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Thread: Diagnosing a blown head gasket

  1. #1
    Join Date
    Apr 2008
    Location
    Bay Area, California
    Posts
    703
    My Cars
    01M5, 99M3 Supercharged

    Diagnosing a blown head gasket

    I converted my VF supercharged S52 M3 to a Link G4x a few months back. I had it tuned for flex fuel and it was driving really well. I had been testing it for almost two months in my local backroads, really beating up on the car and it was performing perfectly. I took it to Thunderhill and on the warmup lap, the headgasket blew between cylinders 4 & 5. Ethanol content was 74%.

    It's worth noting that I was driving the car really conservatively being that it was the warmup lap. I hardly got into boost and I didn't go WOT before the car sounded like a Subaru.

    Also worth noting the car was on a Victor Reinz headgasket with OEM head bolts. I have an Elring gasket going in with ARP head studs.
    PXL_20221104_000128895.jpg PXL_20221104_013944459.jpg

    There looks to be evidence of detonation on cylinder 5. There are also a scratch in the cylinder wall which I can feel with my fingernail.
    PXL_20221104_221557918.jpgPXL_20221104_221346410.jpg

    I'm also seeing damage to the tops of the other pistons near the valve recesses. Could these also be caused by detonation, or maybe piston to valve contact?
    PXL_20221104_220835198.jpg

    I'm just trying to understand what caused this problem so I can obviously prevent it. My first suspicions are maybe the ignition timing was tuned too aggressively. I had been testing the car in hot weather every day. The track day was actually the first day the new tune had seen colder temperatures. Possibly the cooler air charge combined with aggressive timing resulted in detonation?

    I guess my second question is does this damage warrant a rebuild or send it?
    Last edited by illmatik; 11-05-2022 at 01:18 AM.

  2. #2
    Join Date
    Oct 2006
    Location
    Toronto, Canada
    Posts
    3,375
    My Cars
    E36 Turbo
    I saw your post on FB - although the pictures of the logs you posted are useless - one thing is clear, a few things weren't setup correctly by your tuner, such as your target lambda always being .95 at all times, so who knows what else wasn't done right.

  3. #3
    Join Date
    Apr 2008
    Location
    Bay Area, California
    Posts
    703
    My Cars
    01M5, 99M3 Supercharged
    I do think I will be finding another tuner.

    Any thoughts on the scored cylinder wall?

  4. #4
    Join Date
    Feb 2017
    Location
    Raleigh, NC
    Posts
    288
    My Cars
    1998 M3 643whp
    I'd flow check fuel injectors too as your valves aren't consistently bad. Do you have an ethanol sender unit to verify the ethanol content real time? (Assuming that is where the 74% came from).

  5. #5
    Join Date
    Apr 2008
    Location
    Bay Area, California
    Posts
    703
    My Cars
    01M5, 99M3 Supercharged
    Yes, there is an ethanol sensor and the tune is as setup to blend depending on the percentage.

    Injectors are brand new ID1050X.

    At this point, I'm going to put the head on once I get it back from the machine shop and pray the compression numbers are still good. If so, I'll move forward with another tuner. The detonation, loose head bolts and blown headgasket in between cylinders indicates too aggressive of ignition timing to me, but I'm still open to all opinions.

    Sent from my Pixel 6 using Tapatalk

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