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Renault Clio Mk2 1.2 8v - Cambelt Problem

My W reg bangernomics Renault Clio stopped running and was diagnosed by a mobile mechanic (I was away with work) as having no compression and probable stripped cam belt due to oil contamination from a weeping rocker box cover.

Seemed plauasible, if a little odd but there's definitely a spark and fuel so compression must be the missing ingredient. (CPS and coil pack replaced).

One top end strip later I have a perfectly dry and intact cam belt but clear evidence that valves and piston have touched.

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No obvious damage to the head but I can see on both the valve edge and piston where they've kissed.
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Turning the engine by hand before I stripped it there was definite resistance around TDC - to the point I would have needed to use force to get past it - say the sort of force that a starter motor could exert...

I didn't check that the timing marks were correctly aligned before stripping (my oversight) although I wasn't keen on forcing it by hand (spanner).

I can source the necessary gaskets and straight valves fairly cheaply but I would be keen to understand why the valves and pistons started to argue about who should be where when before I fix what may only be the symptom of a greater malaise.

Not sure if this a smoking gun, but the crank pulley bolt (for PAS pump and alternator) was loose but cambelt pulley seems fine (I've not removed it yet - the Haynes manual indicates its keyed and not a taper).

It ran perfectly well for over a year in my hands before it broke - it has had a top end rebuild as a result of a broken cambelt some (~8) years ago (according to the receipts).

I do drive it fairly hard but it failed waiting at some traffic lights. I managed to restart it (hot) and drove the three miles home but very down on power and then it refused to restart when cold - hence the diagnosis and strip.

Incidentally, my fault reader doesn't fit the OBD port, it seems as if the lug on the car's connector is too big - is this a normal Renault thing?

Can a belt stretch or become elastic enough for the timing to slip to cause bent valves?

Anyway, what guesses/experience for the cause of my valve train problem?

Reply to
sweller
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The crank sprocket is not keyed, correct cleaning and tightening is essential. Most likely this step was wrongly done when the belt was fitted.

The belt should have been replaced about three years ago (5 years max in the UK IIRC) Which would have saved the engine from this unnecessary rebuild.

Reply to
MrCheerful

Pre 97 they used a special rectangular connector.

No.

Loose crank sprocket.

Reply to
MrCheerful

Aha! What is the correct tightening method as the Haynes manual says nothing about pullers to remove it and replacement is simply "ensure the lug on the sprocket engages with the cut-out".

How do I make sure it's correctly timed if there's no key?

The belt hasn't broken - but something has moved. It's a banger, there's always something unnecessary going on!

Thanks.

Reply to
sweller

the crank is timed with a pin in the flywheel. the sprocket and crank must be degreased, the crank sprocket has a mark which must align with the notch below it, the new crank bolt is tightened to 40nm plus 70 degrees. use the cam sprocket mark on the sprocket web with 'E1 E3' written on it aligned with the notch at the top. Align the belt markings with the cam and crank sprocket marks.

Never believe anything important written in the 'Haynes Book of Lies'

Reply to
MrCheerful

I've had it all apart and it looks as if the t's not keyed in the hardened steel key piece manner but simply using cast lug on the sprocket.

Which seems to have sheared off on my sprocket:

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It's not on a taper either but worryingly the crank end is damaged - I need to look at a new sprocket and see if it will locate well enough on the remains of the cut out:
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Or is the crank scrap?

I think I may have got lucky with the valves as they all seem to close with the rockers removed:

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Now, where will I get a new/good used sprocket?

Reply to
sweller

Must be a different 1.2 to the one I looked up, they do list about 10 variations.

It should be possible to order a new sprocket, the crank looks like it will be fine, just clean up any raised metal so that the new sprocket can slide on, if the sprocket is correctly tightened all will be good, the keyway will not be under any stress if the bolt is tight.

Put the plugs back in the head and fill the combustion chambers with petrol, any leakage past the valves will show very quickly.

Reply to
MrCheerful

Or pour a bit down each port when the valve is shut. Maybe safer to spray something less flammable like WD40.

Reply to
Peter Hill

even safer to use an air powered valve leakage detector :)

Reply to
MrCheerful

Is it possible that the valve stems could be bent slightly so that they stick a bit and don't slide up and down smoothly?

Reply to
rp

Rarely, usually any bend just prevents them closing, the clearances in the guides is quite small, so any bend at all is too much. You also can find that the guides are cracked from the sideways forces.

Reply to
MrCheerful

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