Engine & Gearbox Heres a weird one.... broken oil cap in the engine block.

Discussion in '1st Generation (2004-2011)' started by colinbos, Friday 14th Aug, 2015.

  1. colinbos Club Member ★ ☆ ☆ ☆ ☆

    I've just returned from a 1000+ mile round trip pulling my caravan from Merseyside to Cornwall, Dorset and Gloucestershire and back, pulled like a dream all the way, plenty of torque etc etc. 2.2CTDI 2006 with 89k miles on.

    I pulled up on the drive at home and noticed a puff of smoke come from under the bonnet on the drivers side windscreen. Opened the bonnet and saw oil spewed under the bonnet, the ABS, the strut, the water reservoir and brake reservoir etc. The cap was sat 'upside down' on top of the hole it was supposed to plug ! It has snapped on the screw part and has some how flipped itself over sitting nicely bothering no one.

    Obviously the oil on the engine block has come out the filler hole around the upturned cap. Not a lot of oil lost at all.

    The question is, would an oil cap snap because of the engine being under pressure whilst towing ? Could the engine pressure cause such a problem?

    or have I just tightened it too much and the engine being run so long coming home (9hrs) the oil filler hole has expanded and snapped it. Bizarre circumstances.

    No oil warning lights, no engine overheat issues (the gauge never moved at all when towing) and no loss of power. No issues at all in fact. Weird.

    All theories welcomed.
  2. Dave Club Veteran ★ ★ ★ ★ ★

    Very strange I'd maybe go for overtightened and the heat caused by the long constant running.
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  3. colinbos Club Member ★ ☆ ☆ ☆ ☆

    I would like to think that Dave, the cap has always been tight to get off so that theory would fit.

    Thanks for your input.
  4. Nels Moderator Staff Team

    That is a strange one! If it was a pressure build up, then I would have expected other signs.
    I think, as @Dave has said, it was from an over tightened filler cap.

    Any other ideas @Evangelists ?
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  5. John Dickson Club Veteran ★ ★ ★ ★ ★

    I'd go with over tightened filler cap. Or perhaps the cap had a slight manufacturing defect- hairline crack or something and it's just taken till this time to develop further?

    I'm no expert so please tell me if I'm talking rubbish but would excess pressure in the sump not vent via crankcase breather pipe?
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  6. Harvey Club Veteran ★ ★ ★ ★ ★

    I would go with that theory @John Dickson, through the breather or PCV system.

    However high oil pressure would be caused by excessively tightened conrod bearing caps and big end bearings, as far as my mechanical knowledge of engines go, unless of course they expanded slightly during 9 hours of operation, but I highly doubt that.

    I would put it down to an over tight filler cap with a hair line crack in it, from either dropping or manufacturing error.
    Last edited: Friday 14th Aug, 2015
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  7. colinbos Club Member ★ ☆ ☆ ☆ ☆

    Many thanks all. Good logical theories.

    I have no other warning signs or indicators the car is 'ill', the opposite in fact. Excellent MPG towing a heavy caravan (33mpg on average) and if I was crazy, it would pull at 70mph easy. No warning or alerts in cooling or oils and as I said the oil level is still showing just below full (a mm or two below).

    Ill keep an eye on it and report back if I have anything else to update on.
    Harvey likes this.
  8. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
    I'd imagine the cap being over tight and a hairline crack developing into something much more should explain it.

    Quite a freak occurrence though.
  9. colinbos Club Member ★ ☆ ☆ ☆ ☆

    Bizarre indeed.
    Im glad no one else has experienced a problem, it means mine isn't one !

    Thanks again guys.

    Happy 'Hondaing'
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  10. garf8v Club Member ★ ☆ ☆ ☆ ☆

    It may be a crack at the threadline,, and when the rocker cover has expanded with the heat, it would constrict round the cap threads, and pop the top off. I had similar with one big end cap bolt some years ago, it sheared where the thread ended, presumably where the torque has maximum turning effect and weakens the metal.
  11. colinbos Club Member ★ ☆ ☆ ☆ ☆

    That's where it broke Garf8v, right on the thread line. No fragments, just a clean break.

    I can't get one until Tuesday so I've epoxy glued it and put it back on loosely but enough to stop oil coming out until then.
  12. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
    Might be worth doing an oil change, just incase any fragments have fallen into the engine.
  13. colinbos Club Member ★ ☆ ☆ ☆ ☆

    Good suggestion SpeedyGee. The break was clean and the two pieces fit together with no gaps, but better safe than sorry.

    I use National Tyres for my interval oil changes. IE: pre inspection and annual service. £25 all in. Keep that cam chain clean and contaminant free.
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