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5089E28 overheating issues

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  • Larry R.
    Aug 15, 2007
      I have found a couple things that contribute to most all BMWs to overheat.

      1. Use of the wrong formula fluid.

      Never use the cheap green fluid. BMW spec fluid does not have phosphates because phosphates react to the aluminum that is in the heater core and internal to the radiator. Over time it corrodes and creates a white sort of powder that clogs up the internal fins. It is one reason many older BMWs blow out the heater cores and lose cooling power.

      In Dallas, I've found that GM Dextron formula (orange or purple) that is marked as NO PHOSPHATEs is the best way to go. GM extended their warranty to 100K miles on the cars and trucks and found the green crap was rotting the intake manifolds which were aluminum and so they now require you to use the proper fluid of they can deny warranty claims.

      BMW dealership fluid is purple.

      If you can find a real repair shop that can acid clean your radiator to insure it moves the fluid properly that would be a good effort and should not be that cheap.

      2. Second biggest issue is to not properly bleed the air from the system as noted in another post. you need to get the car to operating temp and then open the 10mm bolt on top the thermostat housing. I have found it takes 2-3 cycles of bleeding to get all the air out of the system. I have found letting the car sit to cool down helps to draw air to the top of the housing to bleed faster in between cycles.

      Did you drain the block from the bottom of the engine of just undo the lower radiator hose or unscrew the nut on the bottom of the radiator?

      3. Overflow tank cap. If you have had an overheating issue, replace it. Yes it is not cheap to find new but well worth it to find one and replace it. Otherwise the fluid will not be able to go to the overflow tank when needed and as designed.

      Is the gauge reading hot or is the car actually boiling over? Both are different items to diagnose.

      4. Fan clutch is critical and hopefully yours is running correctly. I see you updated that according to the email by bypassing the temp control but clutches can be an issue if they are not working. I know I saw a fix where they forced the clutch to work full time and not disengage. Many people replace the fan clutch when they replace the water pump since it is apart anyway and makes labor sense to do so.

      I had a 528e that kept overheating until I replaced the overflow tank and cap (along with finding a like new radiator in a junk car that actually had the smaller hose to the overflow tank. The original one had been capped off as they tend to deteriorate from the documented heat that the engines produce which require the cars to be cooled so much.

      Did you also check the a/c condenser to make sure that those vanes were also clear? If air cannot make it to the radiator in the first place due to dust and debris, that will be a problem. A good air hose nozzle can blow that crap from the engine side out just to make certain. I also blew out my fins on the radiator to make sure it was not clogged by dust prior to installation.

      Hopefully something in here works to get yours running cooler!

      Larry in Dallas where it can get to 100 F degrees in the spring!
      1988 535is Schwartz (among other ones)

      bmwe28@... wrote: Topics in this digest:

      1.1. 528e overheating
      From: elswwjd316
      1.2. Re: 528e overheating
      From: markie_markd

      Messages
      ________________________________________________________________________

      1.1. 528e overheating
      Posted by: "elswwjd316" estodghill@... elswwjd316
      Date: Tue Aug 14, 2007 3:30 pm

      I have a 528e which still overheats after doing the following:

      Replaced head gasket and checked flatness of head and block.
      Flushing radiator and block.
      Removing thermostat, testing, then replacing with new.
      Bypassing fan thermostatic switches to force fan to run at high speed
      full time.
      New water pump.
      Bled all air out of cooling system.
      No leaks.

      Any suggestions?

      Many thanks to the group.



      Messages in this topic (2)
      ________________________________________________________________________

      1.2. Re: 528e overheating
      Posted by: "markie_markd" markie_markd@... markie_markd
      Date: Wed Aug 15, 2007 1:36 am

      sometimes you need to jack up the drivers side part of the car and
      bleed it since air can be trapped in that point of the system, what
      about the clutch fan?



      --- In bmwe28@..., "elswwjd316" wrote:
      >
      > I have a 528e which still overheats after doing the following:
      >
      > Replaced head gasket and checked flatness of head and block.
      > Flushing radiator and block.
      > Removing thermostat, testing, then replacing with new.
      > Bypassing fan thermostatic switches to force fan to run at high speed
      > full time.
      > New water pump.
      > Bled all air out of cooling system.
      > No leaks.
      >
      > Any suggestions?
      >
      > Many thanks to the group.
      >


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