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Thread: Overheated, no signs of leak

  1. #1

    Overheated, no signs of leak

    UGH. Just took the garaged z8 for a quick road trip.. It was serviced several months earlier at bmw of the Hamptons after a check engine light revealed an O2 sensor fault. it was replaced and yet again the light came on. It turned out next to be something with the octane sensor and since replaced ran great after 3k expense. Recently last month I noticed a smell of antifreeze or overheated water radiator smell after driving locally around town. I checked the engine but no signs of overheating. Gages were fine. just last week I took the car out and the temp light quickly went on and off after the temp gage went into the red. I parked the car and in the morning after it cooled I put some water in the radiator reservoir. Drove to the BMW dealership about 20 miles with no issues. They did a pressure test and found the system does not hold pressure and they have told me they noticed a water stain on the bell housing and have suggested the car may be leaking from a freeze plug or head gasket. I cant imagine a car that is in a heated and AC garage with 22k miles has this kind of problem. Any suggestions or should I have them attempt a repair. They said the tranny and bell housing has to be removed. The estimated cost is 4k. I think I should just run it for awhile and see if it leaks in the garage. the floors are white so a green antifreeze stain will show up easily. any comments would be great Chris

  2. #2
    The freeze plug diagnosis doesn't sound unreasonable, the cost is another story. If the car wasn't maintained with the proper ratio of antifreeze, I can envision a scenario were corrosion would come into play at a freeze plug. The potential head cover gasket failure is more troubling to me because that could also mean water is seeping into the oil. If you check the the engine oil dipstick, the oil will appear chalky white if there's water into the lubrication system rather than the proper clear and brown appearance.

    From your description, you know there's a coolant leak the only question is exactly where. I would ask for a more thorough analysis at the dealership or repair center and fix the problem. Keep us posted!
    My Best,


    2002 Z8 Jet Black//Sport Red
    2012 SLS AMG Obsidian Black/Classic Red