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  1. #1
    hebrewdiver
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    overheating on 1998 740il

    I noticed coolant flowing from my car and soon after the pump belt broke and the pump went bad or vise versa. I changed the pump but not the thermostat. After putting the part back together and filling the tank with a coolant water mixture the coolant mixture started flowing out the overflow tank kind of bubbling out. Question 1; could this be the thermostat? Question 2 Do you fill the radiator through the overflow tank? Question 3 Is there a way to bleed this system? Question 4 Can you over tighten the belt of the water pump? Please any help would be appreciated


  2. #2
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    Member No: 78269 claudio512 is an unknown quantity at this point claudio512's Avatar
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    Re: overheating on 1998 740il

    Most likely thermostat is not woking after overheating or was placed backwards... very dangerous because preasure could bust return hose and water is very HOT!! Need to replace thermostat, which it comes on 3 different temperatures, and the lowest is 71F [best on Southern hot states].

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    Member No: 49872 rhunt17 is an unknown quantity at this point rhunt17's Avatar
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    Alway replace the thermostat when changing (m)

    a water pump...

    Yes, there is a bleed screw, though I don't know the exact location.

    Yes, you can tighten the belt too much. I believe a rule of thumb is that you should be able to move the belt about 0.5" to either side...-Reed

  4. #4
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    ETK only lists one thermostat and says it has

    characteristic control

  5. #5
    hebrewdiver
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    Re: overheating on 1998 740il

    Okay I replaced my thermostat and tried to bleed the system. When bleeding I get a spray of hot water until there is nothing but steam coming out of opening never a steady flow of fluid. I tried this with the filler cap on and off. I took off the upper radiator hose to see if fluid was flowing from the hose. I was told this was a way to see if the water pump was working. there was little to no water flow except when water was added to expansion tank. I did not have this problem before I replaced the water pump. May gauge does not show over heating right in the middle. Any way to check to see if the pump is not pumping. Sorry such a long post. Thanks for past and future help

  6. #6
    Will
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    lets go over this slowly... lots of BS here....

    You asked:

    "I noticed coolant flowing from my car and soon after the pump belt broke and the pump went bad or vise versa. I changed the pump but not the thermostat. After putting the part back together and filling the tank with a coolant water mixture the coolant mixture started flowing out the overflow tank kind of bubbling out."

    Okay you put the old thermostat into the new pump and the old thermostat was working when the belt broke? Its probably okay now unless you dropped it or smacked it. Did you drop or smack it??

    What do you mean bubbling out? Was this after the engine warmed up and coolant came out the open fill hole? Of course it's going to do that.

    "Question 1; could this be the thermostat?"
    No

    "Question 2 Do you fill the radiator through the overflow tank?"
    Yep. Or you can beam the water in with a transporter.

    "Question 3 Is there a way to bleed this system?"
    Yep. See www dot e38 dot org. It takes a few hot/cool cycles to get it stabilized again. When cool, fill to the max level (stick flush with top). When hot, with the heater on 90 deg., and with the cap tight on the fill hole, crack the bleed screw and get the air out.

    "Question 4 Can you over tighten the belt of the water pump?"
    Actually, no you cannot overtighten the belt. The belt tightness is determined by the tension actuator. It is not adjustable.

    From other posts:
    "Yes, there is a bleed screw, though I don't know the exact location."
    It is forward of the filler cap on the overflow tank.

    "Yes, you can tighten the belt too much."
    No you can't. That person has never replaced an E38 belt. See above.

    Your follow up:
    "Okay I replaced my thermostat and tried to bleed the system. When bleeding I get a spray of hot water until there is nothing but steam coming out of opening never a steady flow of fluid. I tried this with the filler cap on and off."
    That's bad and shouldn't happen. It should be: coolant topped off when cool, put cap on tightly, run engine til hot, open heater up (90 deg), crack bleed screw, get hissing, then bubbling, done. Repeat 3x.

    "I took off the upper radiator hose to see if fluid was flowing from the hose. I was told this was a way to see if the water pump was working."
    No that's [Oops!]. Don't do that. What a mess. When the engine is cold, very little coolant will flow to the radiator. That is what the thermostat does for a living.

    "there was little to no water flow except when water was added to expansion tank"
    Stop, don't do this to your car. It's going to smell like coolant for a year. Your pump is pumping, don't worry. There is a 3/4 steel shaft, and if the fan is turning so is the impeller. Especially if it is brand new.

    Claudio wrote
    "Most likely thermostat is not woking after overheating or was placed backwards... very dangerous because preasure could bust return hose and water is very HOT!! Need to replace thermostat, which it comes on 3 different temperatures, and the lowest is 71F [best on Southern hot states]."
    That's total [Oops!]. Maybe Claudio is thinking of his Ford. You can't put the Tstat in backwards. If the temp guage is holding at the middle the Tstat is working. You can only get one temperature from the dealer.

    Okay, cheers and good luck,

    Will

  7. #7
    Will
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    BTW, Oops! here stands for b.u.l.l.s.h.i.t


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