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Discussion Starter #1
The Lag2 big ends failed at 94k miles. It had been run on Mobil1 synthetic for its whole life, with 18k oil changes.
One bearing shell was welded to the crank, another in the sump. Oddly, the knocking sound from the engine came from the top-end, and didn't vary with ,load. Turns out the noise was the piston hitting the cylinder head. The remaining big end shells show signs of cracking/de-lamination of the white-metal. So I suspect the cause was fatigue failure of the bearing surface, not lack of lubrication or wear. Renault UK response was "we have no known issues with any parts on DCI engines, at any time".... total denial.

Have we got any bearing experts to comment on the photo ?
 

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Artful Bodger..chief sneaky eliminator
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Sorry, not an bearing expert but I note that you had religious correct oil changes as specified by Renault at 18k miles but I do think that should be a warning to all to reduce these changes to 9k or 12k.

My own Scenic 1.9, last years model states 18k/2 years whatever comes first but having seen the unfortunate damage to your car only strengthens my opinion on this.

Hope you get it sorted but it is not going to be cheap sorry to say.
 

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Anyone who runs a Dci engine on 18K service intervals is crazy.:crazy: It is well known in the motor trade that this is far too long and in fact on some models Renault have reduced the service intervals to 12K or each year whichever comes first.

The fact that one shell welded itself to the crank is a sure sign of poor oil pressure and the fatigued shell damage could have been caused by the shock from the piston striking the cylinder head. Also pitting can be caused by oil contamination such as water, acids, etc., When it comes to contamination a good quality oil may not help.

Also has the oil pump pressure release valve been checked.:)
 

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Discussion Starter #4
Costs of the repair(so far) are: crank regrind/bearings 拢160, bolts/belts/gaskets 拢140, s/h conrod 拢20. I really want to fit a new oil pump, but Renault want a ridiculous 拢170 for a new one:mad:.
I suspect driving-style may contribute to BE failure too. Dualmass flywheels may hide vibration when the engine is labouring. Tall gearing doesnt help. Presumably Renault will eventually fit impoved bearings like other diesels....
http://www.mahle.com/C12570B3006C0D49/CurrentBaseLink/W26TFGD7115MARSEN
 

Technical Supremo, Platinum Member
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The oil pump to me is a no brainer, the bearing welded to the crank is very likely lubrication failure so suspect oil pump and its drive, oil pressure relief valve, clean and blow out all oil ways.
I would have a real good look at the oil system, not too could be expensive.
 

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I would agree Ralph - not replacing the oil pump is akin to transplanting a dicky heart into a human being. It's not if it going to fail it's a question of when.:)
 

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Discussion Starter #7
The car is running again, using a second hand oilpump. Saab, Fiat Volvo etc. all have vehicles with 18k oil changes, and their engines survive beyond 100k miles (mostly!). Note that my engine did not suffer from lube failure, mains were all in good condition, no signs of bearings over-heating. So it looks like normal wear can kill the big ends by 94k miles. I see there is another 2005 Laguna DCI on Ebay today with B/E failure at 104k miles (yours for 拢700 in Wantage).
 
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