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Thread: Two separate e46 issues, would love help DXing

  1. #1
    Junior Member
    Join Date
    Apr 2017

    Two separate e46 issues, would love help DXing

    First thing (more urgent): This car always has issues but then stops having them so I think itís fine. Another one reared itís head yesterday. Noticed a wet spot under my car that was large enough to make me think it wasnít related to my car and so I thought nothing of it. Drove home today and coolant light came on, and then turned off. Checked the expansion tank, bone dry. Refilled, turned the car on, no leaks anywhere. The temp gauge sits just under top dead center when it warms up, and the heater wasnít blowing hot. (Until this morning when it kind of did...). There was also the telltale white crust under the expansion tank cap like it was leaking from the top. My suspicion is a slowly failing thermostat, but other posts elsewhere said a failing thermostat shouldn't cause any kind of coolant loss of that level.

    Second thing: When I leave the car in park, the gear warning light next to the gear indicator on the dash lights up. This happens about 10 seconds, seemingly after what I would imagine is the ECU running through different circuits in the car. If I put it in drive immediately, the car drives perfectly. I was told by a shadetree mechanic that he's seen it before, and he thinks its a vacuum leak somewhere thats causing the warning light to pop. I was told I have a bad DISA, so I've bought a replacement for that. Does a vacuum leak sound right to you?

  2. #2
    Senior Member
    Join Date
    Dec 2004
    Fairplay, MD
    There's not a lot of tech activity here, so I suggest trying an E46 specific site maybe bimmerfest or E46 fanatics. If the DISA seal if bad that could cause vacuum leak. DISAs do go bad so if you've got one replace it, but it would have nothing to do with transmission light. Not sure on that one. The E46 cooling system is prone to failure at many points. Do not drive the car with no coolant in the expansion tank! Also fill the tank only to the cold level mark when it's cold! If the cooling parts are old, the system is do for a complete change - thermostat, water pump, expansion tank, hoses, etc. Various Roundel advertisers sell kits. Check belts, pulleys, etc while you're in there.

  3. #3
    Senior Member John in VA's Avatar
    Join Date
    Jan 2005
    I've never dealt with a DISA valve or thermostat issues on my E46s, but here is a DISA solution without buying a complete valve:


    Re: cooling system - never had a problem with coolant coming out the expansion tank cap, but it is so common to have a hard-to-see longitudinal crack in the tank, often only detectable when it is hot & leaking. The connector at the bottom of the tank is also a weak point, especially if you're working with non-BMW parts, no matter the manufacturer. The cooling system is the one place to spring for dealer-provided parts.

    You also need to bleed the system of air properly:

    Good luck!
    John in VA

    '74 2002tii
    '85 535i
    '86 535i
    '00 328i
    '02 325xi
    '03 530i
    '06 330ci ZHP
    '15 228i M Sport

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