, which was pretty tough due to access.

My plan is to remove the Bank 2 tensioner to allow me to take off the exhaust sprocket, which will create enough slack to allow me to then feed the chain over the intake sprocket by three links. Which Iím planning to do by rotating the crank forward at the same time. Iíll know Iíve succeeded when the timing marks line up on Bank 1 and the crank locks at TDC.

Whatís really thrown me now is access to the Bank 2 tensioner. Itís ridiculous! My AC has been discharged for ages (bad leak under the car), so Iím going to try and remove the two feed lines and take the compressor out for access. On the three chain cars the position of the tensioner is different, so thereís a bracket holding a hard line to the power steering pump thatís blocking access to the tensioner.. That needs to come off, but the AC blocks that. The idea of messing with the power steering reservoirs puts me off, which is the official way of doing it, so seeing as my AC isnít pressured Iím taking a short cut.

Iím disappearing down a rabbit hole with no guarantee of success, but Iím persevering and writing up where I can in case this is useful reading to anyone in my predicament in the future.
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Old 02-26-2023, 04:55 PM   #5
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Fast forward to 12:33 see if this helps.

https://youtu.be/dyJ2KQyvaGA
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Old 02-26-2023, 08:30 PM   #6
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...and if anyhow possible, install the tensioner back to it's treads by hand so you'll feel that it really is goin to the threads. I have read couple of cases when the tensioners have been pushed to the thereads with ratchet or other tool and the threads on the aluminŪum block has been stripped... -> very expensive.
I just changed all 3 tensioiners to new and one had a hard time to go in to the threads due to compression needed when those are primed with oil.
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Old 03-14-2023, 02:34 PM   #7
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Another update on this one.

I had no choice regarding the Bank 2 tensioner in the end. The pressure line bracket for the power steering makes it impossible to access the tensioner. So out came the AC compressor, PS fluid drained from under the car, PS reservoir out and hardline (plus bracket) off. Oh, and letís not forget the intake pipe that had to come out to access the reservoir. Terrible design for access to this one component.

I then spotted that my timing for Bank 1 was also off for whatever reason, so I swore a lot, and off came the valve cover and cams removed in order to protect the valves whilst I rotated the engine to TDC. Not sure which TDC it is, but I guess it doesnít matter (Iím thinking that the spark is determined by the camshaft position sensor). So I now have all four cams removed (and labelled properly), and looking forward to a complete re-time.

I have since tackled the IMS and RMS - both went very smoothly. Although the tensioner for Bank 1 separated into two pieces when I removed it. I also found a 20mm x 8mm chunk of tan coloured chain tensioner guide sitting in the bottom of the chain housing when I took that valve cover off. So I reckon Iíve caught a problem before it caused a much bigger one! The chunk looks like the lip from the crank case side of the tensioner guide. So thatís going to be replaced, too.

So Iím on the rebuild now and looking forward to driving the car, not laying underneath it. Certainly learned a lot about these engines in the process though!
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Old 03-14-2023, 09:25 PM   #8
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Since you have the engine this much apart, change all 4 cam chain remps and also all 4 IMS-to-cams chain ramps at the same time. Those parts are cheap and can cause major engine damage if one of those break...
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Old 03-15-2023, 06:13 AM   #9
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Not sure that this applies to your engine, but you should check this out.
Failed (mushroomed) lifters on M96 engines?

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camshaft deviation , ims , timing


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