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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 20384
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My wife has a Renault megane 1.9 diesel turbo and too much

Resolved Question:

My wife has a Renault megane 1.9 diesel turbo and too much oil was put in by the initial appointed garage ( approx 7.5 litres measured when taken out in total) when it required only 4.5 litres .and they drove it back to me when the car broke down and was blowing out smoke apparently and stopped running the garage claimed that the car just required a new Turbohowever the car was perfect before the service ,and there was nothing wrong with it .It is now with another garage being investigated and will now not start and on cranking is making a knocking noise I was advised by the first garage that" it had been running on its own oil and they sent a message with the breakdown truck and advised the new garage "not to try starting it "for this reason ?????
.Can you please advise as WE didnt put the oil in .It was put in by the garage on service and had been working perfectly well before it was picked up by them .???? It just required a service and MOT (which it passed its Emmissions test and failed the rear disk brakes) that was carried out before the service.
Please help with your advice Thank you Lloyd Rakusen
Submitted: 4 months ago.
Category: Car
Expert:  Shantal-Mod replied 4 months ago.
I'm Shantal and I'm a moderator for this topic.
I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.
I was checking to see if you had already found your answer or if you still need assistance from one of the Professionals.
Please let me know if you wish to continue waiting or if you would like for us to close your question?
Thank you,
Customer: replied 4 months ago.
Dear Shantal,
I do believe I instigated a payment to you for what seemed to be a straight forward question from your acclaimed professional mechanics .?
What do you suggest that I do now ?
This is a matter of extreme importance please answer me by return as I want to approach a legal company for further advice.
Thank you *****
Customer: replied 4 months ago.
I do think 24 hours is too much although I appreciate your advise and integrity in this matter I am under a time constraint .!!
Expert:  Matt replied 4 months ago.


its likely that the combustion chambers are full of oil

I'd suggest to remove the glow plugs and wind the engine over on the starter with some rags in front of the holes to catch what comes out, clean the glow plug tips with some solvent / brake cleaner and then try again

what can happen is it runs off its own oil and this can lead to 'runaway' where the engine revs uncontrollably and can then be damaged by over-speeding

so if this starts be prepared to try and stall the engine by dropping it into gear

Customer: replied 3 months ago.
I understand your comment however we think the damage has already been done and ...what damage in your opinion do you think has been done to the engine ...There is a knocking noise when cranking the engine??
Please read my initial brief to you again and give me a diagnosis from your personal unbiased professional opinion
ThanksLloyd ***********
Expert:  Matt replied 3 months ago.

Hello Lloyd

the worst case for the knocking could be as bad as a worn big end shell and in which case the engine will have to come apart to replace bearing shells and re-grind the crank

and often this can run to several hundred pounds in parts and machining charges so it can be more economic to replace the whole engine with a good used unit


it may not be this bad and the knocking could just be a lot of pre-ignition due to the oil in the chamber

Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 20384
Experience: BEng hons Mech engineering, in auto industry 22 years
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