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    car running hot

    Car is running hot, according to the gauge, I was just a few needle's width from hitting red. Thermostat and radiator is good, water pump is about a year old. Should I flush out the cooling system and run water wetter? This just happened out of nowhere and I had no problems all summer.

    Could it be the gauge? Cause I put in a new cluster about 2 and a half weeks ago. It does start off at cold and gradually goes up to normal then starts getting hot after longer drives in traffic and when I turn on the heater it does seem to cool down so I don't think its that.

    Getting a new thermostat anyways, putting it in tomorrow and if that doesn't work what else could it be?
    sigpic

    #2
    bleed the system change the coolant, watter wetter may help, but then it's just masking the problem. Does it get warm while sitting in traffic, or driving or both?

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      #3
      changed out the thermostat today, flushed and bled the system. checked all hoses and the fan. still hot. anything else it could be?

      runs hot pretty much all the time after about 15-20 minutes of driving. doesn't even cool down much on this mile and a half long hill where I coast down at about 50 mph.
      sigpic

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        #4
        If the engine runs hot when driven at speeds above 35mph, the fan and clutch can be eliminated as suspects. That leaves the radiator, water pump, thermostat, temp sensor, or a head gasket leak as possibilities.

        The temp sensor tends to fail in such a way as to produce completely bogus indications, which doesn't seem to be the case here. So I tend to suspect a different problem.

        A failing thermostat that won't open all the way is possible. Swapping in a new stat, or testing the one in the car, will quickly determine if that is the cause of the overheats.

        Clogged cores in the radiator will cause overheats, but unless the cooling system is pretty dirty or the radiator is well used that's pretty far down on the list. In a like manner water pumps on these engines are rarely the cause of this sort of problem.

        That leaves air in the cooling system as a potential cause. A leaking head gasket can pump air into the system and cause this. A simple test for this condition is to properly bleed the system (procedure below), drive the car until you see the temp spike, and re-bleed. If significant air is released then, the head gasket has failed.

        1) Using ramps or a jack get the front of the car 1' or more higher than
        the rear. That will make the radiator and bleed screw the highest point
        on the engine and facilitate removal of air.

        2) With the bleed screw open, add coolant until no more air comes out of
        the bleed.

        3) Leave the filler cap off, or at least loose, and set the heat for max
        temp and fan speed. Leaving the cap loose will prevent air that's still
        in the system from causing a "coolant fountain" once the engine heats
        up. Start the engine and allow it to warm up to operating temp. As it
        warms up occasionally crack the bleed screw to release any air and top
        up the coolant as necessary.

        4) Once the engine is at temp bring it up to 2000-2500 for a few seconds
        several times. Then crack the bleed until no more air is released. At
        this point the heater should be throwing lots of hot air, which
        indicates that the heater core is filled with coolant. You may have to
        repeat this a few times to get all the air out.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

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          #5
          Originally posted by jlevie View Post
          If the engine runs hot when driven at speeds above 35mph, the fan and clutch can be eliminated as suspects. That leaves the radiator, water pump, thermostat, temp sensor, or a head gasket leak as possibilities.




          .
          Fan isn't needed once at speed (I have seen a few hundred cars with bad fans and clutches that all overheated at idle) if at speed then it is usually water pump

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            #6
            Swapped in my old cluster and everything is good again. Testing out the old gauge tomorrow to make sure that was the problem. Now I have no fuel gauge, I swear it takes 4 clusters to build a good one.

            Thanks for all the suggestions, if it isn't the gauge, I will have to do the water pump cause that is the only thing left.
            sigpic

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              #7
              Lol make sure you didn't loose the ground nut for the fuel gauge or the temp gauge it will make them read incorrect, and true about have to have 4 to make one good one, it took 3 for me!

              1986 325es (69k) Garage Queen Buy It Now 10k;1986 325es (track rat) 2.7i How-To & 1.1/1.3Motronic UpGrade
              1991 318is (daily driver) 1991 318is M42 Maintenance How-To;1989 325i (parts car)

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