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Troubleshooting Overheating


      
      
-----Original Message-----

      From: Chris
      Manderson

      Sent: Monday, March 18, 2002 12:02 PM

      To: gopostal@seniorsix.org

      Subject: Overheating: whaddya gonna do... bleed on me?

      
      
Gruppen,

      
      
Thanks to all who offered advice on the overheating
      problem. Turns out that a good bleeding was all the system
      needed. I'm sure King George III's doctors would have offered
      the same advice.

      
      

      
      

      
      

      
      
Art Wegweiser wrote:

      
      
Charlie seems to have covered everything I can think of
      with regard to an overheating problem. Excellent coverage of
      most possibilities.

      
      
All I can add is my redundant get a "NINE BLADE FAN"
      mantra and replace the dumb slotted bleeder screw with a hex
      bolt.

      
      
Always use Never-Seize on almost everything except,
      maybe, the screws that hold your door ashtray in place, another
      dumb piece of design that any former or present smoker will
      understand why. I can't think of any other possible use for the
      thing except holding small licorice and beef jerky sticks or
      rolled up dollar bills for paying tolls and for stashing the
      many screws, nuts and washers that appear out of nowhere on
      your floor.

      
      
Art

      
      

      
      

      
      

      
      
At 1:41 PM -0500 3/15/02, cgshawaii@netscape.net
      wrote:

      
      
Chris
         Manderson
         wrote:
         
         
What are the signs of water
         pump failure? My 2800CS had a leaking 3-row radiator, which
         I replaced with a stock E-12 radiator. No leaks, but the
         overheating has not stopped.

         
         
1. Is this water pump failure;
         or

         
         
2. could the E12 radiator be
         shot as well (came from a parts car, was going to re-core it
         but this happened); or

         
         
3. Is it something
         else?

      
      
1. Probably not.

      
      
2. This is a possibility

      
      
3. This is also possible. Read on.

      
      
There's not enough information to define a solution.
      That you installed a used rad in unstated condition makes the
      rad suspect. OTOH, the usual failure mode of a water pump is
      first for the shaft seal to leak and show a drip or dribble
      from the little hole below the shaft. Hard to see, gotta look
      up from under, don't get coolant in your eyes/face. 

      
      
Next the bearing rusts and gets wobbly. In a far gone
      case, the pulley and fan will be wobbly, and the fan might even
      hit the rad. 

      
      
A casual touch will not reveal this because belt tension
      keeps everything snug, but it may "cluck" once or twice at
      startup and shutdown, losing water all the while. A firm grasp
      and shake will show you that it's a goner.

      
      
So, water pumps really don't fail to pump, as long as
      the belt still turns them.

      
      
Radiator tube clogging is another matter, and there are
      several ways you can check this out. When the car's warm and
      shut off, the upper and lower hoses should be nearly the same
      temp. No portion of the radiator should be cooler than another.
      This can be checked by hand or better, with one of them
      newfangled infrared "guns" that read temp from a distance. Due
      to cost (start about $100) only the pros and techs usually have
      these.

      
      
Ignition timing also has an effect on engine temp. I
      think that your problem may be more simple, and suggest that
      you make real sure that you've bled
      the system adequately. Make sure the bleed screw hole is clear
      and actually bleeds the system. They tend to scale over inside,
      remove the screw (cooling system depressurized first, please)
      and if water doesn't come out, open the hole using a paper clip
      or small drill. Get the coupe nose up on a slope and, engine
      running, coolant warm and expansion tank cap on tight, open the
      bleed screw and run some coolant out. Just like bleeding
      brakes, there should be no bubbles.

      
      
There is one more opportunity: the thermostat is not
      opening. I can't speak to the frequency of this happening, but
      you can easily remove it and test it by dunking it boiling
      water then cold water. The motion should be easily
      visible.

      
      
All in all, I suggest you bleed first, check rad second,
      thermostat last.

      
      
Charlie

      BMW CCHawaii