anyone help with engine fault diagnosis?

Discussion in 'General Motoring' started by Chris B, Apr 30, 2004.

  1. Chris B

    Chris B Guest

    OK, just before I finally buy a new engine or get mine fully reconditioned..
    does anybody have a clue as to what these symptoms might indicate?

    It's a fuel injected 1.9 litre XU block, by the way. I'll give you the full
    list of symptoms since I first noticed the problem.

    First off... last year sometime. I got stuck in traffic for a long time with
    the engine idling and I had blue smoke out the back for about ten miles
    afterwards - so it was burning oil. Figured it was making it's way down the
    valve stems or something. This only seemed a problem when left at idle for a
    long time.
    Second, it starts consuming oil at increasing rates. I don't notice any blue
    smoke though except when left idling as before. Begins to look like it may
    be leaking a bit of oil out of the engine somewhere, but I'll be damned if I
    can see where.
    By the start of this year, it's still using up oil and now I'm hearing a
    ticking noise when I start the car up, coming from the top end on the
    opposite side to the distributor. It's not too loud and goes away after a
    couple of minutes driving.
    Next, I think I started smelling petrol pretty badly whenever I stop
    anywhere. It seems to be coming out with the exhaust gases, but it's never
    backfired (so maybe not?).
    Over the past couple of months, the ticking noise has worsened. I also had a
    rather bad fright when I managed to pour 2.5 litres of oil into it about
    three weeks ago before it was up at the maximum (quite a sudden drop,
    although I didn't note the miles - possibly around 1000). Next, I drove it
    maybe 50-60 miles and the ticking noise got quieter, but didn't actually go
    away all through the journey.
    Now, it's ticking very loudly. It's been three or four weeks ago since I
    last put oil in it, but the oil level won't budge from the maximum - so it's
    stopped consuming oil??!? Sounds like maybe the oil isn't getting to the
    head? What's likely to happen? Loud explosions?!?

    And yes, I understand that all this probably means 'shagged engine', but
    it'd be cool if I actually knew what was causing all this before I get it
    reconditioned.. might be better off scrapping it and looking for another
    engine if this is *really* serious.

    Cheers,

    Chris.
     
    Chris B, Apr 30, 2004
    #1
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  2. Chris B

    G.T Guest

    Hi Chris,
    Would indicate problem with cylinders 3 or 4 (cyl.1 is on the flywheel
    side).
    Ticking noise may be caused by a bad valve clearance, you may need to check
    it. My second idea would be a worn camshaft, as the very first XUs (up to
    1984 or 1986, I don't know) were prone to "fast" camshaft usage, but AFAIK
    the replacement camshafts always cured the problem.
    Still, could indicate either a wrong valve clearance &/or worn camshaft.
    Strange, I've never heard of an engine which would burn oil (moreover, at
    high rate) and would suddenly stop burning oil. BTW, did you make an oil
    change before it stops burning oil ? Perhaps you changed oil grade for a
    thicker one ?
    No (at least if I get your question the way it should), usually causes bad
    firing, 'cause oil is far harder to burn than petrol.
    Of course. Also check compressions if possible, then report to Pug's values
    for a diagnostic / todo list. I mean, I have no clue about the point you may
    need to work about compressions, but for example the 205 Diesel tech manual
    I have here says "don't go for an engine servicing or overhauling before
    having controlled air filter, valve clearance & starter speed if compression
    test reports under 18 bars".
    This value of 18 bars could be called "critical compression value" or
    similar (my term, not sure it's a usual one), of course is lower on a XU,
    perhaps doesn't exist.

    BTW, valve stems is known to be a "potential weakness" of XU engines, watch
    out old 405s for example.

    So, my conclusion is :
    - valve clearance,
    - camshaft / possible worn cam,
    - no clue for the burning / not burning oil. Perhaps it was leaking from
    the back of camshaft cover (where you don't see that well).
     
    G.T, May 1, 2004
    #2
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  3. Chris B

    Chris B Guest

    Thanks for the advice. I've been convincing myself for a long time now that
    the engine is in a seriously bad state, yet it keeps on going. I'll check
    the valve clearances - maybe it isn't as bad as I've been thinking. I've
    heard about the valve stems being a potential weakness, and I do think some
    oil is being burnt from there. I just can't understand why it's stopped
    burning/leaking as I've been using the same oil. My only clue is that up
    until last month, I was covering more miles on the motorway on a daily
    basis. Now, I'm doing more short journeys in town so maybe it's just the
    effect of less miles and lower speeds - perhaps it starts burning oil up at
    high revs? Does that sound likely?

    Cheers,

    Chris.
     
    Chris B, May 1, 2004
    #3
  4. Chris B

    G.T Guest

    Hello,
    I guess it's quite certain.
    Worthes a try, for that you only need to remove the camshaft cover, complete
    valve clearance checking takes, say, 1 hour. Setting valve clearances takes
    a lot more time, though.
    Yes, it sounds very likely to me, 'cause I've already seen an old Renault
    Trafic 1.8 petrol (little van, really crappy - perhaps the most crappy van
    I've ever seen, possibly called another way abroad), which used to burn oil
    if driven over 80KPH. I agree it was true, but no clue about why this
    behaviour (even if I'm pretty sure it has someone to see with higher revs).
     
    G.T, May 2, 2004
    #4
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