Garage ruined engine when car took in for MOT

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  • sartois
    sartois Posts: 162 Forumite
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    Aylesbury_Duck wrote: »
    There's the problem. They're better when they're made from sticks, and better still from bricks. Then when the engine huffs and puffs, it doesn't fall apart.

    I see what you did there ;)
  • sartois
    sartois Posts: 162 Forumite
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    AdrianC wrote: »
    OK - Are you familiar with the basics of valves and pistons, and the four-stroke engine? Suck-squeeze-bang-blow...
    4_Stroke_Engine.gif

    Except it's all going round much faster - even at idle, the crank is going round 15 times a second, while at full revs, that's 75 times a second on a diesel, 100 or more on a petrol. You've got two powerful explosions on each of those revolutions...

    The camshafts operate the valves - at the top. The crankshaft is connected to the pistons (going up and down). The two are tied together, in a precise relationship. If they drift much outside that, bits meet each other, and it gets VERY messy internally.

    It always used to be gears or chains - but it moved to rubber belts, because they were quieter and more efficient. But belts need changing regularly, because they age in the heat of an engine, very rapidly if they get oil on them.

    So manufacturers are going back to chains. But because they're also trying to increase efficiencies, they don't always last the full life of the engine, like they used to, especially if oil changes have been neglected. They usually give audible warning of stretching - through funny noises - but not always, and those noises aren't always heeded...

    Actually no wasn't familiar at all :) Not my field. I've learnt far more than I thought I would today!
  • AdrianC
    AdrianC Posts: 42,189 Forumite
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    So - diesel runaway... Diesels don't have a sparkplug. They use the heat generated by compressing the air to ignite the fuel.

    Diesel fuel isn't very different to oil.
    If the seals on a turbocharger get hard, they can leak oil past, into the air going into the engine. If there's a lot of oil gets in, then the engine can start to burn it instead of fuel.

    Diesels are "controlled" by varying the amount of fuel injected - more, they speed up, less, they slow down. Stop injecting, they stop.

    Except... If the engine's running on that oil, they can't be easily stopped. And if there's as much oil as they want, they'll just keep speeding up. And speeding up. Until they can't speed up any more. Then they'll run and run and run until there's no more fuel. And the fuel is the engine oil. So you've got a very, very fast-running and hot engine that's suddenly got no oil.

    The official workshop procedure for most manufacturers for dealing with a runaway... Evacuate the workshop and wait for the big bang then the smoke to clear. Seriously.
  • angrycrow
    angrycrow Posts: 1,078 Forumite
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    AdrianC wrote: »
    So - diesel runaway... Diesels don't have a sparkplug. They use the heat generated by compressing the air to ignite the fuel.

    Diesel fuel isn't very different to oil.
    If the seals on a turbocharger get hard, they can leak oil past, into the air going into the engine. If there's a lot of oil gets in, then the engine can start to burn it instead of fuel.

    Diesels are "controlled" by varying the amount of fuel injected - more, they speed up, less, they slow down. Stop injecting, they stop.

    Except... If the engine's running on that oil, they can't be easily stopped. And if there's as much oil as they want, they'll just keep speeding up. And speeding up. Until they can't speed up any more. Then they'll run and run and run until there's no more fuel. And the fuel is the engine oil. So you've got a very, very fast-running and hot engine that's suddenly got no oil.

    The official workshop procedure for most manufacturers for dealing with a runaway... Evacuate the workshop and wait for the big bang then the smoke to clear. Seriously.

    No the correct response to a run away engine is jump in the car, clutch in brakes on engage a high gear and dump the clutch to stall it. Any garage letting it deliberately run to destruction is being negligent.
  • forgotmyname
    forgotmyname Posts: 32,552 Forumite
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    When the revs build its often too late, it can quite easily overpower the clutches grip. If you catch it early then yes brakes and clutch to stall it.

    Or stuff a rag in the intake to starve it of air.


    Is it just me or is that animated engine picture relaxing and mesmerising?
    Censorship Reigns Supreme in Troll City...

  • Strider590
    Strider590 Posts: 11,874 Forumite
    edited 18 May 2017 at 6:08PM
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    My money is on a failed radiator fan, driver wouldn't necessarily notice it if they keep moving, might get a bit warm, but driver probably doesn't look at the dash that much.


    That now said, was this car anything sporty? I ask because I stopped using a local garage when I saw their technicians taking customer cars for a "spin", and later heard from a friend that he took his car for MOT, walked home and was promptly surprised to see his Clio sport 182 being driven past him at break neck speeds.
    “I may not agree with you, but I will defend to the death your right to make an a** of yourself.”

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  • Mercdriver
    Mercdriver Posts: 3,898 Forumite
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    Strider590 wrote: »

    That now said, was this car anything sporty? I ask because I stopped using a local garage when I saw their technicians taking customer cars for a "spin", and later heard from a friend that he took his car for MOT, walked home and was promptly surprised to see his Clio sport 182 being driven past him at break neck speeds.

    Come on. This is a Fiat 500 diesel. How sporty do you think it's likely to be?
  • Strider590
    Strider590 Posts: 11,874 Forumite
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    Mercdriver wrote: »
    Come on. This is a Fiat 500 diesel. How sporty do you think it's likely to be?

    It ain't about the engine, it's about how it looks.
    “I may not agree with you, but I will defend to the death your right to make an a** of yourself.”

    <><><><><><><><><<><><><><><><><><><><><><> Don't forget to like and subscribe \/ \/ \/
  • DTDfanBoy
    DTDfanBoy Posts: 1,704 Forumite
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    Strider590 wrote: »
    It ain't about the engine, it's about how it looks.

    Have you ever seen a Fiat 500 :eek:
  • facade
    facade Posts: 7,030 Forumite
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    edited 18 May 2017 at 7:38PM
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    DTDfanBoy wrote: »
    Have you ever seen a Fiat 500 :eek:

    This is a proper Fiat 500
    https://commons.wikimedia.org/wiki/File:Fiat_500_Topolino_-_Flickr_-_exfordy.jpg

    Although I believe they have since released a facelift version
    https://commons.wikimedia.org/wiki/File:Fiat_500_Abarth_(Foto_Sp_2016-06-05).JPG?uselang=en-gb

    File:Fiat_500_Topolino_-_Flickr_-_exfordy.jpg
    I want to go back to The Olden Days, when every single thing that I can think of was better.....

    (except air quality and Medical Science ;))
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