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Spark Plugs Broke, Why?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by DougK20, Feb 22, 2003.

  1. DougK20

    DougK20 1/2 ton status

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    I was driving home from work today and spark plug #3 and #4 broke their tops off. Why? I replaced all 8 two months ago! The motor instantly ran like crap. I limped it home and popped the hood. I found the wires just hanging down with the plug tops still in them. Are these bad plugs, or can something cause this? /forums/images/graemlins/1zhelp.gif
     
  2. xnoahx

    xnoahx 1/2 ton status

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    that sounds pretty strange, could you have hit them recently or maybe weakened them when you were installing them?
     
  3. Hossbaby50

    Hossbaby50 3/4 ton status

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    The only time I have ever broke spark plugs was when I was removing them. I didn't use the spark plug socket, and I was trying to get out one of the back cylinders (#7 & #8) and I twisted the ratchet enought to break the plug.

    You might have cracked them when you put them in (not knowing it) and some bump in the road, or something might have finished them off and they came apart.
     
  4. DougK20

    DougK20 1/2 ton status

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    I pulled the plugs to replace and found that the tips had unscrewed and come off. They are Bosch Platinum's p.n. HR9BPX. I can't just screw them back on because it damaged the threads coming off. Dumb design! Thanks for all your suggestions! I'll watch what I buy and how I install more closely! Doug
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    My neighbor had that happen on his Austin Healey. Think he was using cheapy auto-lites though.

    I had two out of 8 auto-lites fail in less than 40 minutes of run time, so you can bet I'm not using them again.

    My Olds motor had Bosch platinums in it when I bought it, the CCC carb was running full rich (try 10MPG freeway with OD and a 307, thats what a failed ECM will get you) on that thing for MONTHS while I drove it, and when I pulled the plugs, they weren't fouled at all. I was fairly impressed actually.
     

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