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Second time a valve broke, any idea what could have caused this?

Discussion in 'Problems, Fixes, Tips...' started by Ewoud van Munster, Aug 1, 2017.

  1. Ewoud van Munster

    Ewoud van Munster Copenworld Newbie

    Aug 5, 2015
    Delft (netherlands
    Daihatsu copen 0.7
    Hi all,

    First of all, let me introduce myself shortly,
    I'm Ewoud, 23, and the proud owner of a 0.7L copen for a few years now.
    I live in the Netherlands, and use my car as a student for all kinds of trips/ holidays/ work, but mainly, chilling and drive without roof:)

    However, i have some engine troubles...

    In april 2017, i have had a complete compression loss in cilinder 3.
    The spark plug was broken, and both the curved bottem part which creates the spark as the 3cm "nail" part inside the sparkplug were broken, and missing.
    This resulted in a broken exhaust valves, and a broken turbo.

    We have replaced both the exhaust valves of the 3 cilinder(including oil seals), and the turbo.
    Everything was fine, compression was 10.4 ; 10.2; 10.8 ; 10.6, and in runed smoothly.

    Now the sad part, a few weeks ago in south of france, the third cilinder broke again after approx 1000km.. :(
    no compression, and after we (again) took the engine apart, we saw the same problem, a broken valve:

    We can repair the valve again, but I don;t know what the underlaying problem is, that causes the valve to break.

    Does anyone of you have any idea, what could cause the second time for the valve to break?

    Kinds/regards, Ewoud

    Attached Files:

    Last edited: Aug 1, 2017
  2. jez77

    jez77 Copenworld Regular

    Jan 16, 2015
    Brisbane Australia
    2003 Daihatsu Copen
    2000 Toyota RAV4
    Am I right in thinking it is a different valve to last time?
    Is the valve moving freely when you turn the cam?
    Any scoring on the cam lobe?
    Can you see any marks on the piston where it had hit?

    FYI, I'd remove those burrs off the cylinder head. They can cause hot spots that can cause detonating.
  3. welz

    welz Copenworld Regular

    Jun 8, 2015
    Leverkusen, Germany
    copen 2003
    i`d never seen this before after refubish again . Are you sure ,you had search and found everything from the plug rest in the engine?

    I'd remove those burrs off the cylinder head, too..ever... but hardly to repair..little things in oil pan..etc.
    Last edited: Aug 2, 2017

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