I have this vehicle and it's running on only three cylinders. No 2 is out (ie, second from flywheel, I believe that's how Renault count!) I replaced the coil packs with no joy, and on changing the plugs I found small shards of metal and a bit of oil on the no 2 plug. I've carried out a compression test and sure enough No 2 is very low. It doesn't increase with a few squirts of oil so I'm assuming the rings are ok and I'm looking at either a head gasket or a burnt valve/seat. The vehicle has only done 28k miles so I'm surprised at all this. Anyone here with experience of these motors? Would a failed gasket introduce metallic shards into the pot? Or is this guaranteed to be more serious? I intend to do this work myself, so info on anything unusual to be expected would be most gratefully received. I'm led to believe that the cam belts are a bit tricky to tension properly.
Renault Scenic 2000 1.6 16 Valve Petrol
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It sounds like hell, but I guess that a valve has hit the piston recently, if there are bits of metal visible.....a blown head gasket wouldn't introduce metallic particles.
Whats the history of the engine?
John
Whats the history of the engine?
John
The history is one carefullish owner from new, never been thrashed and genuine mileage. (I've known it from new) It's not like there was a load of material in there, I've been running it for a while since doing the plugs, and when I did the comp.test at the weekend just gone there was a bit of oil on the plug, but no more metal. And there was only a tiny bit in the first instance, although I realise any at all isn't great! My instincts thought it might be the oil ring on the piston, but comp. test suggests it's top end.
The only way for ring material to get up there is due to severe piston damage. I see a fair bit of this with two stoke chainsaw motors etc, where the piston has seized to some degree.
The oil control ring, if there is one, is at the bottom of the piston anyway.
So, the shards of metal......I would have thought that these would be aluminium from the piston crown (can you test them with a magnet?)
Valves bend merrily, and the heads sometimes snap clean off...nothing else.
The head has to come off I'm afraid.....as for the timing belt, the engine does need to be locked when replacing the belt and I would guess that there has been some recent work in that area.
Any comment?
John
The oil control ring, if there is one, is at the bottom of the piston anyway.
So, the shards of metal......I would have thought that these would be aluminium from the piston crown (can you test them with a magnet?)
Valves bend merrily, and the heads sometimes snap clean off...nothing else.
The head has to come off I'm afraid.....as for the timing belt, the engine does need to be locked when replacing the belt and I would guess that there has been some recent work in that area.
Any comment?
John
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Fair enough - it was the presence of oil rather than the shards that made me suspect the oil ring. Am I wrong in thinking that if a valve had bent it wouldn't fully close, and this might lead to a clattering as the follower hit it? I'm not hearing any unusual sounds while running the engine. I think I binned the shards - it was a while ago I changed the plugs. I might still have the plugs, maybe the one in question might have something left on it. I'll dig them out.
Not sure what you mean here? It had a new timing belt done by Renault at the appropriate interval a few years ago. But it's run fine since then until recently. No other work has been done. Hence the mystery! Thanks for your input.
The head has to come off I'm afraid.....as for the timing belt, the engine does need to be locked when replacing the belt and I would guess that there has been some recent work in that area.
Any comment?
John
Not sure what you mean here? It had a new timing belt done by Renault at the appropriate interval a few years ago. But it's run fine since then until recently. No other work has been done. Hence the mystery! Thanks for your input.
Any cylinder that isn't firing will show oil traces on its plug....its a bit of a red herring, that one......!
I think I'd try two things.....could the spark plug threads be stripped? (Shard evidence)
Take the timing belt top cover off and slowly rotate the engine - looking for belt teeth that are no longer there.
I'm also wondering if some other metallic foreign body could have been ingested by the engine - I don't know if Renault have used inlet tract 'butterflies' on this motor.
Either way, that cylinder is down on compression - so its head off, I guess.
John
I think I'd try two things.....could the spark plug threads be stripped? (Shard evidence)
Take the timing belt top cover off and slowly rotate the engine - looking for belt teeth that are no longer there.
I'm also wondering if some other metallic foreign body could have been ingested by the engine - I don't know if Renault have used inlet tract 'butterflies' on this motor.
Either way, that cylinder is down on compression - so its head off, I guess.
John
Yeah, I realise the head's got to come off. I'll let everyone know what that reveals, although it won't be for a few weeks. I'd bet that the plug threads are fine by the way the compression tester and plugs screwed in, even though they are too deeply recessed to see anything. The car's immaculate otherwise, so I'm quite keen to sort it and get a few years out of it. Thanks Burnerman.
We'd appreciate the update....if you decide to go ahead with the work, you'll need a head gasket set, timing belt and new head bolts - and it would be a good idea to replace the water pump too.
John
John
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