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M20 Bleeding Cooling System Hell...

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    M20 Bleeding Cooling System Hell...

    Background:

    Car ran at perfect temp prior to timing belt/water pump replacement

    Replaced:
    1. Timing Belt tensioner
    2. Timing Belt
    3. Water Pump
    4. Thermostat
    5. Fan and Fan Clutch


    Put everything back together and attempted to bleed system...

    Per the directions:


    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.

    Car was up on ramps


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

    I filled the expansion tank with almost a full gallon of fluid but coolant never came out of the opened bleeder screw (I removed it completely).

    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.

    Heater was on full blast. The only thing exiting the bleeder screw is steam.
    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.

    Revving the motor will result in intermittent fluid and then steam again.


    Other notes:
    1. Temp will get almost to red (I shut it off before it hit that point)
    2. Heat was blowing hot but is now blowing cold despite engine being fully hot
    3. All Radiator hoses are hot except the lowest most radiator hose as bottom of radiator
    4. Radiator itself not hot (cool to touch) despite the steam and engine temperature.

    Help?
    1989 325i Cabriolet Auto
    1990 325i Coupe Auto (sold)
    1987 325i Cabriolet Manual (sold)
    1989 325i Cabriolet Auto (sold)
    1991 325i Coupe Auto (sold)
    1991 325i Cabriolet Manual (sold)
    1991 325i Coupe Auto (sold)
    1990 325i Sedan Auto (sold)
    1984 318i Coupe Auto (sold)

    #2
    are you 100% positive that the thermostat is pointed in the right direction?
    sigpic

    Comment


      #3
      Spring side towards the inside (towards engine and not removable cover).
      1989 325i Cabriolet Auto
      1990 325i Coupe Auto (sold)
      1987 325i Cabriolet Manual (sold)
      1989 325i Cabriolet Auto (sold)
      1991 325i Coupe Auto (sold)
      1991 325i Cabriolet Manual (sold)
      1991 325i Coupe Auto (sold)
      1990 325i Sedan Auto (sold)
      1984 318i Coupe Auto (sold)

      Comment


        #4
        so weird. those are all the symptoms of backwards thermo.

        maybe there's a kink in one of the hoses to the heater core?
        sigpic

        Comment


          #5
          I didn't replace/remove any of the heater core hoses.
          1989 325i Cabriolet Auto
          1990 325i Coupe Auto (sold)
          1987 325i Cabriolet Manual (sold)
          1989 325i Cabriolet Auto (sold)
          1991 325i Coupe Auto (sold)
          1991 325i Cabriolet Manual (sold)
          1991 325i Coupe Auto (sold)
          1990 325i Sedan Auto (sold)
          1984 318i Coupe Auto (sold)

          Comment


            #6
            you still have air if your heater isn't blowing hot.
            this has worked for me.

            Comment


              #7
              are you sure youre not leaking any?

              Comment


                #8
                I don't think so... But I will double check this week. Also buying a pump as suggested above.
                1989 325i Cabriolet Auto
                1990 325i Coupe Auto (sold)
                1987 325i Cabriolet Manual (sold)
                1989 325i Cabriolet Auto (sold)
                1991 325i Coupe Auto (sold)
                1991 325i Cabriolet Manual (sold)
                1991 325i Coupe Auto (sold)
                1990 325i Sedan Auto (sold)
                1984 318i Coupe Auto (sold)

                Comment


                  #9
                  You don't need a pump. Just use a funnel with a piece of tygon tubing and add coolant to the side nipple. You need to do this slowly and massage the upper radiator hose to get most of the air out. You will need to repeat the procedure multiple times with the engine running in between using Jlevie's procedure or the one in Efficient's link. Also, get yourself an IR thermometer to get accurate temp reading of the engine. A small trapped air pocket in the thermostat housing can get the temp needle into the red zone even though your engine is fine. Drill a small hole in the t-stat upper plate can help avoiding this situation.

                  Comment


                    #10
                    Did the pump method. Easy and job done. Should have done this to start with.
                    1989 325i Cabriolet Auto
                    1990 325i Coupe Auto (sold)
                    1987 325i Cabriolet Manual (sold)
                    1989 325i Cabriolet Auto (sold)
                    1991 325i Coupe Auto (sold)
                    1991 325i Cabriolet Manual (sold)
                    1991 325i Coupe Auto (sold)
                    1990 325i Sedan Auto (sold)
                    1984 318i Coupe Auto (sold)

                    Comment

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