Hello there and welcome to the BMW Car Club of America.

If you are a BMW CCA member, please log in and introduce yourself in our Member Introductions section.

Spark Plug Popping out of the head

Discussion in 'R50 Cooper (2001-2006), R52 convertible (2004-2008' started by burroughsct, Feb 2, 2009.

    burroughsct guest

    Post Count: 6
    Likes Received:0
    Has anyone seen a MINI Cooper engine pop a spark plug out of the head? This happended to me on Friday evening and fortunately I wasn't too far from home. I drove the car home on three cylinders and made a call to my mechanic. On Sunday afternoon, he came over and installed a helicoil in the number 2 spark plug hole. Just in case, I made a call to a head remanufacturer down in Clearwater, Florida. I explained to him the situation and he told me that he has seen this several times and that I wasn't the only one. I also found a forum on a MINI website that had owners complaining of the same thing.
    My car is fixed and running fine, but now I am worried that this is going to happen again. Just curious if anyone else has seen this or had this happen to their car.

    Chris
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Wow (for a couple things.)
    Need history:
    Year and model?
    How many miles?
    Have the plugs ever been replaced?
    If so, how many times?

    Also, your mechanic is a bada$$ if he makes housecalls!
    • Member

    granthr

    Post Count: 1,583
    Likes Received:2
    Is your car still under warranty? If so take it to MINI. Let them aware of the problem and have them do a remaining work that needs done.
    • Member

    granthr

    Post Count: 1,583
    Likes Received:2
    Paul, what would cause this? Overboast of the turbo or supercharger? Failed blow off valve? Just a weak head? Poor design? Have you ever seen this on BMWs?
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Never seen it on a car that hasn't had the plugs replaced. Usually, this is caused by over or undertorquing of the plugs when installed. It could very well have been done at the facotry, or be caused by poor castings or improper machining of the threads on the head or plug. Don't feel like doing the math right now, but the pressures inside the cylinder are not really enough to push a plug out of the threads without other factors causing problems in the threads themselves.
    • Member

    granthr

    Post Count: 1,583
    Likes Received:2
    Does over torquing of the plugs weaken the treads and head? When these blow out, do they take the threads with them? What a mess, that would not be a fun repair! :(
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Overtorquing can weaken the threads or just plain strip them out. Generally, unless the plug was very loose before it blew out, all the threads follow and then you need to repair them somehow (I prefer a timesert to a helicoil.)

    burroughsct guest

    Post Count: 6
    Likes Received:0
    Re: MINI Cooper Spark plug popped out

    Car is a 2003 MINI, base model. Car has almost 88,000 miles on the odometer. Car is way out of warranty. Running Bosch Platinum IR Fusion plugs. Plugs were torqued to factory spec when installed on a cold head. The helicoil did the trick and car is running fine. The service engine soon light is still on- I'm hoping it will clear itself but I may have to have it cleared. I've never seen this happen on a BMW engine. Of course, the MINI engine is a Chrysler design made in Brazil by tritec motors. I"ve been told by a couple mechanics it is the way the head was casted.

    burroughsct guest

    Post Count: 6
    Likes Received:0
    MINI Cooper Spark plug popped out

    Yes, my mechanic makes house calls, even on a Sunday. He is awesome.
    • Member

    granthr

    Post Count: 1,583
    Likes Received:2
    You do have an awesome mechanic!! I hope you bought him a case of beer!! :D

    Paul do you prefer time sert because they hold better? Just in this type of situation or all the time?
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    I like timeserts because when chosen and installed properly, they give the sealing washer a continuous surface to seal against. In addition, the get locked into the threads better than the helicoils. Some people don't like them because they supposedly don't have the same heat transfer as helicoils, but if you get the copper coated ones, there is no problem. Really, the helicoils are fine, and you may lose like a half a PSI compression or less. One place I definitly go for a timesert over a helicoil is a drain plug because the top of the helix will never allow the crush washer to seal properly without using oversize washers/lots of gasket sealer.

    burroughsct guest

    Post Count: 6
    Likes Received:0
    Service engine soon light on

    Got the MINI fixed Sunday, but the service engine soon light is on. My mechanic didn't have a scanner with him to reset the light. Will the light go out in a couple of days, or will I need to have him use a scanning tool to turn the light out? I did provide beer with the Sunday house call.
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    You will likely have to get the light reset, since it is probably going to be for a slew of reasons (misfires on that cylinder, lean condition, etc.) Don't make him come to you though :)

    burroughsct guest

    Post Count: 6
    Likes Received:0
    The service engine soon light cleared itself yesterday evening on the drive home so there was no need to clear the light with a scanner.

    Dr Obnxs guest

    Post Count: 122
    Likes Received:1
    Not uncommon

    but not something that happens to everyone. It did happen to me too! Most happen on the S, but a few on the base coopers too. Anyway, the popping plug seems to be linked more to undertorquing than over torquing. Many go up to 22-24 ft lbs for the plug torque and don't have problems. Guys with modded cars like mine tend to check more often. It seems that this is a design "feature" of the Tritec engine. Anyway, the repairs hold well. I personally like the inserts because the steel used for them gives a harder thread than the Al of the head itself.

    Glad the repair went well.

    Matt

Share This Page