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Discussion Starter · #1 ·
Scenario:
  • the sidewall (ring) of the exhaust camshaft sprocket came off and wrapped itself round the sprocket under the belt
  • the belt didn’t break, but the camshaft notches at flywheel end are no longer aligned
  • I’ve removed the timing belt and am just trying to gauge whether the cams are behaving as they should (by turning them very gently and not very far)
  • plugs are still in and the inlet cam is quite stiff to turn
  • but the exhaust cam turns very freely and smoothly
  • is this normal?

Thanks!
 

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Discussion Starter · #3 ·
They are the original Renault sprockets and each has a ring spot welded to the outer side of the sprocket, acting as guides / retainers to keep the belt in place. The exhaust cam ring detached and got crushed between the belt and the sprocket.
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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Ah ok. In that case, imo you have bad news especially mentioning the misalignment of the shaft notches ............ you should not be able to rotate the camshaft by more than about 10 degrees without encountering major resistance - you should not be able to complete a full rotation by hand using the pulley for example and if you try to using a spanner etc you will be able to feel every cylinder's cam lobe actively engaging the valve

Suspect head/valve damage - confirm by doing a proper timing belt alignment and then doing a compression test on all 4 cylinders.

More importantly I think is why that ring came off in the first place - just Murphy and bad luck? - or did the belt start wandering because of a pulley/tensioner misalignment/misadjustment/failure
 

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Discussion Starter · #6 ·
Thanks. My concern about doing a compression test is that I may cause even more damage by running the engine? e.g. if some exhaust valves are stuck in their downward positions they may damage the pistons or snap off completely…
So I’m wondering… if I remove the plugs and go in with an endoscope camera, maybe I’ll be able to see what’s afoot.
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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If you have an endoscope its possible to see yes ............... it's also why I suggested doing a proper cambelt timing job first
 

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Discussion Starter · #8 ·
Forgive my ignorance, but presumably there is a point in the crankshaft’s cycle, where all pistons are at the same level as each other and all will be far enough down in the cylinders that I can feel free to turn the camshafts without the valves and pistons touching?
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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You are right, but then I misunderstood your "freely" description - I thought you meant without resistance at all.

If you want to do complete camshaft turns with all the pistons in mid travel, then its plugs out, long stick/screwdriver in any plug hole and see what is mid travel
 

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Discussion Starter · #10 ·
No, you didn’t misunderstand. I did mean that the exhaust cam spins freely with no resistance, which suggests to me that there are no valves present! i.e. they are all bent and stuck down such that they don’t return upwards and don’t push back on the cam lobes.
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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Aaaaah ..............in that case my deepest condolences :eek:
 

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Discussion Starter · #12 ·
Thanks for all your feedback!
Quick question on using Partsouq… what does it mean if a part is numbered in a diagram but is not listed to the left? Does it mean Renault no longer supply it? e.g. in the attached, the sprockets are identified in the diagram as item 2, but don’t appear in the list.
Product Rectangle Font Screenshot Parallel
 

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Technical Supremo.
Scenic II, 2004, K4MW761, DPO
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Sorry man - I don't know what their convention is.

However I do have other reference material and the exhaust sprocket #2 is listed as having part number 8200020968 and 2 x 8200718048
 

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Super Moderator Technical Supremo Platinum Member
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If you take the rocker cover off and inspect the lobes as you turn cams (piston mid stroke) you should be able to see lobes and valves/springs and get an idea if moving or not.
 

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Discussion Starter · #20 ·
So have rebuilt the top-end and set the timing. Now putting everything back on.
Am fitting new tensioner and idler pulleys for the auxiliary Micro-v belt and can’t find any torque wrench settings in the Haynes manual or on-line.
Anyone know the torque wrench settings for these two pulleys?
Thanks in advance.
 
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